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Recent advances in bacteriology with special reference to food
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R E C E N T A D V A N C E S IN B A C T E R I O L O G Y S P E C I A L R E F E R E N C E TO FOOD.*
[ J. F. I..
wrru
BV M. V. ]]ALL, M.D.
T h e lecturer was introduced b y the S e c r e t a r y of the Institute, and spoke as follows : MEMBERS OF THE INSTITUTE, LADIES AND GENTLEMEN: B a c t e r i o l o g y is, comparatively, a r e c e n t science. Only within the last ten y e a r s has it received any special atten. tion, and within this time it has b e e n given a place in t h e medical colleges and b e c o m e r e c o g n i s e d as an i m p o r t a n t d e p a r t m e n t of knowledge. Municipalties are f o r m i n g laboratories for bacteriological work, and g o v e r n m e n t s are instituting, on a large scale, researches, which m u s t e v e n t u a l l y be of g r e a t service to mankind. It is h a r d l y to be expected t h a t this s u b j e c t should as y e t be the c o m m o n p r o p e r t y of a n y b u t those w h o have m a d e it a special study, and, therefore, a few words as to the n a t u r e of bacteria will not be o u t of place here. B a c t e r i a - - f r o m the Greek, m e a n i n g little or m i n u t e rods - - i s a term applied to various forms of organisms, micrcscopic in size, closely allied to the lower t y p e s of fungi and algae ; u s u a l l y c o n t a i n i n g no chlorophyll ; capable, in m a n y instances, of propelling t h e m s e l v e s w i t h swift motion t h r o u g h the liquids in which t h e y are found, and possessing, for this purpose, small cilia or flagella, like o t h e r t y p e s of microscopic plants. T h e y are very minute, r e q u i r i n g for their detection p o w e r f u l lenses. S o m e idea of their size m a y be o b t a i n e d from t h e s t a t e m e n t t h a t in the space of an inch from 15,oo0 to 2o,0oo can be placed side b y side; but, g r o w i n g t o g e t h e r in large n u m b e r s as t h e y do, such a g g r e g a t i o n s or colonies can readily be seen with the u n a i d e d eye, t h o u g h the i n d i v i d u a l m e m b e r s of these colonies cannot be reeognised. *A lecture delivered before the Franklin Institute.
Nov., x895.]
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Bacteria are n e i t h e r y e a s t s nor moulds, t h o u g h possessing some of the characters of both. T h e name, " b a c t e r i a , " is not a good one, since o t h e r t h a n rod-shaped o r g a n i s m s are collected u n d e r this group. Microeocei are g l o b u l a r or spherical b a c t e r i a ; bacilli are the rod-shaped bacteria ; and spirilli are spiral-formed or t w i s t e d bacteria. T h e colonies of one form are not to be disting u i s h e d from the others, b u t u n d e r t h e microscope the dif_ ferenee in shape is readily m a d e out. Bacteria are quick breeders ; t h e y m u l t i p l y very rapidly. F r o m one or two g e r m s t h o u s a n d s are o b t a i n e d in t h e course of a few hours. Some one has m a d e the calculation t h a t a single germ, if u n i n t e r r u p t e d in its growth, w o u l d fill an ocean with its p r o g e n y in five days ; but, f o r t u n a t e l y , it digs its own g r a v e by the poisons it generates, and so p u t s a l i m i t to its g r o w t h . Some require several days before germin a t i o n occurs. T w o kinds of g r o w t h are k n o w n : one, in which r e p r o d u c t i o n is a process of fission or s e g m e n t a t i o n - - o n e b a c t e r i u m d i v i d i n g itself into two, a n d each of these a g a i n s u b - d i v i d i n g - - i n reality, a c o n t i n u a t i o n r a t h e r t h a n a reproduction. _And a second kind, k n o w n as sporulation. T h e g e r m gives rise to a spore, the spore t h e n takes on a s e p a r a t e existence and, w h e n the conditions favorable to m a t u r a t i o n exist, it gives rise to a n e w germ. Both forms of g r o w t h are utilised by the same b a c t e r i u m . U n d e r o r d i n a r y conditions it m u l t i p l i e s by fission w h e n a p e r m a n e n t form is a d v a n t a g e o u s , or, as some think, w h e n t h e soil is p a r t i c u l a r l y rich, it p r o d u c e s spores. Spores h a v e n o t been f o u n d in all b a c t e r i a ; those possessing t h e m are v e r y r e s i s t a n t to all physical and chemical agencies, and w i t h s t a n d a h i g h degree of h e a t w i t h o u t b e i n g destroyed. F o r the different b a c t e r i a different conditions are neces_ sary. J u s t as different p l a n t s r e q u i r e different kinds of soil a n d t e m p e r a t u r e , so these m i n u t e p l a n t s react differently a n d d e m a n d for t h e i r g r o w t h v a r i o u s s u r r o u n d i n g s . Some are n o t at all particular, a n d flourish on a n y sort of soil. T h e y are like weeds t h a t grow w i t h o u t a t t e n t i o n ; others a g a i n are as sensitive as hot-house plants, and require very carefully p r e p a r e d m e d i a a n d a s u i t a b l y r e g u l a t e d t e m p e r a -
342
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ture. W h i l e s om e species d e m a n d a p l e n t i f u l s u p p l y of o x y g e n , o t h e r s g r o w o n l y w h e n this is excluded. S u n l i g h t is u s u a l l y d e s t r u c t i v e ; an alkaline m e d i u m is b e t t e r tolerated, t h a n a n e u t r a l one, a n d acids are u s u a l l y h a r m f u l . M o i s t u r e is n e c e s s a r y to g r o w t h . B a c t e r i a are n o t onl y disease-producers, t h e y manuf a c t u r e a h o s t of p r o d u c t s beneficial a n d essential to life. L i fe itself d ep ends , in a g r e a t m e a s u r e , u p o n t h e act i ons of t h e s e m i n u t e plants, w h i c h t r a n s f o r m t h e c o m p l e x molecules into t h e i r e l e m e n t s and m a k e t h e m fit for assimilation. If we could s e p a r a t e t he i n d u s t r i a l g e r m s f r o m t he p a t h o g e n i c or disease-producers, a n d d o m e s t i c a t e t h e former, while we d r i ve t h e l a t t e r out of existence, life w oul d be m o r e w o r t h t he living. T h i s is g r a d u a l l y b e i n g att e m p t e d . S c i e n t i s t s are p o i n t i n g o u t to us t h e p r o p e r t i e s of i n d i v i d u a l v a r i et i es , a nd s h o w i n g us t h e m e t h o d s of cult i v a t i o n ; while h y g i e n i s t s a n d t h e r a p e u t i s t s are d o i n g all t h e y can to e x t e r m i n a t e t he d e s t r o y e r s of life; so t h a t we can a l r e a d y see how, in a few years, c h o l e r a will be a r a r e disease, and t u b e r c u l o s i s will no m o r e be c o u n t e d as t h e c a u s e of one-fifth of all deaths. W h a t advances, if any, h a v e b e e n m a d e in r e c e n t y e a r s as r e l a t e s to t h e s u b j e c t of foods ? T h i s is t h e topic I h a v e b e e n asked to c o n s i d e r : " B a c t e r i a in t h e i r r e l a t i o n to food ?" F i r s t of all, I desire to t a k e up t h e m o s t i m p o r t a n t of foods, n amely , water. W a t e r is a food b e c a u s e it is nece s s a r y to s u s t a i n life, a n d c o n s i d e r e d in this sense air m i g h t also b e classed as a food. B u t w h e t h e r or n o t we call w a t e r a food, t h e r e are o t h e r r e a s o n s sufficient for us to m a k e it a m a t t e r for c o n s i d e r a t i o n here. F o r m e r l y a good w a t e r was one w h i c h c a m e up to a certain chemical standard. T h e a m o u n t of c h l o r i d e s and n i t r a t e s was d e t e r m i n e d , t h e h a r d n e s s was c o m p u t e d and t h e t o t a l a m o u n t of solids a s c e r t a i n e d . If a w a t e r did n o t c o n t a i n m o r e t h a n I g r a i n of c h l o r i n e p e r gallon, it was d e e m e d p o tab le. T o- da y, while c h e m i c a l anal ysi s still has an i m p o r t a n t place in t h e e x a m i n a t i o n of water, it m u s t go h a n d - i n - h a n d w i t h t h e biological or b a c t e r i o l o g i c a l analysis,
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and we m u s t k n o w w h a t sort of living o r g a n i s m s i n h a b i t or are to be found in t h e specimen in question. In the early days of b a c t e r i o l o g y m u c h stress was laid u p o n the n u m b e r of b a c t e r i a f o u n d in a given q u a n t i t y of water, and w a t e r c o n t a i n i n g m o r e t h a n 5oo colonies to t h e cubic c e n t i m e t e r was d e e m e d unfit for drinking, b u t n o w it is n o t so m u c h the q u a n t i t y as the q u a l i t y of the b a c t e r i a that is looked for. One t y p h o i d bacillus in a gallon of w a t e r is m o r e d a n g e r o u s than one million ordinary w a t e r b a c t e r i a ; in fact, it w o u l d r e n d e r the w a t e r impotable, while the l a t t e r w o u l d be harmless. T h u s , the w a t e r a n a l y s t of to-day m u s t be a c o m p e t e n t b a c t e r i o l o g i s t as well as c h e m i s t ; and to b e a b a c t e r i o l o g i s t m e a n s a p a t h o l o g i s t as well, for, in the i n v e s t i g a t i o n of bacteria, animals m u s t be u s e d for experiment, and t h e n a t u r e of the diseases caused b y t h e b a c t e r i a m u s t b e k n o w n to the experimenter. As in t h e earlier chemical analyses, t h e chlorine itself w a s not considered d a n g e r o u s , b u t simply one of the indications of faecal c o n t a m i n a t i o n , so in the bacterial examination, t h e presence of certain h a r m l e s s g e r m s m a y indicate d a n g e r o u s c o n t a m i n a t i o n s . F o r instance, the presence of t h e bacilli c o m m o n l y f o u n d in h u m a n faeces, w h i c h in themselves are non-pathogenic, would, of course, lead one to infer t h a t h u m a n s e w a g e h a d b e c o m e m i x e d with the w a t e r supply. T h e m e t h o d s for t h e d e t e c t i o n of t y p h o i d bacilli in drinking-water leave m u c h to b e desired. T h e e x a m i n a t i o n is often u n d e r t a k e n too late, w h e n the bacilli are no longer present,or h a v e b e e n d e s t r o y e d b y the ordinary w a t e r bacteria. T y p h o i d bacilli do n o t live l o n g in ordinary drinking-water; and yet, if t h e w a t e r be c o n t a m i n a t e d with them, a w h o l e city or d i s t r i c t can b e c o m e i n f e c t e d in a s h o r t time, and w h e n suspicion is directed to the w a t e r the g e r m s have disappeared. T o . a less degree, this is likewise true of t h e cholera spirillum, w h i c h acts so q u i c k l y and is so deadly, a n d w h i c h u s u a l l y is spread t h r o u g h t h e drinking-water. A m e t h o d lately described, and w h i c h p r o m i s e s success, is to take a large q u a n t i t y of t h e s u s p e c t e d w a t e r (200 cubic centimeters), and add to it 2 g r a m s of p e p t o n e and 2 g r a m s of
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chloride of sodium. Place this in the i n c u b a t i n g oven, and, if cholera g e r m s are present, t h e y will m u l t i p l y rapidly, so t h a t t h e y can readily be d e t e c t e d in the course of ten to twelve hours. Bacteric e x a m i n a t i o n s have been m o s t useful in the testing of water filters, " g e r m - p r o o f " filters, etc. Several filters are now in the market, which claim to be germ-proof ; t h a t is to say, which are supposed to p r e v e n t the passage of bacteria t h r o u g h the very m i n u t e pores of the filter. T h e s e filters are made of baked clay, infusorial earth, porcelain, etc. As a rule, t h e y can deliver a g e r m l e s s w a t e r only for a few d a y s in succession, when, o w i n g to the a c t i v i t y of the b a c t e r i a which have collected on the surface of the filter Cylinder, the pores are p e n e t r a t e d by the g r o w t h , and more b a c t e r i a t h a n usual find t h e i r w a y into the water. This, in some cases, can be p r e v e n t e d by a careful cleansing, every few days, of the filter tube. All t u b e s are not alike, and some afford no protection at all, t h o u g h t h e y clarify the w a t e r by k e e p i n g out the grosser particles of dirt. Filters are best tested by a d d i n g to the water, before filtration, some well-known b a c t e r i u m (usually the red pigm e n t - f o r m i n g and r a p i d - g r o w i n g Bacillus prodiKiosus ) m a k i n g c u l t u r e s before and t h e n after filtration. If, u n d e r suitable precautions, the g e r m is f o u n d p r e s e n t in the filtered water, t h e filter is imperfect. In the t e s t i n g of large filtering plants, where it is not e x p e c t e d t h a t t h e w a t e r will be perfectly free from germs, q u a n t i t a t i v e m e t h o d s m u s t be used, in order to tell w h a t p e r c e n t a g e of b a c t e r i a is left behind. T h e s e large filtering p l a n t s are in use in several cities, and, it seems to me, t h e y are of d o u b t f u l value only. It is true, the w a t e r is more p l e a s i n g to the eye, and, for toilet a n d l a u n d r y purposes, more v a l u a b l e ; b u t if the w a t e r is c o n t a m i n a t e d w i t h disease g e r m s there is no s u r e t y t h a t t h e y will be a m o n g the 50 per cent. filtered out. T h e y are j u s t as liable to pass t h r o u g h as the others, and such a w a t e r is not safe. F r o m the s a n i t a r y p o i n t of view, filtering plants are only v a l u a b l e w h e n the w a t e r is u n c o n t a m i n a t e d by h u m a n s e w a g e ; a n d to erect such a p l a n t in our city, w i t h o u t p a y i n g a n y a t t e n t i o n to the s o u r c e of our w a t e r
Nov.. t895.]
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supply, and even allowing it to be p o l l u t e d along its whole course, will h a r d l y reduce the d e a t h rate, t h o u g h it m a y add to the aesthetic q u a l i t y of the water. On an average, 5oo d e a t h s occur every year in this city from t y p h o i d fever. T h i s m e a n s at least 6,ooo cases. F r o m an economic point of view, t h e persons affected are the most valuable m e m b e r s of society, chiefly y o u n g adults b e t w e e n the ages of 2o and 4o. T h e expense, in loss of time, medical a t t e n d a n c e , etc., is at least $ioo for each case, a total cost of $6oo,ooo y e a r l y from this one disease, to say n o t h i n g a b o u t the loss of life; and all because we are obliged to d r i n k the s e w a g e of half a dozen t o w n s above us, a n d the d r a i n i n g s from g r a v e y a r d s and pigsties along the banks of the Schuylkill. A n d while we are t h u s t r e a t e d by the cities above us, we s e n d our sewage to the t o w n s below. Some strict m e a s u r e s m u s t be p u t into practice, w h i c h will p r e v e n t this p o l l u t i o n of our drinking-water. T h e second i m p o r t a n t article of food, with w h i c h bacteriologists h a v e busied themselves, is milk. A good milk m u s t c o n t a i n a certain a m o u n t of solids and fat, b u t it can be a d u l t e r a t e d w i t h far more h a r m f u l m a t t e r s t h a n water, and these other a d u l t e r a t i o n s are not so readily detected. A few h o u r s a f t e r milking, o r d i n a r y milk has been f o u n d to c o n t a i n I,OOO,OOO g e r m s to the cubic c e n t i m e t e r . H o w d i d these g e t in ? If the u d d e r s of t h e cow are n o t k e p t clean, the first flow of milk will w a s h t h e dirt into the milking-pan. If the m a n who milks the cow is u n c l e a n l y in his habits, u s i n g d i r t y h a n d s in the operation, the m i l k receives this dirt. If t h e stall is the place for milki~ag, a n d o t h e r a n i m a l s are m o v i n g a b o u t , the d u s t raised falls into the open pail and contamina t e s the fluid; and, finally, in t h e t r a n s p o r t a t i o n from the f a r m e r to the collector, from the dealer t o t h e customer, a h u n d r e d o p p o r t u n i t i e s p r e s e n t t h e m s e l v e s for the e n t r a n c e of bacteria, which, w h e n once in, t h r i v e a b u n d a n t l y , the m i l k b e i n g a rich and s u i t a b l e soil for t h e i r growth. In the m a r k e t s of Halle, Berlin a n d Leipsic, R a n k e succeeded in finding, in the milk exposed for sale, considerable
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q u a n t i t i e s of cow-dung, which, of c o u r s e , g r e a t l y increased the n u m b e r of g e r m s to the cubic c e n t i m e t e r - - i n one case up to I69,ooo,ooo. Bolle, the m i l k m a n of Berlin, w h o sells 60,00o q u a r t s of milk daily, has e n d e a v o r e d to m a k e his large e s t a b l i s h m e n t conform to scientific r e q u i r e m e n t s . H e has a c o m p e t e n t bacteriologist, w h o m a k e s f r e q u e n t e x a m i n a t i o n s of the product. T h e milk is o b t a i n e d from such dairies o n l y as are u n d e r his inspection. S e p a r a t e e x a m i n a t i o n s are m a d e of the different herds, so as to trace disease to its proper source. T h e collected milk is filtered each day t h r o u g h i m m e n s e sieves of gravel, which have first been s u b j e c t e d to a high degree of h e a t in order to sterilise them. T h e milk is forced t h r o u g h from b e l o w upwards, and collected in p r o p e r vessels. F o u r t h o u s a n d q u a r t s pass t h r o u g h suc~ a filter in one hour. By this m e a n s t h e dirt is r e m o v e d and with it a b o u t 50 per cent. of the bacteria present. W h i l e this filtered milk keeps longer than the unfiltered, and is m o r e readily sterilised, it is j u s t as d a n g e r o u s if disease g e r m s were originally present, since, as was s t a t e d above, in connection w i t h the filtration of water, the disease g e r m s are j u s t as likely to be a m o n g the 5o per cent. that pass t h r o u g h as to be a m o n g t h o s e t h a t remain. In order to r e n d e r milk c o m p l e t e l y sterile, it m u s t be s u b j e c t e d to such a d e g r e e of h e a t as will c o a g u l a t e the casein and m a k e the p r o d u c t .undesirable in o t h e r ways. If, h o w e v e r , g r e a t care b e exercised in t h e milking, and sterilisation be carried on at once or shortly after, a v e r y m o d e r a t e d e g r e e of heat will be sufficient to m a k e the milk entirely sterile. One of the bacteria t h a t is often f o u n d in milk has v e r y r e s i s t a n t spores, and, therefore, if milk b e c o m e s contamin a t e d b y exposure to the d u s t and dirt of the air or stall, o r d i n a r y w a r m i n g or heating, as is done w h e n milk is P a s t e u r i s e d (so-called sterilised milk), will not suffice to d e s t r o y t h e s e spores. Milk is often sold to us in bottles, a n d one w o u l d i m a g i n e t h a t such a p r o d u c t was r e a s o n a b l y clean ; b u t this b o t t l i n g is done in a v e r y care]ess way, often in the s t r e e t b y s o m e
Nov., ~895.]
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i g n o r a n t delivery boy, while the street sweeper is raising clouds of dust, some of w h i c h lodges in the exposed milk. In one d a i r y in Dresden, G e r m a n y , all the milk comes from stall-fed, or dry-fed, cows, experience h a v i n g shown t h a t such cows give a p r o d u c t t h a t is less variable, and contains fewer germs, and sours less speedily t h a n w h e n t h e y are fed on fresh grass. G r e a t care is t a k e n in the milking, and especial a t t e n t i o n is paid to t h e cleanliness of the employds. A f t e r the milking, t h e m i l k is placed in coolers, w h e r e it r e m a i n s two hours, at a t e m p e r a t u r e of Io°C. T h e n it is p u t into a centrifuge, in order to separate the dirt t h a t m i g h t a c c i d e n t a l l y h a v e fallen in. It is now w a r m e d up to 65 ° C. (Pasteurised), and collected in h a l L p i n t sterilised bottles, a n d t h e filled b o t t l e s a g a i n h e a t e d for one h o u r and three-quarters, at 65 ° C., and quickly cooled. Such milk is r e a s o n a b l y sterile, a n d t h e m e t h o d is t h e only one to be r e c o m m e n d e d . Unless all t h e s e steps are followed the milk c a n n o t be considered sterile. W h a t d a n g e r is t h e r e in m i l k from t u b e r c u l o u s cows ? T h i s is a q u e s t i o n which, j u s t at present, is r e c e i v i n g considable a t t e n t i o n . T u b e r c u l o s i s is v e r y f r e q u e n t a m o n g cattle. In t h e s l a u g h t e r - h o u s e s of Berlin, o u t of i42,ooo h e a d of cattle, 2I,OOO, or i5 per cent., were f o u n d to be tubercular. In all P r u s s i a io per cent. of all t h e cattle s l a u g h t e r e d a n n u a l l y are f o u n d to be affected w i t h this disease. Some v e t e r i n a r i a n s claim t h a t 30 per cent. of all cows are infected, a n d t h a t a h e r d c a n n o t be f o u n d t h a t is e n t i r e l y free from the disease. F r o m this, one can r e a d i l y see the i m p o r t a n c e of this question. In N e w York City 900,000 q~aarts of m i l k are cons u m e d daily. C o n s u m p t i o n is likewise a very c o m m o n disease, c a u s i n g from one-third to one-fourth of all t h e d e a t h s a m o n g adults, a n d m a n y , if n o t t h e g r e a t e r n u m b e r of the diseases of children are t u b e r c u l a r in origin, Is the cow an e n e m y to m a n ? A r e we w a r r a n t e d in a c c u s i n g t h e m i l k of c o n s u m p t i v e cows as b e i n g the cause of c o n s u m p t i o n in m a n ? T h e last word has not y e t been said on this subject. W e can only give the opinions of authori-
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B aH :
[l. F. I.,
ties, the present beliefs g a i n e d from the knowledge at h a n d ; and these are that, if t h e u d d e r s of a cow are unaffected, if there is no local tuberculosis, no bacilli are to be f o u n d in t h e milk, the milk m a y be considered safe. Yet, later i n v e s t i g a t i o n s have shown t h a t the toxic principles of bacteria find t h e i r w a y into the milk, t h a t the milk of an a n i m a l r e n d e r e d i m m u n e to d i p h t h e r i a or t e t a n u s h a s the same properties as the serum of the blood, and can protect o t h e r animals. If this is u n c o n t r o v e r t e d , then the milk of t u b e r c u l o u s or c o n s u m p t i v e cows m a y have w i t h i n it the p r o d u c t s of the tubercle bacilli, and such milk m a y have the same effect upon t h e h u m a n o r g a n i s m as these products o b t a i n e d artificially, or from c u l t u r e s o u t s i d e of the body. T h e discussion on the benefits or ill effects of tuberculin has not y e t been closed, and it is impossible to say, therefore, w h e t h e r such milk, i. e., milk c o n t a i n i n g tuberculin, is posit i v e l y h a r m l e s s or dangerous. In Paris all cows whose milk is offered for sale m u s t be t e s t e d w i t h t u b e r c u l i n to prove t h e i r f r e e d o m from tuberculosis. Our own Board of H e a l t h has s t r o n g t y a d v o c a t e d a similar test. T u b e r c u l i n has been f o u n d reliable in the g r e a t e r n u m ber of cases; i. e., if an a n i m a l s h o w e d signs of t e m p e r a t u r e rise a f t e r the injection of the tuberculin, the disease has always been f o u n d p r e s e n t ; b u t the disease has been f o u n d w h e n no rise has occurred, so t h a t it is a positive test only. T u b e r c u l o s i s is present w h e n e v e r t h e r e is a rise of temperature, b u t it is not necessarily a b s e n t if no reaction occurs. Because tuberculosis is so very frequent, because 2,700 d e a t h s of a d u l t s b e t w e e n 15 and 45 occur every year in this c i t y alone from this one disease, it behooves us to t r y every m e a s u r e t h a t holds out the s l i g h t e s t chance of success in r e d u c i n K this awful mortality, and, therefore, if only as an e x p e r i m e n t , it would be w o r t h the time and m o n e y to d e s t r o y every suspicious animal, and t h u s p r e v e n t the sale of all milk save t h a t o b t a i n e d from p e r f e c t l y s o u n d cows. A n y r e d u c t i o n in the d e a t h rate from this disease will be a step in advance, and our efforts s h o u l d be directed to this end at all cost.
NOV., 1895,]
Recent Adz,ances in Bacteriology.
349
If the milk of c o n s u m p t i v e cows is d a n g e r o u s , t h e n cheese and b u t t e r m a d e f r o m such milk is likewise dangerous, and t h e sale of such s h o u l d be e q u a l l y g u a r d e d against. In G e r m a n y , b u t t e r has been m a d e from sterilised m i l k by the a d d i t i o n of pure c u l t u r e s of certain bacteria, which h a v e the power of c o a g u l a t i n g the milk. Such b u t t e r h a s a c o n s t a n t flavor, a n d does not d e t e r i o r a t e so quickly as b u t t e r p r o d u c e d in t h e o r d i n a r y way. To s u m m a r i s e in r e g a r d to milk, we can say t h a t (x) a careful inspection of the d a i r y ; (2) a close e x a m i n a t i o n of the cattle; and (3) cleanliness in the t r a n s p o r t a t i o n and sale, m u s t be r i g o r o u s l y enforced to s a f e g u a r d the public health. As regards meat, little has been said or done. Meat is r a r e l y used in t h e raw state, and cooking g e n e r a l l y r e n d e r s ineffective the g e r m s likely to be f o u n d present. In the cities of Europe, careful inspection is practiced at t h e abattoirs, and m e a t from diseased cattle is excluded or sold u n d e r restrictions. Meat-shops are likewise kept v e r y clean, and the m e a t is seldom exposed in filthy w a r e h o u s e s . In our own cities some of the m e a t offered for sale on t h e s t a n d s and in s t r e e t shops is m o s t unfit for food~-some of it, indeed, in a state of p u t r e f a c t i o n . Some cities h a v e laws w h i c h m a k e such m e a t liable to seizure, b u t these laws are seldom operative. T h e a d v a n c e s in f e r m e n t a t i o n deserve a t t e n t i o n , for, t h o u g h t h e y are not, s t r i c t l y speaking, connected w i t h our subject, y e t so closely are t h e y e a s t s related to bacteria, and so similar are the m e t h o d s of cultivation, t h a t a n y discoveries in the one field are sure to be of v a l u e in the other. Bacteria h a v e alw_.ays been a d i s t u r b i n g e l e m e n t in industrial f e r m e n t a t i o n s , and expensive m e t h o d s have been resorted to, to p r e v e n t the e n t r a n c e of disease germs---disease, here, m e a n i n g i m p u r e or i m p r o p e r germs. T h e y e a s t s were f o r m e r l y considered as few in n u m b e r - as alcohol-producers and non-alcohol-producers--no serious efforts were m a d e to o b t a i n pure cultures, b u t the m a s h e s a n d brews were kept u n d e r such conditions t h a t the foreign g e r m s were p r e v e n t e d from g r o w i n g or m u l t i p l y i n g . Beer
35 °
Ball.
[J. F. I.,
was stored in ice-cellars, w h i s k e y was s u b j e c t e d to special t e m p e r a t u r e s , and o t h e r e l a b o r a t e m e a s u r e s w e r e used w h i c h now can be d i s p e n s e d with if we s t a r t w i t h p u r e cultures of y e a s t s at the beginning, and avoid the e n t r a n c e of i m p u r i t i e s from air, water, etc. In Denmark, H a n s e n (and from h i m a school has originated) pays g r e a t a t t e n t i o n to the c u l t i v a t i o n of p u r e yeasts. B r e w e r s can obtain from the laboratories such p u r e cultures and t h e r e b y insure a definite alcoholic strength, a c o n s t a n t flavor, and a p r o d u c t t h a t will not deteriorate, even u n d e r v a r y i n g conditions of t e m p e r a t u r e , etc. By e x p e r i m e n t i n g with different c o m b i n a t i o n s of yeasts, v a r i o u s degrees of b i t t e r n e s s and different a r o m a s can be developed. W i n e s d e p e n d v e r y largely for their b o u q u e t , not so m u c h upon the g r a p e as upon the p a r t i c u l a r g e r m or g e r m s used in the f e r m e n t a t i o n of the juice. E x p e r i m e n t e r s have o b t a i n e d , with the s a m e kind of grape, a half-dozen different w i n e s b y using as m a n y different yeasts. As the p i g m e n t yeasts p r o d u c e various colors, so the y e a s t s used in f e r m e n t a t i o n give rise to v a r i o u s ethers, and t h e s e ethers give t h e wine its peculiar b o u q u e t . W e should expect to obtain a R h i n e wine from a N e w J e r s e y g r a p e b y u s i n g the y e a s t s w h i c h are c o m m o n in the R h i n e region, or on t h e R h i n e grape. E v e n o u t of apple most, a good-tasting wine has b e e n p r o d u c e d b y the use of p a r t i c u l a r cultures of yeast. T h e s e researches h a v e r e v o l u t i o n i s e d G e r m a n brewing, and the large b r e w e r i e s now h a v e c o m p e t e n t b a c t e r i o l o g i s t s in their employ, who a t t e n d to t h e cultivation of their yeasts. T h e spaces or holes peculiar to certain cheeses are d u e to the evolution of g a s e s d u r i n g the r i p e n i n g process. T h e s e g a s e s are p r o d u c e d b y certain bacteria, and b y u s i n g pure cultures of these gas-forming bacteria in the m a n u f a c t u r e of cheese, these air.spaces will always occur. T h e odor of cheese is likewise due to bacteria, and special flavors can thus b e o b t a i n e d at will b y u s i n g the particular germs. Bread m a d e from pure y e a s t will be f o u n d to be more
Nov., t895.]
Aluminium Solders.
35 I
digestible, to be l i g h t e r a n d to possess a s w e e t e r flavor. Too little a t t e n t i o n has b e e n paid to this in baking. Mixtures of y e a s t s a n d b a c t e r i a are used, and the b a k i n g p o w d e r or the flour is b l a m e d for poor results. Sour bread is u s u a l l y due to a poor q u a l i t y or i m p u r e kind of yeast. T h e soil out of w h i c h we o b t a i n such i m p o r t a n t food-stuffs has been s t u d i e d b a c t e r i a l l y a n d has been f o u n d to c o n t a i n peculiar germs, which are all n e c e s s a r y to the g r o w t h of the plant. T h e s e are t h e so-called n i t r o g e n - f o r m i n g bacteria. T h e y c o n v e r t the n i t r a t e s into nitrites, the oxidisers of organic material, m o r e necessary to the well-being of vegetable life t h a n a n y t h i n g else. I n s t e a d of u s i n g tons of fertilisers, the a g r i c u l t u r i s t of the f u t u r e will cover his fields w i t h c u l t u r e s of the n i t r o g e n g e r m s a n d o b t a i n b e t t e r results. W e will even h a v e special g e r m s for special plants. T h e science of a g r i c u l t u r e is y e t in its infancy, if we m a y believe the promises held o u t to it b y bacteriology. E v e n at p r e s e n t the a g r i c u l t u r a l colleges are e q u i p p i n g themselves w i t h laboratories for bacteriological research. T h u s I h a v e tried to show t h a t the recent advances in this science are as n o t h i n g c o m p a r e d w i t h w h a t m a y y e t be expected ; t h a t in these germs, microbes and bacteria, mank i n d h a s d e a d l y foes and also i m p o r t a n t friends; t h a t we m u s t do all we can to rid ourselves of the f o r m e r and m a k e the l a t t e r our willing slaves.
ALUMINIUM
SOLDERS.
~
BY JOSEPH RICI-IARDS,
V e r y soon a f t e r Deville first m a d e a l u m i n i u m on a large scale, it was f o u n d t h a t it was a m o s t difficult problem to solder it satisfactorily. T h e o r d i n a r y alloys used for solderi n g were f o u n d n o t to a t t a c h t h e m s e l v e s to a l u m i n i u m , despite every u s u a l precaution, a n d it was seen t h a t unu s u a l solders m u s t be devised to m e e t this u n u s u a l problem. M. Christofle, the g d l d s m i t h , of Paris, gave the s u b j e c t *Abstract of remarks made before t h e Institute.
Ball
."
R E C E N T A D V A N C E S IN B A C T E R I O L O G Y S P E C I A L R E F E R E N C E TO FOOD.*
[ J. F. I..
wrru
BV M. V. ]]ALL, M.D.
T h e lecturer was introduced b y the S e c r e t a r y of the Institute, and spoke as follows : MEMBERS OF THE INSTITUTE, LADIES AND GENTLEMEN: B a c t e r i o l o g y is, comparatively, a r e c e n t science. Only within the last ten y e a r s has it received any special atten. tion, and within this time it has b e e n given a place in t h e medical colleges and b e c o m e r e c o g n i s e d as an i m p o r t a n t d e p a r t m e n t of knowledge. Municipalties are f o r m i n g laboratories for bacteriological work, and g o v e r n m e n t s are instituting, on a large scale, researches, which m u s t e v e n t u a l l y be of g r e a t service to mankind. It is h a r d l y to be expected t h a t this s u b j e c t should as y e t be the c o m m o n p r o p e r t y of a n y b u t those w h o have m a d e it a special study, and, therefore, a few words as to the n a t u r e of bacteria will not be o u t of place here. B a c t e r i a - - f r o m the Greek, m e a n i n g little or m i n u t e rods - - i s a term applied to various forms of organisms, micrcscopic in size, closely allied to the lower t y p e s of fungi and algae ; u s u a l l y c o n t a i n i n g no chlorophyll ; capable, in m a n y instances, of propelling t h e m s e l v e s w i t h swift motion t h r o u g h the liquids in which t h e y are found, and possessing, for this purpose, small cilia or flagella, like o t h e r t y p e s of microscopic plants. T h e y are very minute, r e q u i r i n g for their detection p o w e r f u l lenses. S o m e idea of their size m a y be o b t a i n e d from t h e s t a t e m e n t t h a t in the space of an inch from 15,oo0 to 2o,0oo can be placed side b y side; but, g r o w i n g t o g e t h e r in large n u m b e r s as t h e y do, such a g g r e g a t i o n s or colonies can readily be seen with the u n a i d e d eye, t h o u g h the i n d i v i d u a l m e m b e r s of these colonies cannot be reeognised. *A lecture delivered before the Franklin Institute.
Nov., x895.]
Recelll .dclvances iu Bacteriology.
34 I
Bacteria are n e i t h e r y e a s t s nor moulds, t h o u g h possessing some of the characters of both. T h e name, " b a c t e r i a , " is not a good one, since o t h e r t h a n rod-shaped o r g a n i s m s are collected u n d e r this group. Microeocei are g l o b u l a r or spherical b a c t e r i a ; bacilli are the rod-shaped bacteria ; and spirilli are spiral-formed or t w i s t e d bacteria. T h e colonies of one form are not to be disting u i s h e d from the others, b u t u n d e r t h e microscope the dif_ ferenee in shape is readily m a d e out. Bacteria are quick breeders ; t h e y m u l t i p l y very rapidly. F r o m one or two g e r m s t h o u s a n d s are o b t a i n e d in t h e course of a few hours. Some one has m a d e the calculation t h a t a single germ, if u n i n t e r r u p t e d in its growth, w o u l d fill an ocean with its p r o g e n y in five days ; but, f o r t u n a t e l y , it digs its own g r a v e by the poisons it generates, and so p u t s a l i m i t to its g r o w t h . Some require several days before germin a t i o n occurs. T w o kinds of g r o w t h are k n o w n : one, in which r e p r o d u c t i o n is a process of fission or s e g m e n t a t i o n - - o n e b a c t e r i u m d i v i d i n g itself into two, a n d each of these a g a i n s u b - d i v i d i n g - - i n reality, a c o n t i n u a t i o n r a t h e r t h a n a reproduction. _And a second kind, k n o w n as sporulation. T h e g e r m gives rise to a spore, the spore t h e n takes on a s e p a r a t e existence and, w h e n the conditions favorable to m a t u r a t i o n exist, it gives rise to a n e w germ. Both forms of g r o w t h are utilised by the same b a c t e r i u m . U n d e r o r d i n a r y conditions it m u l t i p l i e s by fission w h e n a p e r m a n e n t form is a d v a n t a g e o u s , or, as some think, w h e n t h e soil is p a r t i c u l a r l y rich, it p r o d u c e s spores. Spores h a v e n o t been f o u n d in all b a c t e r i a ; those possessing t h e m are v e r y r e s i s t a n t to all physical and chemical agencies, and w i t h s t a n d a h i g h degree of h e a t w i t h o u t b e i n g destroyed. F o r the different b a c t e r i a different conditions are neces_ sary. J u s t as different p l a n t s r e q u i r e different kinds of soil a n d t e m p e r a t u r e , so these m i n u t e p l a n t s react differently a n d d e m a n d for t h e i r g r o w t h v a r i o u s s u r r o u n d i n g s . Some are n o t at all particular, a n d flourish on a n y sort of soil. T h e y are like weeds t h a t grow w i t h o u t a t t e n t i o n ; others a g a i n are as sensitive as hot-house plants, and require very carefully p r e p a r e d m e d i a a n d a s u i t a b l y r e g u l a t e d t e m p e r a -
342
Ball:
[J. F. I.,
ture. W h i l e s om e species d e m a n d a p l e n t i f u l s u p p l y of o x y g e n , o t h e r s g r o w o n l y w h e n this is excluded. S u n l i g h t is u s u a l l y d e s t r u c t i v e ; an alkaline m e d i u m is b e t t e r tolerated, t h a n a n e u t r a l one, a n d acids are u s u a l l y h a r m f u l . M o i s t u r e is n e c e s s a r y to g r o w t h . B a c t e r i a are n o t onl y disease-producers, t h e y manuf a c t u r e a h o s t of p r o d u c t s beneficial a n d essential to life. L i fe itself d ep ends , in a g r e a t m e a s u r e , u p o n t h e act i ons of t h e s e m i n u t e plants, w h i c h t r a n s f o r m t h e c o m p l e x molecules into t h e i r e l e m e n t s and m a k e t h e m fit for assimilation. If we could s e p a r a t e t he i n d u s t r i a l g e r m s f r o m t he p a t h o g e n i c or disease-producers, a n d d o m e s t i c a t e t h e former, while we d r i ve t h e l a t t e r out of existence, life w oul d be m o r e w o r t h t he living. T h i s is g r a d u a l l y b e i n g att e m p t e d . S c i e n t i s t s are p o i n t i n g o u t to us t h e p r o p e r t i e s of i n d i v i d u a l v a r i et i es , a nd s h o w i n g us t h e m e t h o d s of cult i v a t i o n ; while h y g i e n i s t s a n d t h e r a p e u t i s t s are d o i n g all t h e y can to e x t e r m i n a t e t he d e s t r o y e r s of life; so t h a t we can a l r e a d y see how, in a few years, c h o l e r a will be a r a r e disease, and t u b e r c u l o s i s will no m o r e be c o u n t e d as t h e c a u s e of one-fifth of all deaths. W h a t advances, if any, h a v e b e e n m a d e in r e c e n t y e a r s as r e l a t e s to t h e s u b j e c t of foods ? T h i s is t h e topic I h a v e b e e n asked to c o n s i d e r : " B a c t e r i a in t h e i r r e l a t i o n to food ?" F i r s t of all, I desire to t a k e up t h e m o s t i m p o r t a n t of foods, n amely , water. W a t e r is a food b e c a u s e it is nece s s a r y to s u s t a i n life, a n d c o n s i d e r e d in this sense air m i g h t also b e classed as a food. B u t w h e t h e r or n o t we call w a t e r a food, t h e r e are o t h e r r e a s o n s sufficient for us to m a k e it a m a t t e r for c o n s i d e r a t i o n here. F o r m e r l y a good w a t e r was one w h i c h c a m e up to a certain chemical standard. T h e a m o u n t of c h l o r i d e s and n i t r a t e s was d e t e r m i n e d , t h e h a r d n e s s was c o m p u t e d and t h e t o t a l a m o u n t of solids a s c e r t a i n e d . If a w a t e r did n o t c o n t a i n m o r e t h a n I g r a i n of c h l o r i n e p e r gallon, it was d e e m e d p o tab le. T o- da y, while c h e m i c a l anal ysi s still has an i m p o r t a n t place in t h e e x a m i n a t i o n of water, it m u s t go h a n d - i n - h a n d w i t h t h e biological or b a c t e r i o l o g i c a l analysis,
Nov., I895.]
Recent ~Jdz,ances in Bacteriology.
343
and we m u s t k n o w w h a t sort of living o r g a n i s m s i n h a b i t or are to be found in t h e specimen in question. In the early days of b a c t e r i o l o g y m u c h stress was laid u p o n the n u m b e r of b a c t e r i a f o u n d in a given q u a n t i t y of water, and w a t e r c o n t a i n i n g m o r e t h a n 5oo colonies to t h e cubic c e n t i m e t e r was d e e m e d unfit for drinking, b u t n o w it is n o t so m u c h the q u a n t i t y as the q u a l i t y of the b a c t e r i a that is looked for. One t y p h o i d bacillus in a gallon of w a t e r is m o r e d a n g e r o u s than one million ordinary w a t e r b a c t e r i a ; in fact, it w o u l d r e n d e r the w a t e r impotable, while the l a t t e r w o u l d be harmless. T h u s , the w a t e r a n a l y s t of to-day m u s t be a c o m p e t e n t b a c t e r i o l o g i s t as well as c h e m i s t ; and to b e a b a c t e r i o l o g i s t m e a n s a p a t h o l o g i s t as well, for, in the i n v e s t i g a t i o n of bacteria, animals m u s t be u s e d for experiment, and t h e n a t u r e of the diseases caused b y t h e b a c t e r i a m u s t b e k n o w n to the experimenter. As in t h e earlier chemical analyses, t h e chlorine itself w a s not considered d a n g e r o u s , b u t simply one of the indications of faecal c o n t a m i n a t i o n , so in the bacterial examination, t h e presence of certain h a r m l e s s g e r m s m a y indicate d a n g e r o u s c o n t a m i n a t i o n s . F o r instance, the presence of t h e bacilli c o m m o n l y f o u n d in h u m a n faeces, w h i c h in themselves are non-pathogenic, would, of course, lead one to infer t h a t h u m a n s e w a g e h a d b e c o m e m i x e d with the w a t e r supply. T h e m e t h o d s for t h e d e t e c t i o n of t y p h o i d bacilli in drinking-water leave m u c h to b e desired. T h e e x a m i n a t i o n is often u n d e r t a k e n too late, w h e n the bacilli are no longer present,or h a v e b e e n d e s t r o y e d b y the ordinary w a t e r bacteria. T y p h o i d bacilli do n o t live l o n g in ordinary drinking-water; and yet, if t h e w a t e r be c o n t a m i n a t e d with them, a w h o l e city or d i s t r i c t can b e c o m e i n f e c t e d in a s h o r t time, and w h e n suspicion is directed to the w a t e r the g e r m s have disappeared. T o . a less degree, this is likewise true of t h e cholera spirillum, w h i c h acts so q u i c k l y and is so deadly, a n d w h i c h u s u a l l y is spread t h r o u g h t h e drinking-water. A m e t h o d lately described, and w h i c h p r o m i s e s success, is to take a large q u a n t i t y of t h e s u s p e c t e d w a t e r (200 cubic centimeters), and add to it 2 g r a m s of p e p t o n e and 2 g r a m s of
344
BaH :
[J. ~. 1.,
chloride of sodium. Place this in the i n c u b a t i n g oven, and, if cholera g e r m s are present, t h e y will m u l t i p l y rapidly, so t h a t t h e y can readily be d e t e c t e d in the course of ten to twelve hours. Bacteric e x a m i n a t i o n s have been m o s t useful in the testing of water filters, " g e r m - p r o o f " filters, etc. Several filters are now in the market, which claim to be germ-proof ; t h a t is to say, which are supposed to p r e v e n t the passage of bacteria t h r o u g h the very m i n u t e pores of the filter. T h e s e filters are made of baked clay, infusorial earth, porcelain, etc. As a rule, t h e y can deliver a g e r m l e s s w a t e r only for a few d a y s in succession, when, o w i n g to the a c t i v i t y of the b a c t e r i a which have collected on the surface of the filter Cylinder, the pores are p e n e t r a t e d by the g r o w t h , and more b a c t e r i a t h a n usual find t h e i r w a y into the water. This, in some cases, can be p r e v e n t e d by a careful cleansing, every few days, of the filter tube. All t u b e s are not alike, and some afford no protection at all, t h o u g h t h e y clarify the w a t e r by k e e p i n g out the grosser particles of dirt. Filters are best tested by a d d i n g to the water, before filtration, some well-known b a c t e r i u m (usually the red pigm e n t - f o r m i n g and r a p i d - g r o w i n g Bacillus prodiKiosus ) m a k i n g c u l t u r e s before and t h e n after filtration. If, u n d e r suitable precautions, the g e r m is f o u n d p r e s e n t in the filtered water, t h e filter is imperfect. In the t e s t i n g of large filtering plants, where it is not e x p e c t e d t h a t t h e w a t e r will be perfectly free from germs, q u a n t i t a t i v e m e t h o d s m u s t be used, in order to tell w h a t p e r c e n t a g e of b a c t e r i a is left behind. T h e s e large filtering p l a n t s are in use in several cities, and, it seems to me, t h e y are of d o u b t f u l value only. It is true, the w a t e r is more p l e a s i n g to the eye, and, for toilet a n d l a u n d r y purposes, more v a l u a b l e ; b u t if the w a t e r is c o n t a m i n a t e d w i t h disease g e r m s there is no s u r e t y t h a t t h e y will be a m o n g the 50 per cent. filtered out. T h e y are j u s t as liable to pass t h r o u g h as the others, and such a w a t e r is not safe. F r o m the s a n i t a r y p o i n t of view, filtering plants are only v a l u a b l e w h e n the w a t e r is u n c o n t a m i n a t e d by h u m a n s e w a g e ; a n d to erect such a p l a n t in our city, w i t h o u t p a y i n g a n y a t t e n t i o n to the s o u r c e of our w a t e r
Nov.. t895.]
Recent Advalzces in BacterioloEy.
345
supply, and even allowing it to be p o l l u t e d along its whole course, will h a r d l y reduce the d e a t h rate, t h o u g h it m a y add to the aesthetic q u a l i t y of the water. On an average, 5oo d e a t h s occur every year in this city from t y p h o i d fever. T h i s m e a n s at least 6,ooo cases. F r o m an economic point of view, t h e persons affected are the most valuable m e m b e r s of society, chiefly y o u n g adults b e t w e e n the ages of 2o and 4o. T h e expense, in loss of time, medical a t t e n d a n c e , etc., is at least $ioo for each case, a total cost of $6oo,ooo y e a r l y from this one disease, to say n o t h i n g a b o u t the loss of life; and all because we are obliged to d r i n k the s e w a g e of half a dozen t o w n s above us, a n d the d r a i n i n g s from g r a v e y a r d s and pigsties along the banks of the Schuylkill. A n d while we are t h u s t r e a t e d by the cities above us, we s e n d our sewage to the t o w n s below. Some strict m e a s u r e s m u s t be p u t into practice, w h i c h will p r e v e n t this p o l l u t i o n of our drinking-water. T h e second i m p o r t a n t article of food, with w h i c h bacteriologists h a v e busied themselves, is milk. A good milk m u s t c o n t a i n a certain a m o u n t of solids and fat, b u t it can be a d u l t e r a t e d w i t h far more h a r m f u l m a t t e r s t h a n water, and these other a d u l t e r a t i o n s are not so readily detected. A few h o u r s a f t e r milking, o r d i n a r y milk has been f o u n d to c o n t a i n I,OOO,OOO g e r m s to the cubic c e n t i m e t e r . H o w d i d these g e t in ? If the u d d e r s of t h e cow are n o t k e p t clean, the first flow of milk will w a s h t h e dirt into the milking-pan. If the m a n who milks the cow is u n c l e a n l y in his habits, u s i n g d i r t y h a n d s in the operation, the m i l k receives this dirt. If t h e stall is the place for milki~ag, a n d o t h e r a n i m a l s are m o v i n g a b o u t , the d u s t raised falls into the open pail and contamina t e s the fluid; and, finally, in t h e t r a n s p o r t a t i o n from the f a r m e r to the collector, from the dealer t o t h e customer, a h u n d r e d o p p o r t u n i t i e s p r e s e n t t h e m s e l v e s for the e n t r a n c e of bacteria, which, w h e n once in, t h r i v e a b u n d a n t l y , the m i l k b e i n g a rich and s u i t a b l e soil for t h e i r growth. In the m a r k e t s of Halle, Berlin a n d Leipsic, R a n k e succeeded in finding, in the milk exposed for sale, considerable
346
Ball:
[J. F. I.,
q u a n t i t i e s of cow-dung, which, of c o u r s e , g r e a t l y increased the n u m b e r of g e r m s to the cubic c e n t i m e t e r - - i n one case up to I69,ooo,ooo. Bolle, the m i l k m a n of Berlin, w h o sells 60,00o q u a r t s of milk daily, has e n d e a v o r e d to m a k e his large e s t a b l i s h m e n t conform to scientific r e q u i r e m e n t s . H e has a c o m p e t e n t bacteriologist, w h o m a k e s f r e q u e n t e x a m i n a t i o n s of the product. T h e milk is o b t a i n e d from such dairies o n l y as are u n d e r his inspection. S e p a r a t e e x a m i n a t i o n s are m a d e of the different herds, so as to trace disease to its proper source. T h e collected milk is filtered each day t h r o u g h i m m e n s e sieves of gravel, which have first been s u b j e c t e d to a high degree of h e a t in order to sterilise them. T h e milk is forced t h r o u g h from b e l o w upwards, and collected in p r o p e r vessels. F o u r t h o u s a n d q u a r t s pass t h r o u g h suc~ a filter in one hour. By this m e a n s t h e dirt is r e m o v e d and with it a b o u t 50 per cent. of the bacteria present. W h i l e this filtered milk keeps longer than the unfiltered, and is m o r e readily sterilised, it is j u s t as d a n g e r o u s if disease g e r m s were originally present, since, as was s t a t e d above, in connection w i t h the filtration of water, the disease g e r m s are j u s t as likely to be a m o n g the 5o per cent. that pass t h r o u g h as to be a m o n g t h o s e t h a t remain. In order to r e n d e r milk c o m p l e t e l y sterile, it m u s t be s u b j e c t e d to such a d e g r e e of h e a t as will c o a g u l a t e the casein and m a k e the p r o d u c t .undesirable in o t h e r ways. If, h o w e v e r , g r e a t care b e exercised in t h e milking, and sterilisation be carried on at once or shortly after, a v e r y m o d e r a t e d e g r e e of heat will be sufficient to m a k e the milk entirely sterile. One of the bacteria t h a t is often f o u n d in milk has v e r y r e s i s t a n t spores, and, therefore, if milk b e c o m e s contamin a t e d b y exposure to the d u s t and dirt of the air or stall, o r d i n a r y w a r m i n g or heating, as is done w h e n milk is P a s t e u r i s e d (so-called sterilised milk), will not suffice to d e s t r o y t h e s e spores. Milk is often sold to us in bottles, a n d one w o u l d i m a g i n e t h a t such a p r o d u c t was r e a s o n a b l y clean ; b u t this b o t t l i n g is done in a v e r y care]ess way, often in the s t r e e t b y s o m e
Nov., ~895.]
Recent Advances in Bacteriology.
347
i g n o r a n t delivery boy, while the street sweeper is raising clouds of dust, some of w h i c h lodges in the exposed milk. In one d a i r y in Dresden, G e r m a n y , all the milk comes from stall-fed, or dry-fed, cows, experience h a v i n g shown t h a t such cows give a p r o d u c t t h a t is less variable, and contains fewer germs, and sours less speedily t h a n w h e n t h e y are fed on fresh grass. G r e a t care is t a k e n in the milking, and especial a t t e n t i o n is paid to t h e cleanliness of the employds. A f t e r the milking, t h e m i l k is placed in coolers, w h e r e it r e m a i n s two hours, at a t e m p e r a t u r e of Io°C. T h e n it is p u t into a centrifuge, in order to separate the dirt t h a t m i g h t a c c i d e n t a l l y h a v e fallen in. It is now w a r m e d up to 65 ° C. (Pasteurised), and collected in h a l L p i n t sterilised bottles, a n d t h e filled b o t t l e s a g a i n h e a t e d for one h o u r and three-quarters, at 65 ° C., and quickly cooled. Such milk is r e a s o n a b l y sterile, a n d t h e m e t h o d is t h e only one to be r e c o m m e n d e d . Unless all t h e s e steps are followed the milk c a n n o t be considered sterile. W h a t d a n g e r is t h e r e in m i l k from t u b e r c u l o u s cows ? T h i s is a q u e s t i o n which, j u s t at present, is r e c e i v i n g considable a t t e n t i o n . T u b e r c u l o s i s is v e r y f r e q u e n t a m o n g cattle. In t h e s l a u g h t e r - h o u s e s of Berlin, o u t of i42,ooo h e a d of cattle, 2I,OOO, or i5 per cent., were f o u n d to be tubercular. In all P r u s s i a io per cent. of all t h e cattle s l a u g h t e r e d a n n u a l l y are f o u n d to be affected w i t h this disease. Some v e t e r i n a r i a n s claim t h a t 30 per cent. of all cows are infected, a n d t h a t a h e r d c a n n o t be f o u n d t h a t is e n t i r e l y free from the disease. F r o m this, one can r e a d i l y see the i m p o r t a n c e of this question. In N e w York City 900,000 q~aarts of m i l k are cons u m e d daily. C o n s u m p t i o n is likewise a very c o m m o n disease, c a u s i n g from one-third to one-fourth of all t h e d e a t h s a m o n g adults, a n d m a n y , if n o t t h e g r e a t e r n u m b e r of the diseases of children are t u b e r c u l a r in origin, Is the cow an e n e m y to m a n ? A r e we w a r r a n t e d in a c c u s i n g t h e m i l k of c o n s u m p t i v e cows as b e i n g the cause of c o n s u m p t i o n in m a n ? T h e last word has not y e t been said on this subject. W e can only give the opinions of authori-
348
B aH :
[l. F. I.,
ties, the present beliefs g a i n e d from the knowledge at h a n d ; and these are that, if t h e u d d e r s of a cow are unaffected, if there is no local tuberculosis, no bacilli are to be f o u n d in t h e milk, the milk m a y be considered safe. Yet, later i n v e s t i g a t i o n s have shown t h a t the toxic principles of bacteria find t h e i r w a y into the milk, t h a t the milk of an a n i m a l r e n d e r e d i m m u n e to d i p h t h e r i a or t e t a n u s h a s the same properties as the serum of the blood, and can protect o t h e r animals. If this is u n c o n t r o v e r t e d , then the milk of t u b e r c u l o u s or c o n s u m p t i v e cows m a y have w i t h i n it the p r o d u c t s of the tubercle bacilli, and such milk m a y have the same effect upon t h e h u m a n o r g a n i s m as these products o b t a i n e d artificially, or from c u l t u r e s o u t s i d e of the body. T h e discussion on the benefits or ill effects of tuberculin has not y e t been closed, and it is impossible to say, therefore, w h e t h e r such milk, i. e., milk c o n t a i n i n g tuberculin, is posit i v e l y h a r m l e s s or dangerous. In Paris all cows whose milk is offered for sale m u s t be t e s t e d w i t h t u b e r c u l i n to prove t h e i r f r e e d o m from tuberculosis. Our own Board of H e a l t h has s t r o n g t y a d v o c a t e d a similar test. T u b e r c u l i n has been f o u n d reliable in the g r e a t e r n u m ber of cases; i. e., if an a n i m a l s h o w e d signs of t e m p e r a t u r e rise a f t e r the injection of the tuberculin, the disease has always been f o u n d p r e s e n t ; b u t the disease has been f o u n d w h e n no rise has occurred, so t h a t it is a positive test only. T u b e r c u l o s i s is present w h e n e v e r t h e r e is a rise of temperature, b u t it is not necessarily a b s e n t if no reaction occurs. Because tuberculosis is so very frequent, because 2,700 d e a t h s of a d u l t s b e t w e e n 15 and 45 occur every year in this c i t y alone from this one disease, it behooves us to t r y every m e a s u r e t h a t holds out the s l i g h t e s t chance of success in r e d u c i n K this awful mortality, and, therefore, if only as an e x p e r i m e n t , it would be w o r t h the time and m o n e y to d e s t r o y every suspicious animal, and t h u s p r e v e n t the sale of all milk save t h a t o b t a i n e d from p e r f e c t l y s o u n d cows. A n y r e d u c t i o n in the d e a t h rate from this disease will be a step in advance, and our efforts s h o u l d be directed to this end at all cost.
NOV., 1895,]
Recent Adz,ances in Bacteriology.
349
If the milk of c o n s u m p t i v e cows is d a n g e r o u s , t h e n cheese and b u t t e r m a d e f r o m such milk is likewise dangerous, and t h e sale of such s h o u l d be e q u a l l y g u a r d e d against. In G e r m a n y , b u t t e r has been m a d e from sterilised m i l k by the a d d i t i o n of pure c u l t u r e s of certain bacteria, which h a v e the power of c o a g u l a t i n g the milk. Such b u t t e r h a s a c o n s t a n t flavor, a n d does not d e t e r i o r a t e so quickly as b u t t e r p r o d u c e d in t h e o r d i n a r y way. To s u m m a r i s e in r e g a r d to milk, we can say t h a t (x) a careful inspection of the d a i r y ; (2) a close e x a m i n a t i o n of the cattle; and (3) cleanliness in the t r a n s p o r t a t i o n and sale, m u s t be r i g o r o u s l y enforced to s a f e g u a r d the public health. As regards meat, little has been said or done. Meat is r a r e l y used in t h e raw state, and cooking g e n e r a l l y r e n d e r s ineffective the g e r m s likely to be f o u n d present. In the cities of Europe, careful inspection is practiced at t h e abattoirs, and m e a t from diseased cattle is excluded or sold u n d e r restrictions. Meat-shops are likewise kept v e r y clean, and the m e a t is seldom exposed in filthy w a r e h o u s e s . In our own cities some of the m e a t offered for sale on t h e s t a n d s and in s t r e e t shops is m o s t unfit for food~-some of it, indeed, in a state of p u t r e f a c t i o n . Some cities h a v e laws w h i c h m a k e such m e a t liable to seizure, b u t these laws are seldom operative. T h e a d v a n c e s in f e r m e n t a t i o n deserve a t t e n t i o n , for, t h o u g h t h e y are not, s t r i c t l y speaking, connected w i t h our subject, y e t so closely are t h e y e a s t s related to bacteria, and so similar are the m e t h o d s of cultivation, t h a t a n y discoveries in the one field are sure to be of v a l u e in the other. Bacteria h a v e alw_.ays been a d i s t u r b i n g e l e m e n t in industrial f e r m e n t a t i o n s , and expensive m e t h o d s have been resorted to, to p r e v e n t the e n t r a n c e of disease germs---disease, here, m e a n i n g i m p u r e or i m p r o p e r germs. T h e y e a s t s were f o r m e r l y considered as few in n u m b e r - as alcohol-producers and non-alcohol-producers--no serious efforts were m a d e to o b t a i n pure cultures, b u t the m a s h e s a n d brews were kept u n d e r such conditions t h a t the foreign g e r m s were p r e v e n t e d from g r o w i n g or m u l t i p l y i n g . Beer
35 °
Ball.
[J. F. I.,
was stored in ice-cellars, w h i s k e y was s u b j e c t e d to special t e m p e r a t u r e s , and o t h e r e l a b o r a t e m e a s u r e s w e r e used w h i c h now can be d i s p e n s e d with if we s t a r t w i t h p u r e cultures of y e a s t s at the beginning, and avoid the e n t r a n c e of i m p u r i t i e s from air, water, etc. In Denmark, H a n s e n (and from h i m a school has originated) pays g r e a t a t t e n t i o n to the c u l t i v a t i o n of p u r e yeasts. B r e w e r s can obtain from the laboratories such p u r e cultures and t h e r e b y insure a definite alcoholic strength, a c o n s t a n t flavor, and a p r o d u c t t h a t will not deteriorate, even u n d e r v a r y i n g conditions of t e m p e r a t u r e , etc. By e x p e r i m e n t i n g with different c o m b i n a t i o n s of yeasts, v a r i o u s degrees of b i t t e r n e s s and different a r o m a s can be developed. W i n e s d e p e n d v e r y largely for their b o u q u e t , not so m u c h upon the g r a p e as upon the p a r t i c u l a r g e r m or g e r m s used in the f e r m e n t a t i o n of the juice. E x p e r i m e n t e r s have o b t a i n e d , with the s a m e kind of grape, a half-dozen different w i n e s b y using as m a n y different yeasts. As the p i g m e n t yeasts p r o d u c e various colors, so the y e a s t s used in f e r m e n t a t i o n give rise to v a r i o u s ethers, and t h e s e ethers give t h e wine its peculiar b o u q u e t . W e should expect to obtain a R h i n e wine from a N e w J e r s e y g r a p e b y u s i n g the y e a s t s w h i c h are c o m m o n in the R h i n e region, or on t h e R h i n e grape. E v e n o u t of apple most, a good-tasting wine has b e e n p r o d u c e d b y the use of p a r t i c u l a r cultures of yeast. T h e s e researches h a v e r e v o l u t i o n i s e d G e r m a n brewing, and the large b r e w e r i e s now h a v e c o m p e t e n t b a c t e r i o l o g i s t s in their employ, who a t t e n d to t h e cultivation of their yeasts. T h e spaces or holes peculiar to certain cheeses are d u e to the evolution of g a s e s d u r i n g the r i p e n i n g process. T h e s e g a s e s are p r o d u c e d b y certain bacteria, and b y u s i n g pure cultures of these gas-forming bacteria in the m a n u f a c t u r e of cheese, these air.spaces will always occur. T h e odor of cheese is likewise due to bacteria, and special flavors can thus b e o b t a i n e d at will b y u s i n g the particular germs. Bread m a d e from pure y e a s t will be f o u n d to be more
Nov., t895.]
Aluminium Solders.
35 I
digestible, to be l i g h t e r a n d to possess a s w e e t e r flavor. Too little a t t e n t i o n has b e e n paid to this in baking. Mixtures of y e a s t s a n d b a c t e r i a are used, and the b a k i n g p o w d e r or the flour is b l a m e d for poor results. Sour bread is u s u a l l y due to a poor q u a l i t y or i m p u r e kind of yeast. T h e soil out of w h i c h we o b t a i n such i m p o r t a n t food-stuffs has been s t u d i e d b a c t e r i a l l y a n d has been f o u n d to c o n t a i n peculiar germs, which are all n e c e s s a r y to the g r o w t h of the plant. T h e s e are t h e so-called n i t r o g e n - f o r m i n g bacteria. T h e y c o n v e r t the n i t r a t e s into nitrites, the oxidisers of organic material, m o r e necessary to the well-being of vegetable life t h a n a n y t h i n g else. I n s t e a d of u s i n g tons of fertilisers, the a g r i c u l t u r i s t of the f u t u r e will cover his fields w i t h c u l t u r e s of the n i t r o g e n g e r m s a n d o b t a i n b e t t e r results. W e will even h a v e special g e r m s for special plants. T h e science of a g r i c u l t u r e is y e t in its infancy, if we m a y believe the promises held o u t to it b y bacteriology. E v e n at p r e s e n t the a g r i c u l t u r a l colleges are e q u i p p i n g themselves w i t h laboratories for bacteriological research. T h u s I h a v e tried to show t h a t the recent advances in this science are as n o t h i n g c o m p a r e d w i t h w h a t m a y y e t be expected ; t h a t in these germs, microbes and bacteria, mank i n d h a s d e a d l y foes and also i m p o r t a n t friends; t h a t we m u s t do all we can to rid ourselves of the f o r m e r and m a k e the l a t t e r our willing slaves.
ALUMINIUM
SOLDERS.
~
BY JOSEPH RICI-IARDS,
V e r y soon a f t e r Deville first m a d e a l u m i n i u m on a large scale, it was f o u n d t h a t it was a m o s t difficult problem to solder it satisfactorily. T h e o r d i n a r y alloys used for solderi n g were f o u n d n o t to a t t a c h t h e m s e l v e s to a l u m i n i u m , despite every u s u a l precaution, a n d it was seen t h a t unu s u a l solders m u s t be devised to m e e t this u n u s u a l problem. M. Christofle, the g d l d s m i t h , of Paris, gave the s u b j e c t *Abstract of remarks made before t h e Institute.