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Bacteriology of Milk
February, 1904]
RCVlCWS Kind of preservative.
Salicylic acid (added just before feeding) Boric acid (added just before feeding) Formaldehyde (added just before feeding) Boric acid (added 24 hours before feeding) Borax (added 24 hours before feeding) Fonnaldehyde (added 24 hours before feeding) Salicylic acid (added 24 hours before feeding) No preservative
307 I Proteid.
i Per ce~t. 98-0'2 93"84 95"01 91"00 92"22 94 "83 90"04 93 "52
Fat.
9306 97"16 97"75 97 "57 97"35 98"36 92'81 97'37
" In all of the series tile comparative results were nearly the same, and the results in the two seasons' work were so nearly the same that, it would appear t h a t the work was exhaustive, and could be depended upon to represent fairly well the results that would be obtained if this same line of work was carried on indefinitely. " From the results of this work many people may be inclined to think t h a t milk preserved with formaldehyde is even to be preferred to milk treated with no preservative, as the tables evidently show it to be more digestible. . But it would be entirely possible for the preservative to render the milk more digestible and still have properties that would prove injurious. I t is entirely possible for the preservative to unduly stimulate the digestive organs and in the course of time bring them to a diseased condition. For this reason it is impossible to say that formaldehyde, if injurious, is the least injurious of any of the preservatives used in the milk business. The fact t h a t the other preservatives used made ~he milk less digestible is sufficient to condemn them. Adults could possibly drink such milk with impunity, but in the tenement districts of cities, where the babies h a v e a hard struggle fol existence, it takes a very little to turn the scMe either in favour or against their chances for life." The average gain in weight per calf during the three-day periods in which milk with boric acid was fed was 0"5 lb., milk with salicylic acid 3 lb., with formaldehyde 5 lb., and milk with no preservative 1 lb. " The calves fed for an extended period with milk preserved with boric acid and formMdehyde made very satisfactory gains in weight. The two receiving the boric acid lost a good share of their hair, presumably from the effects of the acid."
REVIEWS. BXCTERIOLOOY OF MILK. By Harold Swithinbank, of the Bacteriological Research Laboratory, Denham, and George Newman, ~l t~. F.R.S.E., D.P.H., Medical Officer of Health of Finsbury, With Special Chapters, also by Dr. Newman, on the Spread of Disease by Milk and.the Control of the Milk Supply. Pp. 609 and ix. Price 25s. London : J o h n Murray. The authors are to be congratulated on the production, after five years' labour, of what is likely to be for a very long time the standard book on milk. Various chapters deal with the chemistry, physiology, and pathology of milk; with bacteriological technique; the bacterioscopie examination of air, water, and milk; milk fermentation; economic bacteria in milk; pathogenic bacteria in milk; milk-borne disease;
308
Reviews
[Public Health
the flora of milk, and the control of the milk supply ; while in a copious appendix are discussed various cognate matters of interest, ranging from glass-blowing to infant milk depdts. So manifold indeed are the problems raised by the writers that it is hardly possible within the limits of a review to give more than the general impression which we have formed on reading the book. In the first place Chapter I (General Conditions affecting Bacteria in Milk) appears the least satisfactory ; in places it appears to lack the perspicuity which is generally characteristic of the writers. For instance, on page 6, 45 to 50 per cent of fat is said to be found in " norms1 cream," while on page 8 cream is stated to contain only about 27 per cent of fat. Probably " normal cream" means cream of the quality which modern separators are generally set to produce, while the latter figure from KSnig is the average of several specimens prepared from hand-skimmed milk. Again, on page 10, Cautley is quoted as stating that " boiling milk does not materially affect its power of clotting in the stomach," whereas in the second edition of " The Feeding of Infants " Cautley agrees with the statement on page 11 that " m i l k which has been raised to the boiling point is resistant to the action of rennet." Both these points are naturally of minor importance, but they happened to be matters in regard to which the reviewer was seeking for information. Other slight ambiguities can also be found in this chapter, but one must refrain from carping at a work of such great general excellenee. With regard to a bacterioseopic standard for milk, the writers admit the reasonableness of the figures adopted for certified milk in America. They point out, however, that such standards are not all-sufficient. Just as in the case of water, the kind of bacteria present and the whole past history of the milk must be reviewed before an absolute opinion could be given as to its suitability for food. Though this is perfectly true, it seems not untikely . . . that . bacterioscopic examination may prove as. useful for milk as similar examinations have proved for water, and that lust as an abnormal bacterial count in a well-water may put the medical officer on the q u i r i v e for surface contamination, so any great departure from the bacterioscopic standard for milk is a useful indicator of the milk having been improperly treated at some stage of its past history. Very interesting are the results given on p. 130 et sea]. of the writer's investigations of the bacterial content of milk, kept at various temperatures for varying periods. Though the results vary in each instance, there is at all temperatures a sudden rise in the number of bacteria, a sudden fall, a steady rise to a maximum, followed by a steady fall to ultimate sterility. The first rise is believed to be due to the development of various extraneous organisms, while the second tide is mainly due to the growth of lactic acid organisms. Many popular fallacies are exposed by the authors, notably the theory that the centrifugalization of milk will remove the bacteria. That this is a fallacy was sufficiently proved by the Bedford epidemic of 1902. In this case the milk was passed through a separator " to filter milk, removing tubercle and other disease germs." As a matter of fact, separated milk contains 25 per cent of the original organisms. The much-debated topic of bovine tuberculosis is naturally discussed at length. Pending the report of the present Royal Commission the writers have adopted the provisional attitude " t h a t tuberculosis in all animals is generically one and the same disease, but that it differs in various ways in different animals, and according to the strain and virulence of the infecting bacillus." They also hold that human and
February, 19041
Reviews
309
bovine tuberculosis a r e intercommunicable, but that " cross-infection is probably less common than is generally supposed." On the other hand, they distinctly point out that in their opinion tuberculous milk " i s being sold, not alone to the prejudice, but also to the risk, of the purchaser." It will be seen that this vexed question has been treated judicially, and indeed the whole chapter, which was written by Dr. Newman, merits careful study by those responsible for the control of milk and meat. In subsequent chapters milk-borne scarlatina, typhoid, and diphtheria are fully discussed, while a section on methods of enquiry into milk-borne disease is full of interest, though perhaps somewhat beyond the scope of the book. Lastly, Dr. Newman discusses the control of the milk supply by the State, by private enterprise, and by the trade, and ends with a summary of recommendations. These are in the main identical with those made by him to the Finsbury Council, and printed in the present issue o~ P u b l i c H e a l t h , * so need n o t be repeated here. Perhaps some regret will be felt that the authors have not seen their way to suggest new methods of controlling the milk trade. I t should, however, be remembered that short cuts are rarely practicable in Public Health work, and that true preventive work usually resolves itself into the old problems of removing filth and dispelling ignorance. In conclusion, we can only add that while this work is German in its thoroughness, it has one feature that is essentially British, namely, it does not emanate from a State department or richly endowed University, but from the private laboratory of one of the authors, who have by years of strenuous work rendered valuable service to the State and the Public Health Service. The book is superbly got up and illustrated with chromo lithographs, Woodburytype reproductions of photographs of cultures, and numerous blocks very beautifully executed and reproduced.
DIAGRAMS FOR THE USE OF CLASSES OF TECHNICAL INSTRUCTION FOR PLUMBERS. Price ls., 8~ in. by 5~ in., 26 pp. London: The Worshipful Company of Plumbers. The diagrams, about ~rth full size, are the first of a series intended to illustrate some of the more important scientific principles underlying the operations of the plumber ; types of apparatus ; the principles of their construction; and the workmanship employed in fitting them. The diagrams and accompanying descriptions comprise: Bends, corbel and washdown w.c.'s, hydrostatics, lead work, levers applied to ball valves, overflows and wastes, soil pipe joints, specific gravity, siphons, trap showing water seal, valve closet, ventilated sink waste and gutley. The diagrams are admirably executed, and will be of value not only to plumbers, but to those engaged in both the practice and study of sanitation. Fullsize diagrams (53 in. by 31 in.) are also obtainable for teaching purposes. Either set might be kept in the offices of local authorities for the benefit of builders, plumbers, and others. * See pages 254-290.
RCVlCWS Kind of preservative.
Salicylic acid (added just before feeding) Boric acid (added just before feeding) Formaldehyde (added just before feeding) Boric acid (added 24 hours before feeding) Borax (added 24 hours before feeding) Fonnaldehyde (added 24 hours before feeding) Salicylic acid (added 24 hours before feeding) No preservative
307 I Proteid.
i Per ce~t. 98-0'2 93"84 95"01 91"00 92"22 94 "83 90"04 93 "52
Fat.
9306 97"16 97"75 97 "57 97"35 98"36 92'81 97'37
" In all of the series tile comparative results were nearly the same, and the results in the two seasons' work were so nearly the same that, it would appear t h a t the work was exhaustive, and could be depended upon to represent fairly well the results that would be obtained if this same line of work was carried on indefinitely. " From the results of this work many people may be inclined to think t h a t milk preserved with formaldehyde is even to be preferred to milk treated with no preservative, as the tables evidently show it to be more digestible. . But it would be entirely possible for the preservative to render the milk more digestible and still have properties that would prove injurious. I t is entirely possible for the preservative to unduly stimulate the digestive organs and in the course of time bring them to a diseased condition. For this reason it is impossible to say that formaldehyde, if injurious, is the least injurious of any of the preservatives used in the milk business. The fact t h a t the other preservatives used made ~he milk less digestible is sufficient to condemn them. Adults could possibly drink such milk with impunity, but in the tenement districts of cities, where the babies h a v e a hard struggle fol existence, it takes a very little to turn the scMe either in favour or against their chances for life." The average gain in weight per calf during the three-day periods in which milk with boric acid was fed was 0"5 lb., milk with salicylic acid 3 lb., with formaldehyde 5 lb., and milk with no preservative 1 lb. " The calves fed for an extended period with milk preserved with boric acid and formMdehyde made very satisfactory gains in weight. The two receiving the boric acid lost a good share of their hair, presumably from the effects of the acid."
REVIEWS. BXCTERIOLOOY OF MILK. By Harold Swithinbank, of the Bacteriological Research Laboratory, Denham, and George Newman, ~l t~. F.R.S.E., D.P.H., Medical Officer of Health of Finsbury, With Special Chapters, also by Dr. Newman, on the Spread of Disease by Milk and.the Control of the Milk Supply. Pp. 609 and ix. Price 25s. London : J o h n Murray. The authors are to be congratulated on the production, after five years' labour, of what is likely to be for a very long time the standard book on milk. Various chapters deal with the chemistry, physiology, and pathology of milk; with bacteriological technique; the bacterioscopie examination of air, water, and milk; milk fermentation; economic bacteria in milk; pathogenic bacteria in milk; milk-borne disease;
308
Reviews
[Public Health
the flora of milk, and the control of the milk supply ; while in a copious appendix are discussed various cognate matters of interest, ranging from glass-blowing to infant milk depdts. So manifold indeed are the problems raised by the writers that it is hardly possible within the limits of a review to give more than the general impression which we have formed on reading the book. In the first place Chapter I (General Conditions affecting Bacteria in Milk) appears the least satisfactory ; in places it appears to lack the perspicuity which is generally characteristic of the writers. For instance, on page 6, 45 to 50 per cent of fat is said to be found in " norms1 cream," while on page 8 cream is stated to contain only about 27 per cent of fat. Probably " normal cream" means cream of the quality which modern separators are generally set to produce, while the latter figure from KSnig is the average of several specimens prepared from hand-skimmed milk. Again, on page 10, Cautley is quoted as stating that " boiling milk does not materially affect its power of clotting in the stomach," whereas in the second edition of " The Feeding of Infants " Cautley agrees with the statement on page 11 that " m i l k which has been raised to the boiling point is resistant to the action of rennet." Both these points are naturally of minor importance, but they happened to be matters in regard to which the reviewer was seeking for information. Other slight ambiguities can also be found in this chapter, but one must refrain from carping at a work of such great general excellenee. With regard to a bacterioseopic standard for milk, the writers admit the reasonableness of the figures adopted for certified milk in America. They point out, however, that such standards are not all-sufficient. Just as in the case of water, the kind of bacteria present and the whole past history of the milk must be reviewed before an absolute opinion could be given as to its suitability for food. Though this is perfectly true, it seems not untikely . . . that . bacterioscopic examination may prove as. useful for milk as similar examinations have proved for water, and that lust as an abnormal bacterial count in a well-water may put the medical officer on the q u i r i v e for surface contamination, so any great departure from the bacterioscopic standard for milk is a useful indicator of the milk having been improperly treated at some stage of its past history. Very interesting are the results given on p. 130 et sea]. of the writer's investigations of the bacterial content of milk, kept at various temperatures for varying periods. Though the results vary in each instance, there is at all temperatures a sudden rise in the number of bacteria, a sudden fall, a steady rise to a maximum, followed by a steady fall to ultimate sterility. The first rise is believed to be due to the development of various extraneous organisms, while the second tide is mainly due to the growth of lactic acid organisms. Many popular fallacies are exposed by the authors, notably the theory that the centrifugalization of milk will remove the bacteria. That this is a fallacy was sufficiently proved by the Bedford epidemic of 1902. In this case the milk was passed through a separator " to filter milk, removing tubercle and other disease germs." As a matter of fact, separated milk contains 25 per cent of the original organisms. The much-debated topic of bovine tuberculosis is naturally discussed at length. Pending the report of the present Royal Commission the writers have adopted the provisional attitude " t h a t tuberculosis in all animals is generically one and the same disease, but that it differs in various ways in different animals, and according to the strain and virulence of the infecting bacillus." They also hold that human and
February, 19041
Reviews
309
bovine tuberculosis a r e intercommunicable, but that " cross-infection is probably less common than is generally supposed." On the other hand, they distinctly point out that in their opinion tuberculous milk " i s being sold, not alone to the prejudice, but also to the risk, of the purchaser." It will be seen that this vexed question has been treated judicially, and indeed the whole chapter, which was written by Dr. Newman, merits careful study by those responsible for the control of milk and meat. In subsequent chapters milk-borne scarlatina, typhoid, and diphtheria are fully discussed, while a section on methods of enquiry into milk-borne disease is full of interest, though perhaps somewhat beyond the scope of the book. Lastly, Dr. Newman discusses the control of the milk supply by the State, by private enterprise, and by the trade, and ends with a summary of recommendations. These are in the main identical with those made by him to the Finsbury Council, and printed in the present issue o~ P u b l i c H e a l t h , * so need n o t be repeated here. Perhaps some regret will be felt that the authors have not seen their way to suggest new methods of controlling the milk trade. I t should, however, be remembered that short cuts are rarely practicable in Public Health work, and that true preventive work usually resolves itself into the old problems of removing filth and dispelling ignorance. In conclusion, we can only add that while this work is German in its thoroughness, it has one feature that is essentially British, namely, it does not emanate from a State department or richly endowed University, but from the private laboratory of one of the authors, who have by years of strenuous work rendered valuable service to the State and the Public Health Service. The book is superbly got up and illustrated with chromo lithographs, Woodburytype reproductions of photographs of cultures, and numerous blocks very beautifully executed and reproduced.
DIAGRAMS FOR THE USE OF CLASSES OF TECHNICAL INSTRUCTION FOR PLUMBERS. Price ls., 8~ in. by 5~ in., 26 pp. London: The Worshipful Company of Plumbers. The diagrams, about ~rth full size, are the first of a series intended to illustrate some of the more important scientific principles underlying the operations of the plumber ; types of apparatus ; the principles of their construction; and the workmanship employed in fitting them. The diagrams and accompanying descriptions comprise: Bends, corbel and washdown w.c.'s, hydrostatics, lead work, levers applied to ball valves, overflows and wastes, soil pipe joints, specific gravity, siphons, trap showing water seal, valve closet, ventilated sink waste and gutley. The diagrams are admirably executed, and will be of value not only to plumbers, but to those engaged in both the practice and study of sanitation. Fullsize diagrams (53 in. by 31 in.) are also obtainable for teaching purposes. Either set might be kept in the offices of local authorities for the benefit of builders, plumbers, and others. * See pages 254-290.