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THE SIZE OF INFLUENZA A VIRUS
588 mouths by a team of dental surgeons, biochemists, dietitians and social workers might produce far-reaching results and do more to offset the shortage of dentists than schemes for increasing the supply. It would, I feel sure, prove the soundness of Professor Ryle’s constant appeal that the study of the healthy should keep pace with the study of the unfit. GUY NEELY. Blackheath. --
LEUCOCYTE
COUNTS IN RADIUM WORKERS SIR,—In your issue of Sept. 4 (p. 289) ur. U. j.u. Britton drew attention to a low level of leucocyte counts occurring among healthy nurses of the Middlesex Hospital, not exposed to radium. I have also noticedthis among nurses at Mount Vernon, and among normal young males beginning_ radium work and not connected with any hospital. It seems likely that this is a war-time effect, worth the while of some public body like the Ministry of Health to investigate, to see how far it egterids in the population, and -to seek its cause. It is to be noted in Britton’s counts that whereas 20’1% were below the level of 3000 polymorphs per c.mm., only 8-1% were below the level of 1500 lymphocytes. Thus the lymphocytes are much less effected. So by discarding the polymorph count and relying on the lymphocyte, it remains possible to rely upon blood-counts to determine whether workers should or should not continue handling X rays and radium. Several radium workers under my care have recently shown progressive falls in polymorph counts not accompanied by lymphocyte falls, and have been permitted to continue with their work. I do not agree with Britton that weekly counts would solve the difficulty. Among radium workers the fall in leucocytes -is to be detected not in weeks but in months .or years, and could not thus be distinguished from the war-time effect to which he draws attention. J. C. MOTTRAM. Mount Vernon Hospital, Northwood. THE
SIZE
HIPPURIC-ACID EXCRETION AND URINE VOLUME SIR,—In your issue of Oct. 16 Major Allan Palmer, confirming the findings of Machella et al., reports a positive correlation between the amount of hippuric acid (HA) excretion and urine volume, using Quick’s intraThis was evident venous modification of the test. particularly in tests where the urine volume was below 150 c.cm. and he concludes that abnormally low HA values obtained in a urine volume below 150 c.cm. may be inaccurate. This conclusion, on the evidence presented, is open- to criticism. It is a well-established fact/ not mentioned by either investigator, that patients with hepatic disturbances have a tendency to delayed excretion of water and oliguria. One would expect, therefore, to find a tendency to low urine volumes in association with low excretion of HA, both presumably being related to the same underlying disorder. In my experience with the intravenous modification of the test, using Weichselbaum and Probstein’s (1939) analytical technique, and giving 200,c.cm. of water at the time of the injection (as is recommended by Dr. Palmer), many patients and normals show " normal " and even " optimal " excretion of HA in the first hour despite urine volumes below 150 c.cm. and even below 100 c.cm. To consider a subnormal output of HA in a " low " urine volume as " inaccurate " seems to me objectionable, since the frequent association of low urine volumes with low HA output does not necessarily imply that the one directly causes the other. In fact, while I find, on plotting excretion of HA against volume in some 180 tests, a certain tendency for the low HA values to be associated with low urine volumes, the correlation is not strict. In follow-up studies with serial tests in individual patients the lack of correlation is striking, and it becomes clear that a large urine volume need not cause an increase in the output of HA or vice versa. To illustrate this may I quote the following data from five patients with gastric ulcer :
OF INFLUENZA A VIRUS
SIR,—Dr. Kenneth Smith’s letter in your issue of Oct. 23 prompts me to mention briefly some experiments conducted, in collaboration with the late Miss Dora Lush, soon after American workers first intimated that they regarded the true size of influenza virus to be about 15 mµ. This figure was the outcome of studies with the virus propagated in 10-day-old hens’ eggs, whereas earlier work with the virus obtained from the lungs of flu-infected mice had indicated a particle size 80-100 mµ. We accordingly analysed allantoic and amniotic fluids from eggs infected with influenza A virus, employing the methods of ultrafiltration and centrifugation. During the limited attention we could devote to the problem at that time, no evidence was found for the existence of the extremely small phase of the virus. Likewise, virus that had been precipitated with salmine and re-dispersed .
showed the same order of size as virus before such treatment. It should also be mentioned that Friedewald and Pickles (Proc. Soc. exp. Biol. Med. 1943, 52, 261) have recently reported having submitted influenza-infected allantoic fluid to centrifugation analysis, and, following a different technique from our own, find the size of the virus to be at least 60 my. Our values by two alternative centrifugation methods ranged from 60 to 90 m,u. In my opinion, you were wholly justified in your criticism of the hasty acceptance of the small figure for the size of influenza virus by Dr. Smith in his generally admirable booklet Beyond the Microscope. National Institute for Medical Research, N.W.3.
W. J. ELFORD.
* * Current opinion as to the size of viruses is based upon the results of differential filtration through graded collodion membranes, centrifugation and at times optical methods ; data so obtained by these three methods have on the whole yielded concordant results. Chambers and Henle have recently thrown doubt on the conclusions thus reached as to the size of influenza virus. The exact size of this virus is in itself relatively unimportant, but their claims, if correct, throw doubt on most of what is now accepted as to the sizes of viruses in general. The claims have, however, not yet carried general conviction, especially in this country.-ED. L.
*
Post-oP.
The observation of Machella et al. that induction of diuresis by say 1000 c.cm. of water before the test may increase the output of HA, requires closer study since no account was taken of possible spontaneous day-to-day variations in an upward direction. H. POLLAK. NOT SO DREARY
pitals controlled by the Middlesex County Council are admittedly excellent, but by no stretch of imagination can they be considered representative of the conditions prevailing in municipal hospitals throughout the country. The rateable value of the county of Middlesex, is the highest in the world ; therefore considerably more money is available for hospital development. In the majority of municipal hospitals the position of the senior members of the staff has deteriorated steadily since the outbreak of
war
and
favourably with the position practitioners.
now
of the
compares very
un-
majority of general
I do not propose to waste space by going through the list of amenities mentioned in the letter of Dr. Avery Jones in your issue of Oct. 23, but I can safely say that in the average municipal hospital not one of them would be found to exist. ASSISTANT MEDICAL OFFICER. 1. Adler, A. Klin. Wschr. 1923, 2, Arch. inn. Med. 1934, 25, 269.
1980 ; Adlersberg, D. Wien.
LEUCOCYTE
COUNTS IN RADIUM WORKERS SIR,—In your issue of Sept. 4 (p. 289) ur. U. j.u. Britton drew attention to a low level of leucocyte counts occurring among healthy nurses of the Middlesex Hospital, not exposed to radium. I have also noticedthis among nurses at Mount Vernon, and among normal young males beginning_ radium work and not connected with any hospital. It seems likely that this is a war-time effect, worth the while of some public body like the Ministry of Health to investigate, to see how far it egterids in the population, and -to seek its cause. It is to be noted in Britton’s counts that whereas 20’1% were below the level of 3000 polymorphs per c.mm., only 8-1% were below the level of 1500 lymphocytes. Thus the lymphocytes are much less effected. So by discarding the polymorph count and relying on the lymphocyte, it remains possible to rely upon blood-counts to determine whether workers should or should not continue handling X rays and radium. Several radium workers under my care have recently shown progressive falls in polymorph counts not accompanied by lymphocyte falls, and have been permitted to continue with their work. I do not agree with Britton that weekly counts would solve the difficulty. Among radium workers the fall in leucocytes -is to be detected not in weeks but in months .or years, and could not thus be distinguished from the war-time effect to which he draws attention. J. C. MOTTRAM. Mount Vernon Hospital, Northwood. THE
SIZE
HIPPURIC-ACID EXCRETION AND URINE VOLUME SIR,—In your issue of Oct. 16 Major Allan Palmer, confirming the findings of Machella et al., reports a positive correlation between the amount of hippuric acid (HA) excretion and urine volume, using Quick’s intraThis was evident venous modification of the test. particularly in tests where the urine volume was below 150 c.cm. and he concludes that abnormally low HA values obtained in a urine volume below 150 c.cm. may be inaccurate. This conclusion, on the evidence presented, is open- to criticism. It is a well-established fact/ not mentioned by either investigator, that patients with hepatic disturbances have a tendency to delayed excretion of water and oliguria. One would expect, therefore, to find a tendency to low urine volumes in association with low excretion of HA, both presumably being related to the same underlying disorder. In my experience with the intravenous modification of the test, using Weichselbaum and Probstein’s (1939) analytical technique, and giving 200,c.cm. of water at the time of the injection (as is recommended by Dr. Palmer), many patients and normals show " normal " and even " optimal " excretion of HA in the first hour despite urine volumes below 150 c.cm. and even below 100 c.cm. To consider a subnormal output of HA in a " low " urine volume as " inaccurate " seems to me objectionable, since the frequent association of low urine volumes with low HA output does not necessarily imply that the one directly causes the other. In fact, while I find, on plotting excretion of HA against volume in some 180 tests, a certain tendency for the low HA values to be associated with low urine volumes, the correlation is not strict. In follow-up studies with serial tests in individual patients the lack of correlation is striking, and it becomes clear that a large urine volume need not cause an increase in the output of HA or vice versa. To illustrate this may I quote the following data from five patients with gastric ulcer :
OF INFLUENZA A VIRUS
SIR,—Dr. Kenneth Smith’s letter in your issue of Oct. 23 prompts me to mention briefly some experiments conducted, in collaboration with the late Miss Dora Lush, soon after American workers first intimated that they regarded the true size of influenza virus to be about 15 mµ. This figure was the outcome of studies with the virus propagated in 10-day-old hens’ eggs, whereas earlier work with the virus obtained from the lungs of flu-infected mice had indicated a particle size 80-100 mµ. We accordingly analysed allantoic and amniotic fluids from eggs infected with influenza A virus, employing the methods of ultrafiltration and centrifugation. During the limited attention we could devote to the problem at that time, no evidence was found for the existence of the extremely small phase of the virus. Likewise, virus that had been precipitated with salmine and re-dispersed .
showed the same order of size as virus before such treatment. It should also be mentioned that Friedewald and Pickles (Proc. Soc. exp. Biol. Med. 1943, 52, 261) have recently reported having submitted influenza-infected allantoic fluid to centrifugation analysis, and, following a different technique from our own, find the size of the virus to be at least 60 my. Our values by two alternative centrifugation methods ranged from 60 to 90 m,u. In my opinion, you were wholly justified in your criticism of the hasty acceptance of the small figure for the size of influenza virus by Dr. Smith in his generally admirable booklet Beyond the Microscope. National Institute for Medical Research, N.W.3.
W. J. ELFORD.
* * Current opinion as to the size of viruses is based upon the results of differential filtration through graded collodion membranes, centrifugation and at times optical methods ; data so obtained by these three methods have on the whole yielded concordant results. Chambers and Henle have recently thrown doubt on the conclusions thus reached as to the size of influenza virus. The exact size of this virus is in itself relatively unimportant, but their claims, if correct, throw doubt on most of what is now accepted as to the sizes of viruses in general. The claims have, however, not yet carried general conviction, especially in this country.-ED. L.
*
Post-oP.
The observation of Machella et al. that induction of diuresis by say 1000 c.cm. of water before the test may increase the output of HA, requires closer study since no account was taken of possible spontaneous day-to-day variations in an upward direction. H. POLLAK. NOT SO DREARY
pitals controlled by the Middlesex County Council are admittedly excellent, but by no stretch of imagination can they be considered representative of the conditions prevailing in municipal hospitals throughout the country. The rateable value of the county of Middlesex, is the highest in the world ; therefore considerably more money is available for hospital development. In the majority of municipal hospitals the position of the senior members of the staff has deteriorated steadily since the outbreak of
war
and
favourably with the position practitioners.
now
of the
compares very
un-
majority of general
I do not propose to waste space by going through the list of amenities mentioned in the letter of Dr. Avery Jones in your issue of Oct. 23, but I can safely say that in the average municipal hospital not one of them would be found to exist. ASSISTANT MEDICAL OFFICER. 1. Adler, A. Klin. Wschr. 1923, 2, Arch. inn. Med. 1934, 25, 269.
1980 ; Adlersberg, D. Wien.