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Heredity and tuberculosis
REVIEWS
AND NOTICES
OF BOOKS
261
REVIEWS AND NOTICES OF BOOKS. HEREDITY
AND
TUBERCULOSIS.
I
I~ an extremely interesting memoir Professor Karl Pearson dwells on the difficulty and labour of gathering together family histories Sufficiently numerous, accurate, and complete to serve as adequate bases for statistical investigation. Those of us who have attempted, and abandoned in despair, the task in relation to insanity are likely to sympathize with him. Liars and experts are thought to represent progressive orders of demerit. ]But probably patients who answer unwelcome questions descend in many cases to depths unplumbed even by the traditional expert. Thus Professor Pearson's data indicate at first sight that phthisis is more common in the families of women than of men, which, of course, is nonsense. The families are identical, the truth, as surmised by him, being that women are more interested in, know more about, and are more ready to impart information, correct or incorrect, concerning their family histories than men. H e reaches three main conclusions: (I) " The allimportant genetic fact that the diathesis of pulmonary tuberculosis is undoubtedly inherited, and that the intensity of this inheritance is comparable with that found for normal physical characters in man." (2) " T h a t the risks run, especially under urban conditions, are for tuberculosis, as for a number of other diseases, so great that the constitution or diathesis means almost everything for the individual whose life cannot be spent in self-protection." (3) T h e inheritance of the diathesis is not Mendelian--that is, offspring and descendants do not reproduce the character of one parent to the complete exclusion of the character of the other. The first and third conclusions are quite certainly correct. T h e y m a y be confirmed by incontrovertible independent evidence. Certain races of m e n - - f o r example, American I n d i a n s - - a r e so highly susceptible to tuberculosis that since the introduction of the disease from Europe they are unable to persist in settled communities, especially under urban conditions, and more especially in such dark and ill-ventilated houses as Europeans construct in cold and temperate climates. Other r a c e s - - f o r example, American negroes - - a r e able to persist in Northern cities, but their death-rate is then very high. " E v e r y other adult negro succumbs to it." Yet other races--for instance, the B r i t i s h - - a r e still more resistant. Races are merely aggregates of related individuals. Obviously, therefore, the indi~eiduals of each race must tend to transmit their degrees of susceptibility to offspring and descendants. Again, Europeans have interbred with the aborigines in N o r t h and South America. In the latter a mixed' race has resulted, which, presumably, blends the diatheses of both races. In the former, where the conditions are more onerous, the half-breeds and their descendants are few, and are restricted mainly 1 "A First Study of the Statistics of Pulmonary Tuberculosis." ('Draper Company's Research Memoirs.) By Karl Pearson, M.A., LL.B., F.R.S., Professor of Applied Mathematics and Mechanics, University College, London. London: x9o7.
262
THE
BRITISH
JOURNAL
OF TUBERCULOSIS
to the back settlements. T h e y perish under the conditions found in Northern cities. H a d the inheritance been Mendelian, a proportion of them would have inherited the high resisting power of the whites, and a mixed race would have been founded, as in Central and South America. The evidence for the second conclusion is less convincing. At any rate, I think the case is stated too strongly. Doubtless urban dwellers almost daily or hourly inhale or ingest some tubercle bacilli. But dosage plays an important part in infection. In some homes and occupations the liability to receive a dose of bacilli large enough to cause disease is far greater than under other conditions. Moreover, it is in just such homes and occupations that the resisting power of the individual is most lowered--that the innate diathesis is most altered by subsequent acquirement. Environment, therefore, is a considerable factor--obviously so, since an environment in which the average ]Briton can dwell in safety is dangerous to the American negro and deadly to the Red Indian. In the slums of our cities the conditions are dangerous even for the average Briton and deadly for the weaker members of his race. The recent fall in the mortality from phthisis has been so rapid that it cannot be attributed to an improvement in the race, but only to an improvement in the environment. T h e fact that m a n y people who succumb to phthisis when they are approaching middle age escape meningeal and abdominal tuberculosis during infancy and puhnonary tuberculosis during youth is evidence that a fatal dose of bacilli is not, under ordinary circumstances, to be acquired every day by the average individual who is in normal health. Nevertheless, Professor Pearson is well within the mark when he declares that " there is an antisocial disregard for national eugenics in the conduct of medical men who can write to the public press that marriage or even intermarriage of members of tuberculous stocks is of no social detriment, provided they live with a good supply of fresh air." Under such conditions as prevail in England, no amount of air can secure immunity to the members of a susceptible stock. Often, however, it secures life sufficiently prolonged to increase the n u m b e r of sufferers in the next generation. G . ARCHDALL REID, M . B .
THE BLOOD IN PULMONARY TUBERCULOSIS. 1 Dr. R. Kjer-Petersen, in his work on the numerical relations of the leucocytes in pulmonary tuberculosis, has had to meet the difficulty that the ordinary methods of counting the white corpuscles in the blood are very defective, and the normal figures for healthy men and women have not been quite accurately ascertained. According to the author, the number of leucocytes in blood taken on awaking in the morning is fairly constant for healthy men--generally between 4,ooo and 5,ooo in the cubic millimetre--whereas for healthy women it m a y vary between 3,000 and 24,000. T h e counts made during menstrual periods give relatively low i~g.ures; at all events, the highest figures are never found at these tlmes~ T h e author thinks that the daily leucocyte increase is n o t dependent on digestion. F o r ordinary clinical purposes, he recommends that leucocyte-counts 1 ,,Ueber die numerischen Verh~ltnisse der Leukocyten bei der Lungentuberkulose." Von Dr. Med. R. Kjer-Petersen. Pp. 2I 7. Nineteen plates. "vVfirzburg : A. Stuber. I9o6.
AND NOTICES
OF BOOKS
261
REVIEWS AND NOTICES OF BOOKS. HEREDITY
AND
TUBERCULOSIS.
I
I~ an extremely interesting memoir Professor Karl Pearson dwells on the difficulty and labour of gathering together family histories Sufficiently numerous, accurate, and complete to serve as adequate bases for statistical investigation. Those of us who have attempted, and abandoned in despair, the task in relation to insanity are likely to sympathize with him. Liars and experts are thought to represent progressive orders of demerit. ]But probably patients who answer unwelcome questions descend in many cases to depths unplumbed even by the traditional expert. Thus Professor Pearson's data indicate at first sight that phthisis is more common in the families of women than of men, which, of course, is nonsense. The families are identical, the truth, as surmised by him, being that women are more interested in, know more about, and are more ready to impart information, correct or incorrect, concerning their family histories than men. H e reaches three main conclusions: (I) " The allimportant genetic fact that the diathesis of pulmonary tuberculosis is undoubtedly inherited, and that the intensity of this inheritance is comparable with that found for normal physical characters in man." (2) " T h a t the risks run, especially under urban conditions, are for tuberculosis, as for a number of other diseases, so great that the constitution or diathesis means almost everything for the individual whose life cannot be spent in self-protection." (3) T h e inheritance of the diathesis is not Mendelian--that is, offspring and descendants do not reproduce the character of one parent to the complete exclusion of the character of the other. The first and third conclusions are quite certainly correct. T h e y m a y be confirmed by incontrovertible independent evidence. Certain races of m e n - - f o r example, American I n d i a n s - - a r e so highly susceptible to tuberculosis that since the introduction of the disease from Europe they are unable to persist in settled communities, especially under urban conditions, and more especially in such dark and ill-ventilated houses as Europeans construct in cold and temperate climates. Other r a c e s - - f o r example, American negroes - - a r e able to persist in Northern cities, but their death-rate is then very high. " E v e r y other adult negro succumbs to it." Yet other races--for instance, the B r i t i s h - - a r e still more resistant. Races are merely aggregates of related individuals. Obviously, therefore, the indi~eiduals of each race must tend to transmit their degrees of susceptibility to offspring and descendants. Again, Europeans have interbred with the aborigines in N o r t h and South America. In the latter a mixed' race has resulted, which, presumably, blends the diatheses of both races. In the former, where the conditions are more onerous, the half-breeds and their descendants are few, and are restricted mainly 1 "A First Study of the Statistics of Pulmonary Tuberculosis." ('Draper Company's Research Memoirs.) By Karl Pearson, M.A., LL.B., F.R.S., Professor of Applied Mathematics and Mechanics, University College, London. London: x9o7.
262
THE
BRITISH
JOURNAL
OF TUBERCULOSIS
to the back settlements. T h e y perish under the conditions found in Northern cities. H a d the inheritance been Mendelian, a proportion of them would have inherited the high resisting power of the whites, and a mixed race would have been founded, as in Central and South America. The evidence for the second conclusion is less convincing. At any rate, I think the case is stated too strongly. Doubtless urban dwellers almost daily or hourly inhale or ingest some tubercle bacilli. But dosage plays an important part in infection. In some homes and occupations the liability to receive a dose of bacilli large enough to cause disease is far greater than under other conditions. Moreover, it is in just such homes and occupations that the resisting power of the individual is most lowered--that the innate diathesis is most altered by subsequent acquirement. Environment, therefore, is a considerable factor--obviously so, since an environment in which the average ]Briton can dwell in safety is dangerous to the American negro and deadly to the Red Indian. In the slums of our cities the conditions are dangerous even for the average Briton and deadly for the weaker members of his race. The recent fall in the mortality from phthisis has been so rapid that it cannot be attributed to an improvement in the race, but only to an improvement in the environment. T h e fact that m a n y people who succumb to phthisis when they are approaching middle age escape meningeal and abdominal tuberculosis during infancy and puhnonary tuberculosis during youth is evidence that a fatal dose of bacilli is not, under ordinary circumstances, to be acquired every day by the average individual who is in normal health. Nevertheless, Professor Pearson is well within the mark when he declares that " there is an antisocial disregard for national eugenics in the conduct of medical men who can write to the public press that marriage or even intermarriage of members of tuberculous stocks is of no social detriment, provided they live with a good supply of fresh air." Under such conditions as prevail in England, no amount of air can secure immunity to the members of a susceptible stock. Often, however, it secures life sufficiently prolonged to increase the n u m b e r of sufferers in the next generation. G . ARCHDALL REID, M . B .
THE BLOOD IN PULMONARY TUBERCULOSIS. 1 Dr. R. Kjer-Petersen, in his work on the numerical relations of the leucocytes in pulmonary tuberculosis, has had to meet the difficulty that the ordinary methods of counting the white corpuscles in the blood are very defective, and the normal figures for healthy men and women have not been quite accurately ascertained. According to the author, the number of leucocytes in blood taken on awaking in the morning is fairly constant for healthy men--generally between 4,ooo and 5,ooo in the cubic millimetre--whereas for healthy women it m a y vary between 3,000 and 24,000. T h e counts made during menstrual periods give relatively low i~g.ures; at all events, the highest figures are never found at these tlmes~ T h e author thinks that the daily leucocyte increase is n o t dependent on digestion. F o r ordinary clinical purposes, he recommends that leucocyte-counts 1 ,,Ueber die numerischen Verh~ltnisse der Leukocyten bei der Lungentuberkulose." Von Dr. Med. R. Kjer-Petersen. Pp. 2I 7. Nineteen plates. "vVfirzburg : A. Stuber. I9o6.