2a TUBERCULOSIS, HEREDITY 



of infection under urban conditions, but in the great 

 bulk of cases a predisposition, a phthisical diathesis 

 must exist, to render the risk a really great one.' 



Notwithstanding that distinct statement of my posi- 

 tion, a leading medical member of the Sociological 

 Society believes it possible to confute the observed facts 

 with regard to phthisis recorded in this Laboratory by 

 the asseveration that biometricians measure everything 

 but life and that the Director of the Biometric Laboratory 

 has no knowledge of the tubercle bacillus! Other 

 medical critics — possibly of more weight in the profes- 

 sion — seem equally at sea when they have to deal with the 

 interpretation of the most elementary problem in statistics. 

 Dr. Leslie Mackenzie seeks refuge in the suggestions ^ 

 that the paternal germ-cell may carry the tubercle 

 bacillus to the offspring and that such early infected 

 cases may remain latent for twenty or thirty years 

 after. * I do not fabricate hypotheses,' wrote Newton, 

 and the business of the trained man of science is not 

 to suggest what may or may not be, but to accumulate 

 facts and find out what actually is. The tubercle 

 bacillus is not invisible ; let the man of science turn to 

 his microscope, and not scatter hypotheses broadcast in 

 popular journals, where they pass for proven facts. 



Still another eminent medical man in high official 

 position asserted that I went beyond my data in stating 

 that ' few individuals who lead a moderately active life 

 can escape an almost daily risk of infection under urban 

 conditions '. Here we come to the very kernel of the 

 matter : — if the tubercle bacillus be ubiquitous, the differ- 

 ence between man and man cannot be a question of 



1 Sociological Review, vol. iii, p. 308. If the suggestion were demonstrated, 

 the remedy would lie in the celibacy of the tuberculous, not in the separation 

 of parent and offspring after birth, i. e. it would be eugenic. 



