THE CAUSATION OF DISEASE J I 



by the two sexes than when the acquired structural change is 

 strictly local. In such a disease as chronic gout, one would 

 therefore expect the female progeny to be more or less affected, 

 because, although two of the above conditions are fulfilled — 

 namely, (i) the operation of the specific E upon one sex for 

 many generations, (2) its operation during the sexual period of 

 life — nevertheless the third condition is absent — to wit, strict 

 localization of the acquired structural change ; for in chronic 

 gout, although the primarily erring tissue may be strictly local, 

 the tissues are more or less universally depraved. But if we 

 suppose a gout-producing E to affect a limited set of tissues in 

 the male throughout countless generations without causing any 

 general depravity of health — which, however, is impossible — 

 we might predict, with a fair measure of certainty, that the 

 affection would appear chiefly, if not solely, in the males — the 

 female line escaping. In a similar way the antlers of the stag 

 have been acquired ; but it is worthy of note that rudimentary 

 antlers also appear in the female, showing that the hereditary 

 transmission is not entirely confined to the one sexual line. 



Wherefore the doctrine of sexual heredity may be thus 

 enunciated : the more exclusively a specific E acts upon one sex, 

 the greater the number of generations acted upon, and the more 

 limited the affected tissue, the more apt is the resulting variation 

 to pick out that one sex in the offspring. Moreover, a character 

 is more apt to be transmitted along one sex when it is acquired 

 during the period of sexual activity, and it is probably more apt 

 to attach itself to the male than to the female sex. Nevertheless, 

 in all cases there is a tendency for the opposite sex to be affected. 



From the above observations on sexual heredity, it is mani- 

 fest that sex influences structure. It may thus be a predis- 

 posing cause of disease. Sex may further predispose to disease 

 in so far as it determines occupation, and therefore the ex- 

 ternal-body-E, mental and physical. 



The influence of sex in determining the heredity of par- 

 ticular diseases is a subject still requiring careful investigation. 

 Patient and laborious statistical work is needed to clear up 

 many points on which we are still ignorant. Meanwhile, how- 

 ever, much error may be averted by keeping this principle of 

 sexual heredity clearly before us. Ignorance of it is continually 

 leading to wrong conclusions. 



