2 6o HEREDITY AND DISEASE 



of function and environment, including, of course, food and drink. 

 Without there being any observable hereditary predisposition, 

 a man may acquire cirrhosis of the liver, neurasthenia, cardiac 

 hypertrophy, and so on through a long list. That a man may 

 be invaded by microbes without being in any way peculiarly 

 susceptible to them, or that he may be poisoned in a score 

 of ways without there being any constitutional weakness to 

 blame, seems certain. But are such acquired diseases in any 

 sense transmissible ? It seems to us that the answer should 

 be in the negative, but the general reasons for this answer 

 must be sought in the previous chapter — that dealing with the 

 transmissibility of acquired characters in general. 



No one can suppose that microbic diseases acquired by the 

 parent can be transmitted to the offspring, though there may 

 be ante-natal infection, and though the offspring may be pre- 

 judiced by the fact that the parents had the disease. If the 

 maternal constitution is seriously affected, it is probable enough 

 that the child may be born weakly, or imperfectly developed, 

 or even poisoned. In other words, the embryo is disadvan- 

 tageously modified by deficient or abnormal ante-natal nurture. 

 If the parental constitution is seriously affected it is possible 

 that the germ-cells may be likewise affected. This is most 

 (ikely in the case of the ova with their relatively larger cytoplasm 

 or formative cell-substance. In other words, there may be 

 a transmission of secondary effects of microbic disease. The 

 same will apply to any case where it can be definitely said that 

 the parental body is saturated with poisons or toxins. But to 

 admit this is very different from admitting that a specific modi- 

 fication of the parent's body can be transmitted to the offspring. 

 Yet some who should know better persist in calling this " a 

 distinction without a difference." 



Leprosy. — In a leprosy district the children of lepers may 

 exhibit the disease, but this may mean nothing more than that 

 they were exposed to the endemic conditions, whatever they may 



