132 THE PRINCIPLES OF HEREDITY 



209. On the other hand, if a healthy mother bear diseased 

 children to an infected father we should, if our theory be 

 correct, expect to find (and actually we do find) that each 

 succeeding infant exhibits less and less signs of the disease ; 

 and this notwithstanding the fact, other things being equal, 

 that the last child infected by a diseased father, tends, when 

 born to a different woman who has not previously suffered 

 from the disease or borne infected children, to have the 

 complaint as deeply as the first ; in other words, a woman, 

 who has once borne an infected child, tends to endow suc- 

 ceeding infected children with greater and greater powers of 

 resistance; the increased powers of resistance being clearly 

 derived from her and not from the father, since the women, 

 who have not been themselves infected nor borne infected 

 children, may bear deeply diseased children to the same 

 father. Here, in the case of the former woman, toxins from 

 each infected child pass into the circulation of the non- 

 infected mother, inducing a more and more perfect reaction 

 in each succeeding pregnancy; and, therefore, in each suc- 

 ceeding pregnancy there are elaborated by her more and more 

 digestive bodies, which at length attenuate the toxins so 

 thoroughly that the cells of the child are able to react and 

 the child survives, instead of perishing like its predecessors. 

 In this case toxins pass from the child to the mother, while 

 from the mother to the child pass attenuated toxins and 

 digestive substances. 



210. It follows as a corollary, if a mother, who has acquired 

 immunity either by personal disease or by bearing infected 

 children, become pregnant of an infected embryo, she will 

 tend to confer immunity on it, since the elaboration of toxins 

 in the latter will tend to call forth the elaboration of digestive 

 bodies in her; but, if the embryo be not infected, then 

 immunity will not be conferred ; for in such a case no toxins 

 from the child will call forth the digestive bodies from the 

 mother; and these, as we have seen, do not persist in the 

 body in the absence of appropriate stimulation i. e. in the 



immune, for no observations bearing on the subject appear to have been 

 published. Nevertheless, reasoning from the analogy of other diseases 

 we may be sure they are not. It is a matter of common knowledge that 

 the children of mothers recovered from and immune to whooping-cough, 

 measles, scarlatina, small-pox, and other diseases, are not immune. On 

 the other hand, the children of mothers who, during pregnancy, have 

 suffered from small-pox have been found immune ; and Chauveau claims 

 to have proved that the offspring of sheep suffering from anthrax, have, 

 under similar circumstances, exhibited immunity against that disease. 



