SECONDARY EFFECTS OF DISEASE 271 



offspring, though it is theoretically different, may result if the 

 toxins in the maternal body affect not the ova, but the developing 

 embryo. They may saturate through the placenta and disturb 

 the normal course of development. This would be an ante-natal 

 modification, and we should not expect its consequences to 

 extend beyond the immediate offspring, unless the same detri- 

 mental conditions persisted in subsequent generations. 



Illustrations. " Assume that the last egg of a fowl dying from 

 tuberculosis is fertile. Weismann would admit every one would 

 that the chick is likely not to be full-grown and robust. It will 

 fail of ' nutrition,' of a full capacity for regeneration, and of normal 

 resistiveness to environment (terms which require fuller considera- 

 tion). It would appear, then, that this chick has an idiopathic [say, 

 innate] susceptibility to all and sundry, or at least to several, 

 diseases. It is mere slackness to call that heredity in disease. 

 It is equally apt to be variation ; the chick turning out to be epileptic, 

 or deformed, or liable to cholera. That is all that Weismann con- 

 tends for. The disease has not bred itself" (Dr. George Wilson, 

 Scot. Med. Surg. Journ. vi. 1900, p. 321). 



Martius puts this problem. Two brothers have the same medium 

 predisposition to tuberculosis ; both take measles. During con- 

 valescence one (A) becomes definitely tuberculous as the result 

 of exposure; the other (B) has his predisposition increased but 

 resists tubercle-infection. Both marry normal wives and have 

 children. Now, will the children of A have a worse inheritance 

 than the children of B ? There seems no reason to answer in the 

 affirmative, unless it can be shown that the toxins, etc., engendered 

 by the progress of the disease so saturate through the whole system 

 that the germ-cells also are specifically affected and thus have 

 their predisposition exaggerated. This seems very improbable. 

 But it is possible that when a disease goes far the germ-cells may 

 be in a general way prejudicially affected. And if they are rendered 

 in a general way less vigorous, there is some likelihood that the 

 disorganisation of the germinal machinery may go further. 



It is interesting to inquire whether, in cured cases of phthisis 

 and the like, the protective substances naturally produced, e.g. 

 the ' tulase ' of Behring, might not even lessen the heritable 

 predisposition of the ovum towards the disease in question. 



