4. It is probable, but less so,50 that, the mother being healthy and the father syphilitic, the child will be infected.
50 This refers simply to the comparative probability of infection, and does not conflict with the statistical fact expressed by Hutchinson (Reynolds's System of Medicine, vol. i. p. 431) in his words: "In the large proportion of cases met with in practice the taint is derived from the father only." This numerical predominance of paternal influence is very readily explained. There are many more syphilitic men than syphilitic women, and especially among the couples who contract fertile marriages the number of women who are infected before becoming mothers is inconsiderable. On the other hand, it frequently happens that men who have had syphilis, but have been without symptoms for a longer or shorter interval, marry and transmit to a series of children a disease which has ceased to be directly contagious to their wives, the transmissive power continuing after the possibility of ordinary contagion has disappeared. As in the majority of such women the disease is latent, and may be only displayed in their immunity from infection, it becomes evident that, history and symptoms both being wanting on their part, the conditions justify the assertion of Mr. Hutchinson. (See Nouveau Dict. de Médecine et Chirurgie, p. 684.)
That assertion (quoted above) has, however, been thought by several writers to indicate his belief in the escape of the mother. That I have not misinterpreted him is evident from the following extract from an article on "The Transmission of Syphilis," written by him (Brit. and For. Med.-Chir. Rev., Oct., 1877): "I take it for granted (although I know that there are still some who doubt) that it is possible for a father to transmit the taint, the mother being at the time of conception wholly free. I believe, indeed, that in practice this is by far the most common way in which syphilis is transmitted. Whether in these cases it is correct to speak of the inheritance being paternal only is, as we have just seen, another matter, since it is possible that in every instance the mother derives an infection from the father, and may thus in turn influence it."
5. It is highly probable, though it can hardly be considered as proven, that in all cases where a child becomes syphilitic through paternal influence the mother is also the subject of syphilis, which may, however, assume a latent form, the only evidence of its presence in a few cases being the protection which it affords against contagion through the medium of the child.
6. Syphilis may be transmitted from mother to child even when it is acquired by the former as late as the seventh month of utero-gestation.
Since writing the above the thirty-fourth volume of the Nouveau Dictionnaire de Médecine et de Chirurgie has been published. In the article on syphilis seventeen pages are devoted to the question of heredity, which is reviewed in a most thorough manner and finally summed up as follows (p. 698):
"The most definite views which we possess on the subject of the hereditary transmission of syphilis may be thus expressed:
"Children may be infected by heredity, not only when the two parents are syphilitic, but also when only one, either the father or mother, is diseased at the time of conception.
"When both parents are diseased at that time there is more certainty that the child will be infected, and infected gravely, than if only one of them has the pox.
"The hereditary disease is not always fatal, even when both progenitors have actual specific symptoms. The more recent the disease of the parents the greater the chances of their transmitting the disease and of its assuming a serious form. There is no proof that inherited syphilis is more grave when derived from the father than when coming from the mother.