HEREDITY AND DISEASE 1 O.J 



more accurately. The entrance of bacilli from the 

 body of the mother into the body of an unborn 

 child is not to be distinguished from the point of 

 view of the student of heredity, from the infection 

 of the child, after birth, by bacilli derived from the 

 mother; nor is this to be distinguished from the 

 spread of infection from the mother to any other 

 child or adult. It is, doubtless, of great pathological 

 and practical interest and importance to discuss 

 the possibilities of the infection of the embryo, or 

 foetus, by the mother, but the presence of tubercle 

 bacilli in the child at birth, as a result of such in- 

 fection, should properly be called conigp/nital not 

 hereditary tuberculosis. One organism living within 

 another which is the host of a parasite, such as the 

 tubercle bacillus, may well be specially liable to infec- 

 tion ; but that fact is of little interest to the student of 

 heredity, which is the tendency of like to beget like. 



The point must be insisted ujxai, for current 

 medical and popular nomenclature takes no cog- 

 nisance of what is really a cardinal distinction. The 

 ante-natal infection of an embryo, or foetus, is a 

 special problem in the general subject of infection. 

 Strictly speaking, it has nothing whatever to do with 

 the subject of heredity. Another instance, by no 

 means uncommon, is worthy of citation. Tin- 

 disease known as acute rheumatism, or rheumatic 

 fever, is due to a particidar microbe called the 

 diplococcus rheumaticvs. This microbe not infre- 

 quently attacks a pregnant woman. During the 

 course of her attack of rheumatic fever, the poisons 

 produced by the diplococcus circulate through her 

 blood, and only too often attack the valves of her 



