ESSAYS ON BACTERIOLOGY. 27 



of these bacteria. This by no means rules out the ex- 

 istence and importance of predisposing causes, but it 

 brings the chief and most direct factor into the fore- 

 ground, and limits the investigation to a narrower, 

 more definite and more pointed question. 



Do bacteria or their spores pass from parent to off- 

 spring with the beginning of or during intra-uterine 

 life? Does the fetus emerge from its mother's uterus 

 with the germs in its body? The light on this ques- 

 tion of heredity has heretofore come chiefly from a 

 clinical rather than a pathological source. An im- 

 mense mass of clinical facts has been gathered, but 

 has not sufficed to settle the whole matter. Notably 

 is this tmcertainty true of tuberculosis, that disease in 

 ■connection with which the study of heredity is of such 

 importance. Many cases have been recorded which 

 seem to prove that certain infectious diseases may be 

 transmitted to the fetus, as smallpox and measles. 

 Further, it seems to have been shown that the bacilli 

 of anthrax may pass from the mother to the young in 

 Titero. "We have, then, apparent proof of hereditary 

 transmission of an infectious disease whose bacteria, if 

 such exist, are not known, and of one with whose bac- 

 teria we are thoroughly acquainted. It seems, there- 

 fore, not unreasonable to suppose, the supposition be- 

 ing strengthened by the well-known clinical facts, 

 that such a disease as tuberculosis may be acquired 

 before birth. Parties are divided on this question, 

 some holding the opinion expressed by Whittaker, 



