326 SCIENCE PROGRESS. 



product, and the whole phenomenon ceases to be one of 

 heredity, for the hereditary transmission of micro-organisms 

 is simply a particular instance of bacterial infection. The 

 inheritance of actual specific disease must therefore always 

 be considered as a problem absolutely distinct from that 

 of heredity and incapable of explanation by any hypothesis 

 of heredity. 



Micro-organisms which reach an individual either by 

 inheritance or other modes of conveyance may undoubtedly 

 exhibit a period of latent life extending over many years ; 

 but when this condition is succeeded by an active life, to 

 establish the proof of an hereditary transmission is ex- 

 ceedingly difficult or even impossible (11). The early 

 researches into problems of this nature were necessarily 

 made with the help of statistical and clinical methods ; but 

 it is the application of experimental methods, which could 

 only be pursued with success as the study of bacteriology 

 developed, that has finally succeeded in removing the subject 

 of the hereditary transmission of specific diseases from the 

 hazy region of speculation. The attitude assumed by 

 Baumgarten and his followers on this question is well 

 known. In the case of tuberculosis it is maintained 

 that individuals are rarely infected with tubercle bacilli 

 after birth, but that the disease in the majority of cases is 

 due to a parasitic infection of the egg-cell or embryo. It 

 is even urged that the bacilli may remain latent in one 

 individual, and only enter upon a phase of activity in the 

 offspring, a view which, if correct, would accord with the 

 opinion of many clinical observers. While destroying the 

 opinion so commonly held that an "inherited tubercular 

 predisposition " exists, Baumgarten's theory of hereditary 

 parasitism makes a still greater demand on the imagina- 

 tion ; but that the views of this distinguished pathologist 

 have acted as a stimulus to renewed experimental work on 

 the transmission of micro-organisms is beyond doubt. 

 Recent papers by O. Lubarsch (2) of Rostock and J. 

 Csokor (3) of Vienna give an admirable exposition of the 

 present position of our knowledge on this subject of the 

 transference of bacteria from parent to offspring in man and 



