144 TEXT-BOOK OF BACTERIOLOGY. 



the return of the same species. This view was based chiefly on the 

 already-named circumstance that in the fermentation of lactic 

 acid, butyric acid, and urine, as also in the putrefying decomposi- 

 tion of the contents of the intestines, substances arise which at last 

 put a stop to the further development of the micro-organisms, the 

 originators of these processes, some of which even possess antisep- 

 tic properties and are hostile to bacterial life. A similar process 

 was supposed to take place in the body, the accumulated products 

 offering an enduring resistance to after-attacks from the same kind 

 of bacteria. 



The hypothesis of retention agrees with our views, in that it 

 regards the action of chemical substances as the chief factor. In 

 fact, Chauveau was led to the formulation of his theory by the 

 same considerations which we have been pursuing in our discus- 

 sions. He saw that the blood of animals suffering from anthrax 

 was able to grant immunity after having passed through a filter 

 impervious to bacteria. This filter was, indeed, no artificially-con- 

 structed instrument of plaster-of-Paris or porcelain, but a natural 

 one supplied by the body itself, the placenta. When he inoculated 

 ewes during the latter part of their pregnancy, first with attenu- 

 ated, then with full-strength anthrax bacilli, the lambs, when born, 

 were not susceptible to anthrax infection. 



From the formerly-made investigations of Brauell, and more 

 especially after those of Davaine, it had been considered as an as- 

 certained fact that the placenta formed an impenetrable partition, 

 a " barriere infranchissable," for micro-organisms of every kind. It 

 seemed, therefore, that the inoculative protection could only be 

 caused by soluble substances which passed from the maternal to 

 the foetal organism through the blood. 



But more recent experiments (I will only name those of Malvoz 

 and Jacquet) have shown that the placenta is by no means such 

 an impenetrable barrier for the progress of bacteria. The various 

 species of animals show differences in this respect, and the numerous 

 kinds of micro-organisms also. But it is beyond doubt that fre- 

 quently, especially when lacerations even the smallest take place 

 in the placenta, bacteria find their way into the circulation of the 

 embryo, and that this occurs frequently in cases of anthrax. For 

 this reason I purposely abstained from referring to this fact (im- 

 munity of lambs whose mothers had been inoculated during their 

 pregnancy) while endeavoring to prove the importance of the ex- 

 cretions in the question under discussion. We were able to cite so 

 many other convincing reasons in favor of our view that by this 

 alone the hypothesis of Chauveau is not disturbed. 



