SEVENTH LECTURE. 



POISONS. 



In this lecture I propose to examine more particularly the 

 evidence given by experimenters of the finding of the poison- 

 ous products of micro-organisms. 



Koch, after injecting putrid blood into mice and noting 

 that a large amount killed by direct poisoning, while a very 

 small amount produced disease, says of the first : " No inflam- 

 mation can be observed in the neighborhood of the place of 

 injection. The internal organs are also unaltered. If the 

 blood taken from the right auricle be introduced into another 

 mouse, no effect is produced. Bacteria cannot be found in 

 any of the internal organs, nor in the blood of the heart. An 

 infectious disease has not been induced as the result of the 

 injection. On the other hand, there can be no doubt that 

 the death ef the animal was due to the soluble poison, sepsin, 

 which has been shown by the researches of Bergman, Panum, 

 and various other investigators, to exist in putrid blood. The 

 animal has accordingly died, not from an infectious disease, 

 but from a chemical poison. This supposition is confirmed 

 by the fact that when less fluid is introduced into the animal 

 the symptoms of poisoning are less marked, and are quite 

 absent when one, or at most, two drops are injected. After 

 the use of such a small quantity of blood, mice often remain 

 permanently without any morbid symptoms. But a third of 

 them will become ill after the lapse of about twenty-four 

 hours, during which time they have remained perfectly 

 healthy. The symptoms which are then present are charac- 



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