144 BACTERIOLOGY. 



animals. These poisonous alkaloids, ptomaines, 

 produce a septic poisoning, which must be dis- 

 tinguished from septic infection. The effects of 

 septic poisoning depend on the dose, whereas the 

 effects of septic infection are, to a certain extent, 

 independent of the dose. A small quantity of a 

 septic poison may produce only transient effects, 

 and a relatively large quantity may be necessary 

 to produce vomiting, rigors, and death. Septic 

 infection, on the other hand, may result equally 

 from a small dose, because the poison introduced 

 is a living organism which is capable of propaga- 

 tion and multiplication. Our knowledge of these 

 alkaloids is greatly attributable to the researches of 

 Selmi, Gautier, and also Brieger and others. Brieger 

 has isolated ptomaines from the human cadaver, 

 putrid meat, fish, and cheese. These substances 

 cadaverin, putrescin, saprin, peptotoxin, and many 

 others vary in their toxic properties. 



Pathogenic bacteria are those which are genetically 

 related to disease. Many organisms have been 

 supposed to be pathogenic, or have been described 

 in connection with diseases, which are only sapro- 

 phytic associates. By the latter we mean organisms 

 which feed upon dead organic matter. Such are 

 many forms which are found on the skin, in the 

 intestinal canal, and, according to Klein, in the 

 liver and internal organs, where the tissues have 

 lost their vitality, and the organisms, through some 

 lesion, have been carried into the circulation. 



