XXI] PATHOGENIC ORGANISMS 547 



— he left the seeds for many hours and days in the infusion 

 — it is not to be wondered at that this would bear a con- 

 siderable amount of dilution, and still retain its poisonous 

 properties. From all this we see, then, that the jequirity 

 bacillus /«r« has nothing to do with the poisonous principle 

 of the jequirity seeds, but that this principle is a chemical 

 ferment in some respects (in its inability to withstand boiling) 

 similar to the pepsin ferment. 



Messrs. Warden and Waddell published in Calcutta 

 during 1886 a most valuable memoir, detailing a large 

 number of observations on the jequirity poison, which are 

 in complete harmony with my own observations. They 

 have definitely proved that the active principle is a proteid 

 — abrin — closely allied to native albumen ; that its action is 

 similar to that of a soluble ferment, that it can be isolated, 

 and that it is contained not only in the seeds but also in 

 the root and stem of Abrus precatorius. 



Sidney Martin has also published important facts con- 

 cerning the chemical nature of abrin, according to him it is 

 allied to an albumose. Ehrlich considers it as a tox- 

 albumin and he has shown the remarkable fact that by small 

 and repeated doses of abrin an animal (rabbit) can be 

 immunised against a fatal dose {see later). 



The second question which we put, viz. : Can a true 

 saprophyte become pathogenic in the animal body owing to 

 conditions within the animal ? is more difficult to answer, 

 and is intimately bound up with the further question, viz. : 

 What is and what is not a specific or pathogenic microbe ? 



Specific or Fat/wgenic Microbes. — If under a specific microbe 

 is understood a microbe that is connected with and is the 

 causa causans of a definite infectious disease belonging to 

 the group of communicable diseases occurring in nature and 

 affecting man or animal or both, then the number of 



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