THE CHEMISTRY OF BACTEBIA. 89 



Yiew was largely based upon analogy. Thus, it is well 

 known that many of the poisonous higher plants owe their 

 injurious action to the presence of the so-called vegetable 

 alkaloids. Strychnin, morphin, atropin, nicotin, etc., are 

 examples of this kind. It soon became evident, however, 

 that the ptoma'ins could not be considered as the chief 

 poisons elaborated by bacteria. In the first place, the 

 amount of ptomains present in a filtered bacterial liquid was 

 too small to account for the intensely poisonous action of 

 such a liquid. Moreover, certain bacteria, like the diph- 

 theria bacillus, do not give rise to ptomains. Clearly, there- 

 fore, the real weapon possessed by bacteria is of a different 

 chemical nature. 



It has already been shown that the specific poisons of 

 the pathogenic bacteria are known as toxins. They are 

 certainly not basic substances or ptomains, and they are 

 not protein compounds. The ptomains, consequently, are 

 of only secondary importance as factors in the production 

 of disease. They are simple, waste-products which result 

 from the breaking down of albuminous matter. 



Alkalis. — Many bacteria impart an alkaline reaction to 

 the medium in which they grow. As a rule, certain nitro- 

 genous substances must be present in order that alkaline 

 products may form. The protein compounds are of this 

 kind. In the bacterial decomposition of urine the urea 

 is decomposed into ammonia and carbonic acid. Ammonia is 

 the most common alkali made by bacteria. It represents 

 the final, inorganic form to which the nitrogen of dead 

 protoplasm is eventually reduced. An alkaline reaction 

 may result from the oxidation of sodium acetate and 

 .similar salts. In such instances sodium carbonate would 

 form. 



Certain organic derivatives of ammonia are frequently 

 met with. These are known as amines and result from 

 the introduction of an organic group into the ammonia 



