THE BIOLOGICAL ACTIVITIES OF BACTERIA 45 



place under anaerobic conditions, that is, in the absence of oxygen, a 

 process usually resulting in incomplete cleavage of the proteid medium ; 

 the latter being used to signify decompositions under aerobic conditions 

 and leading to a more complete splitting, the end-products often being 

 represented by such simple compounds as carbon dioxide, water, and 

 ammonia. In general, the products of putrefaction are largely repre- 

 sented by the amino-acids, leucin and tyrosin, fatty acids, mercaptan, 

 indol, and skatol. The gases generated in such decomposition are largely 

 made up of CO 2 , hydrogen, NH 4 and H 2 S. The coincident presence, 

 furthermore, of the carbohydrate-splitting bacteria and of denitrifying 

 microorganisms renders the actual process of putrefaction a chaos of 

 many activities in which the end-products and by-products are qualita- 

 tively determinable only with much inexactitude, and which com- 

 pletely defies any attempt at quantitative analysis. 



Ptomains. There are certain products, however, resulting from the 

 proteolytic action of bacterial enzymes upon proteids which claim more 

 than a purely chemical interest because of their toxic action upon the 

 animal organism, and their consequent importance as incitants of dis- 

 ease. Pre-eminent among these are the ptomains. The word ptomain 

 (from 7r-w/jta, a dead body) is used to designate organic chemical 

 compounds produced by the action of bacteria, which are basic in char- 

 acter; that is, are able to combine with an acid to form a salt. They 

 should be definitely distinguished from the so-called leucomains, a 

 term employed to designate similar substances formed in the course 

 of proteid metabolism within the animal body, and not bacterial in 

 origin. Both in their basic characters and in their nitrogenous constitu- 

 tion, the ptomains resemble the vegetable alkaloids, and for this reason 

 are sometimes spoken of as "animal alkaloids." 



The ptomains must be sharply distinguished from the bacterial 

 toxins, which are products of the bacterial growth irrespective of the 

 medium in which they are grown, except in so far as this hinders or 

 abets the development of the microorganisms. Thus, toxins may be 

 developed by diphtheria organisms, for instance, in proteid-free media. 

 As will be seen in a subsequent section, the true toxins are comparable 

 to the enzymes themselves, rather than to their cleavage products, rep- 

 resented in this instance by the ptomains. 



A great number of ptomains are chemically Icnown. Many <>f 

 these possess little or no toxicity. Others, however, like putrescin 

 (tetramethylenediamin, C 4 H 12 N 2 ) and cadaverin (C 5 H 14 N 2 ) are very 

 highly poisonous. It is to one or another of these ptomains that most 



