46 BIOLOGY AND TECHNIQUE 



cases of so-called meat poisoning (kreatoxismus) , cheese poisoning 

 (tyrotoxismus), or vegetable poisoning (sitotoxismus) are due. 



In each individual case the variety of ptomain resulting from a bac- 

 terial decomposition varies with the individual species of microorganism 

 taking part in the process and with the nature of the proteid upon which 

 its development takes place. 



In breaking down animal excreta, the task of the bacteria is rather 

 a simpler one than when dealing with the cadavers themselves, for here a 

 part of the cleavage has already been carried out either by the destruc- 

 tive processes accompanying metabolism, or by partial decomposition by 

 bacteria begun within the digestive tract. This material outside of the 

 body is further reduced by bacterial enzymes into stUl simpler sub- 

 stances, the nitrogen usually being liberated in the form of ammonia. 

 One example of such an ammoniacal fermentation may be found in 

 the case of the urea fermentation by Micrococcus urese, in which the 

 cleavage of the urea takes place by hydrolysis according to the follow- 

 ing formula: 



(NH^)^ CO + 2H2 O = CO2 + 2NH3 + H2 O 



Similar ammoniacal fermentations are carried out, though perhaps 

 according to less simple formulae, by a large number of microorganisms. 

 Perhaps the most common species which possesses the power is the group 

 represented by B. proteus vulgaris (Hauser). 



From what has been said it follows naturally that, so far, the decom- 

 position of the proteid molecule from its complex structure to ammonia 

 or simple ammonia compounds is an indispensably important function, 

 not only for agriculture, but for the maintenance of all life processes. 

 It is clear, on the other hand, that a further decomposition of ammonia 

 compounds into forms too simple to be utilized by the green plants would 

 be a decidedly harmful activity. And yet this is brought about by the 

 so-called denitrifying bacteria which will be considered in a subsequent 

 section. 



Lab Enzymes. — ^There are a number of ferments produced by bacteria 

 which, although affecting proteids, can not properly be classified with 

 the proteolytic enzymes. These are the so-called coagulases or lab 

 enzymes, which have the power of producing coagulation in liquid pro- 

 teids. Just what the chemical process underlying this coagulation is, 

 is not known. If Hammarsten's * conclusions as to the hydrolytic 



' Hammarsten, "Textbook of Physiol, Chemistry," Translation by Mandel. 



