10 MICROBES AND TOXINS 



transform the urea, by means of a urease which they secrete, 

 into carbonate of ammonia. Hippuric acid is transformed 

 into benzoic acid and glycocoll, and finally into ammonia. 



The putrefactions of albuminous materials in nature are 

 never simple, that is to say carbohydrates almost always 

 accompany the proteins ; even meat contains a little sugar. 

 Putrefactions therefore are almost always mixed fermentations. 



Pasteur thought that all putrefaction was the work of 

 anaerobes. He discovered the vibrion septique, an anaerobic 

 bacillus capable of decomposing proteins. Later, the 

 anaerobes were neglected and it was thought that various 

 aerobes, in particular Proteus^ were the principal agents of 

 putrefaction. But after the study of fetid suppurations had 

 drawn attention to the presence of anaerobes (Veillon), the 

 idea rose again that they too must play a part in putrefaction, 

 and the methodical study of this subject was recommenced, 

 chemical analysis going hand in hand with bacteriological 

 examination. 



In their experiments, Tissier and Martelly followed 

 for months the events which took place in flasks into which 

 meat had been put and allowed to putrefy either with or 

 without access of air. Meat taken from the slaughter-house as 

 fresh as possible contains all the germs necessary and 

 sufficient for putrefaction, and, as it contains carbohydrates, it 

 is a mixed putrefaction which occurs. 



There are two phases. In the first the sugar and the 

 proteins are attacked by mixed ferments, that is to say, by 

 microbes which decompose at the same time both proteins and 

 sugar, proteolytic and saccharolytic (peptolytic is the term 

 applied to the ferments which attack protein only after 

 its reduction to peptone). In the second phase the protein 

 and its products are attacked by ferments which are 

 proteolytic or peptolytic pure and simple, not saccharolytic. 



But between these two phases a critical turning-point occurs: 

 the decomposition of the sugars produces an acidity sufficient 

 to stop putrefaction. The "antagonistic force" which 

 Bienstock observed in his investigations on a putrefactive 



