104 THE ACTION OF ENZYMES 



are rare and not likely to occur in putrefying substances 

 under ordinary conditions. A small number, however, 

 are very widely distributed in nature, and are almost 

 invariably concerned in the destruction of animal and 

 vegetable organic matter. The chief of these are 

 described below. 



i. Bacterium vulgare, L. and N. (Proteus vulgaris, Hauser). 

 An examination of a piece of putrid meat which has been freely 

 exposed to the air reveals the presence of immense numbers of 

 minute bacteria which were formerly spoken of as Bacterium termo. 

 Investigation by Hauser and others showed that these organisms 

 were remarkable in being able to assume very many different 

 growth-forms, occurring sometimes as short rods almost like 

 cocci, and under other conditions as long straight rods or 

 spiral threads. On account of its variability the genus was 

 given the name Proteus, and three more or less distinct forms were 

 described under the names Proteus vulgaris, P. mirabilis, and 

 P. Zcnkeri. More recently these have been grouped together as 

 varieties of the species Bacterium vulgare, L. and N. (Bacillus 

 vulgaris, Mig.). They are very common in putrid flesh, and of 

 frequent occurrence in water contaminated with decomposing 

 animal matter. They are also common inhabitants in the 

 intestines of man and other animals. 



The following are the chief characters of typical Bact. 

 vulgare : 



The organisms are usually slender, very active motile rods, 

 from i to 4 ^ long and .4 to .7 /a. thick. As stated above they may 

 occur as rods 40 / long or as long spiral threads. They 

 generally stain by Gram's method. Spores are not formed. 



Bact. vulgare grows best under aerobic conditions, though 

 it is able to thrive as an anaerobe. From proteins it pro- 

 duces indole and sulphuretted hydrogen, and its cultures in 

 gelatine or bouillon have a foul odour. 



Gelatine. The colonies are at first thin, grey, and semi- 



