640 PATHOGENIC MICROORGANISMS 



water media or on pep ton waters containing sugars. On the Hiss 

 semi-solid tube-medium Bacillus fecalis alkaligenes, while clouding 

 the medium throughout, grows most heavily on the surface, where, 

 eventually, it forms a pellicle, 



BACILLI OF THE PROTEUS GROUP 



There are a great many other organisms which are similar to the 

 Colon Bacillus in general appearance and superficial morphological and 

 cultural characteristics, and which are found frequently associated with 

 it in feces, water and sewage. It will be important for this reason to 

 speak of them briefly. The most important of these is the Proteus 

 Group, which is sharply separable from the Colon and allied bacteria 

 by its gelatin liquefaction. 



The bacilli of this group have little pathological interest, but are 

 important because of the frequency with which they are encountered in 

 routine bacteriological work. They may confuse the inexperienced 

 because of a superficial similarity to bacilli of the colon-typhoid group. 

 In form they may be short and plump or long and slender, staining easily 

 with anilin dyes and decolorizing with Gram's method. They are 

 actively motile and possess many flagella. Individuals stain irregularly, 

 often showing unstained areas near the center. The so-called Bacillus 

 proteus vulgaris described by Hauser 22 in 1885 is the type of the group. 



Bacilli of this group are widely distributed, being found in water, 

 soil, air, and wherever putrefaction takes place. In fact, proteus is one 

 of the true putrefactive bacteria possessing the power to cause the cleav- 

 age of proteins into their simplest radicles. 



Bacillus proteus vulgaris grows best at temperatures at or about 

 25 C. and develops upon the simplest media. It is a facultative 

 anaerobe and forms no spores. In broth, it produces rapid clouding with 

 a pellicle and the formation of a mucoid sediment. 



In gelatin, the colonies are characteristically irregular, giving the 

 name to this group. 



Gelatin is Rapidly Liquefied. Liquefaction, however, is diminished 

 or even inhibited under anaerobic conditions. 



On agar and other solid media, as well as upon gelatin before lique- 

 faction has taken place, characteristic colonies are produced. From 

 the central flat, grayish-white colony nucleus, numerous irregular 

 streamers grow out over the surrounding media, giving the colony a 

 stellate appearance. On potato, it forms a dirty, yellowish growth. 



22 Hauser, "Ueber Faulniss-Bakt., ' ' Leipzig, 1885. 



