PROTEUS-INFECTIONS. 309 



not stain by Gram's method. The proteus thrives equally well 

 at room-temperature and at the temperature of the body. The 

 temperature-optimum is between 20 C. (68 F. ) and 25 C. 

 (77 F. ). The organism does not give rise to spores, and is 

 destroyed by exposure for five minutes to a temperature of 55 

 C. (131 F.). 



Cultural Properties. On gelatin-plates small, round, 

 yellowish colonies form at first, with a dense center and an 

 irregular margin, from which bristle-like processes pass off. 

 Other colonies are bounded by a zone of filaments surrounding 

 the central opaque mass, in part circularly, in part in the most 



Fig. 67. Swarming islands of proteus-bacilli on the surface of gelatin ; X 650 

 (Hauser). 



varied loops and convolutions. Extensive and rapid liquefaction 

 of the gelatin takes place. Into the adjacent nutrient medium 

 extend processes, both straight and tortuous, which frequently 

 are cut off from the mother-area and move about as free islands 

 in the partially liquefied gelatin. These conditions may be espe- 

 cially well observed upon five or six per cent, gelatin. There 

 thus result peculiar figures and designs, to which the proteus 

 owes its name of " bacillus figurans. ' ' 



Gelatine stab-culture is liquefied with exceeding rapidity. 



In agar streak-culture a grayish, moist coating forms. 



On potato a dirty grayish deposit appears. 



Bouillon is rendered homogeneously turbid. 



