PROTEUS VULGARIS. 



381 



a narrow zone of bacteria two or three layers in thickness, Superficial 

 this zone being at the outer part surrounded by a single cc 

 layer of bacteria. From the latter tongue-like branches 

 and projections pass outwards, and these projections, 

 which consist of groups of rods and threads, constantly 

 vary their position, become separated, and pass with a 

 slow gliding movement over the surface of the gelatine, 

 forming isolated islands and anastomosing threads ; after 

 some time and at a favourable temperature (20 to 22 C.) 



Fig. 106. Swarming islands of proteus vulgaris (Hauser) X 285. 



active changes of situation can be seen to be going on in 

 all these islands and threads, and circular movements 

 are more especially evident. Gradually the whole sur- 

 face of the gelatine becomes covered with wandering 

 colonies ; from that point rapidly progressing liquefac- 

 tion occurs, which, after 24 to 48 hours, affects the 

 whole surface to a depth of about 1 mm. At the same 

 time there is a foul smell and a marked alkaline reaction. 



While these phenomena are observed in the superficial Characters of 

 colonies, a ray-like arrangement, composed of chains of placed^ y 

 rods, is formed around the deeper zooglsea masses ; colomes - 

 these chains as a rule run outwards in a radiating 

 manner, and show a peculiar movement in that they 

 often shoot out and then again retract. They gradually 

 bore more deeply into the gelatine, the ray arrangement 

 becomes more markedly developed, and the area of the 



