NOT DESCRIBED IN PREVIOUS SECTIONS. 401 



rapidly as Proteus vulgaris. Upon gelatin plates, at the end of twelve 

 hours, superficial colonies of two to three millimetres in diameter are formed ; 

 under a low power these appear finely granular and brownish in color, and 

 have an irregular outline; outgrowths from the margin extend in varkms 

 directions and form new colonies, which may be attached for a time by a 

 long and slender thread consisting of bacilli. The movement of these new 

 colonies is not as pronounced as in the case of the preceding species, and 



FIG. 157. " Swarming islands " of Proteus mirabilis, from a gelatin culture, x 285. (Hauser.) 



they are characterized by the presence of numerous distorted bacilli invo- 

 lution forms. The deep colonies form spiral zoogloea masses. 



In gelatin stick cultures the whole surface is first covered with threads 

 and islands of bacilli, which after a time form an anastomosing network, and 

 finally a confluent layer which at the end of forty-eight hours is rather thick, 



FIG. 157. Spiral zoogloea from a culture of Proteus mirabilis. X 95. (Hauser.) 



with a moist, shining surface and grayish color, and appears to be perforated 

 with numerous small, sieve-like openings. These thinner and transparent 

 places disappear after a time, and at the end of two or three days liquefac- 

 tion of the gelatin commences; complete liquefaction does not occur until 

 the fifth or sixth day, or even later. Along the line of puncture finely gran- 

 ular colonies are first formed, from which long threads are given off, which 

 form after a short time a tolerably broad zone of threads and spiral zoogloea 



masses. 



39 



