540 BACTERIOLOGY. 



shorter and longer forms may also be seen, even grow- 

 ing out into flexible filaments, which are sometimes 

 more or less wavy or twisted like braids of hair. The 

 bacillus does not form spores, and stains readily with 

 f uchsin or gentian-violet. 



Biological Characters. An aerobic, facultative anaer- 

 obic, liquefying, motile bacillus. Grows rapidly in 

 the usual culture media at the room-temperature. 



Growth on Gelatin. The growth upon gelatin plates 

 containing 5 per cent, of gelatin is very characteristic. 

 At the end of ten or twelve hours at room-tem- 

 perature small round depressions in the gelatin are 

 observed, which contain liquefied gelatin and a whitish 

 mass consisting of bacilli in the centre. Under a low- 

 power lens these depressions are seen to be surrounded 

 by a radiating zone composed of two or more layers, 

 outside of which is a zone of a single layer, from which 

 amoeba-like processes extend upon the surface of the 

 gelatin. These processes are constantly undergoing 

 changes in their form and position. The young colo- 

 nies deep down in the gelatin are somewhat more 

 compact, and rounded or humpbacked; later they 

 are covered with soft down; then they form irregular, 

 radiating masses and simulate the superficial colonies. 

 But it is difficult to describe all the forms which the 

 proteus vulgaris takes on in all the stages of its growth 

 on gelatin plates. When the consistency of the medium 

 is more solid, as in 10 per cent, gelatin, the liquefac- 

 tion and migration of surface colonies are more or less 

 retarded. In gelatin stick cultures the growth is less 

 characteristic liquefaction takes place rapidly along 

 the line of puncture, and soon the entire contents of 

 the tube are liquefied. 



