142 A MANUAL OF BACTERIOLOGY 



Bacterium phosphorescens. The cells of this mi- 

 crobe are almost circular, being from 1*3 to 1*9 /JL 

 long, and l l l to 1*7 p broad; each cell is motile, 

 and surrounded by a gelatinous membrane. It is 

 readily cultivated on fish broth containing a small 

 quantity of peptone ; it grows slowly at the ordinary 

 temperature in peptonised gelatine, or in peptonised 

 gelatine containing 2 per cent, of glucose, but only 

 at the surface, and the property of emitting light 

 depends on the presence of oxygen. 1 It also grows 

 well in 2, 3, and 4 per cent, solutions of sea-salt, 

 containing 0'25 per cent, of peptones. On shaking, 

 the phosphorescence becomes intensified, but on 

 cooling to C. its intensity is somewhat dimin- 

 ished. The phosphorescence disappears when the 

 solution is heated to 35 C. for a few minutes, but 

 re-appears on cooling; it is, however, completely 

 destroyed by heating at 35 C. for fifteen minutes. 



After two or three weeks the culture solutions 

 become yellowish, and gradually lose their phos- 

 phorescence; after several weeks phosphorescence 

 ceases entirely, but the microbes do not die. The 

 phosphorescence is most probably caused by ferment 

 action in the presence of oxygen. This microbe 

 forms colonies on the surface of agar-agar, gelatine, 

 and potatoes, and also grows in urine and milk. 



Bacterium P/%m'. This microbe is the most 

 phosphorescent of all the light-emitting bacteria. 

 It is distinguished from the preceding form by not 

 emitting light with peptone and maltose, but it 



1 See Hjelt's General Organic Chemistry (English translation), 

 p. 94. 



