436 MICRO-ORGANISMS IN WATER 



BACILLUS CIRCULARS 



! LIQUEFIES GELATINE ' 



Authority. Jordan, A Report on certain Species of Bacteria observed in 

 Sewage, State Board of Health, Massachusetts, 1890, p. 831. 



"Where Found. Found occasionally in the Lawrence tap-water (from the 

 Merrimac River). 



Microscopic Appearance. Long slendsr bacilli about 2 to 5 ^ long and 1 /* 

 broad, with rounded ends ; generally single, but sometimes hanging together in 

 twos and fours. Forms small oval spores in from three to four days in the end 

 of the rod. It is very motile. 



Cultures. 



GELATINE PLATES. Hound brownish colonies are visible in two days. The 

 gelatine is liquefied, and under a low power the rapid motion of the individual 

 bacteria gives to the whole fluid mass the appearance of being in circulation. 

 In three days the movement usually ceases ; the interior looks coarsely granular 

 with flocks of bacteria scattered irregularly here and there. The colonies form 

 a round, deep, even depression, which spreads very slowly ; the contour some- 

 times becomes somewhat lobed instead of being smooth and even. 



GELATINE TUBES. Grows slowly, forming a liquefying cone-like depression, 

 at the bottom of which a deposit collects. It grows well in a slightly acid 

 medium. 



AGAK-AGAR. Forms a very thin translucent surface growth ; grows also in 

 the depth. 



POTATOES.- -Grows slowly and scantily, hardly distinguished in colour from 

 the potato itself. 



MILK. Slowly coagulates the milk with a slight acid reaction. When culti- 

 vated for several months in artificial media it no longer is able to coagulate 

 milk. 



BROTH. Renders it turbid in from three to four days, forming a considerable 

 slimy deposit. No pellicle is formed. 



Remarks. Slowly reduces niti'iiti's to nitrites. (See under B. cloacne.) 



