52 



ELEMENTS OF WATER BACTERIOLOGY. 



C. coli. 

 (2) Gelatin-stab. — Quick growth 

 on the surface and along the line 

 of inoculation. 



(3) Gelatin-slope. — Thick broad 

 grayish-white growth with a cre- 

 nated margin. 



(4) Witte's Peptone and Salt 

 Solution. — Indol produced. 



(5) Milk. — Coagulated. 



(6) Litmus-whey, one week at 



37 C. Acid produced, usually 



requiring from 20 to 40 per cent of 



N 



— alkali to neutralize it. 



10 



(7) Neutral-red Glucose-agar. — 

 Marked green fluorescence. 



(8) Glucose-gelatin and Lac- 

 tose-gelatin Shake Cultures, and 

 Glucose-agar-stab. — Marked gas 

 formation. 



(9) Gelatin, 25 per cent, incu- 

 bated at 37 C— Thick film 

 appears on the surface. 



(10) Potato. — As a rule, a thick 

 yellowish-brown growth. 



(n) Proskauer and Capaldi's 

 Media. No. I, after twenty hours 

 growth, medium acid. No. II, 

 Growth, medium neutral or faintly 

 alkaline. 



(12) Nitrate-broth. — Nitrate re- 

 duced to nitrite. 



(13) Microscopical Appear- 

 ances. — A small bacillus often like 

 a coccus, not motile as a rule. 



(14) Flagella. — Usually 1 to 3, 

 short and brittle; sometimes 8 to 

 12, long and wavy. 



B. typhi. 



(2) Slow growth on the surface 

 like the colonies; along the line of 

 inoculation the growth is much 

 thinner, and often ends below in a 

 few white points consisting of dis-~ 

 crete colonies. 



(3) Thin narrow grayish-white 

 growth, crenated margin not 

 marked as in B. coli. 



(4) No formation of indol. 



(5) Unchanged after a month. 



(6) Very small amount of acid 



produced, requiring not more than 



N 

 6 per cent of — alkali to neutralize 

 10 



it. 



(7) No change. 



(8) No gas formation. 



(9) No film appears on the sur- 

 face, but a general growth takes 

 place throughout the tube. 



(10) Thin transparent growth 

 hardly visible to the naked eye. 



(n) No. I, no growth or change 

 in the reaction of the medium. 

 No. II, Growth, medium acid. 



(12) Reduction of nitrate not so 

 marked. 



(13) Usually longer than B. 

 coli; highly motile, with * quick 

 serpent-like movement. 



(14) Usually 8 to 12, long and 

 wavy. 



