QUANTITATIVE BACTERIOLOGICAL ANALYSIS. 19 



Tiemann and Gartner made many experiments with pure cul- 

 tures. Their results are given in the following tables : 



Number of bacteria hi 1 c.c. 

 Flace from which after 

 ORGANISM. the specimen * 



was taken. 1 day. 2 days. 3 days. 4 days. 



A motile bacillus produc- rl c.m. under j 

 mg green pigment. the surface. J 



The column of fluid was-l F ^ 173,000 232,000 r 286,000 384,000 



20 c.m. high and main- 1 -I (after shaking) 



tained at 18 to 20 C. [ >m ' J I 288,000 368,000 



1 c.m. under \ 25,700 

 the surface./ 28,200 



From the 1 25,200". , ,, 



Kafter shaking, 22,000). 

 bottom. ) no nnn ' v 



Noil-motile coccus ob- 

 tained from the air. 



Column of fluid 20 c.m. 

 high. 



In order to test the effect of a greater depth of fluid, a glass 

 tube 60 c.m. high and 2'5 c.m. wide was filled with sterilised 

 service water containing 11,000 motile bacilli per c.c. and kept 

 at 50 C. for ten days. The following results were obtained : 



C 910.000 per c.c. 

 1 c.m. under the surface { g ^ m ^ 



Direct from the bottom { JJJjJjj " 



Next a glass tube 54 c.m. high and 2 '5 c.m. wide was filled 

 with sterilised water containing 13,000 white micrococci per c.c. ; 

 the results were as follows : 



After 10 days After 20 days After 30 days 



at 5 C. at 12 C. at 10 C. 



1 c.m. under the surface, j Q Q 



bacteria per c.c. J 



From the bottom, j ^ Q Q 

 bacteria per c.c. J 



These experiments appeared to show that neither motile nor 

 non-motile micro-organisms sank to the bottom. 



Scheurlen placed in a tube, 17 c.m. high, suspensions of B. 

 typhosus, B. megaterium, Proteus vulgaris, Proteus mirabilis, 

 and Sp. Cholerae Asiaticse. At the end of four days he found 

 that the three first microbes had in great part sunk to the 

 bottom, whilst the last two appeared to remain equally distri- 

 buted through the water. 



It is possible that oxygen, being necessary for the maintenance 

 of vitality of aerobic organisms, exercises an influence on the 



