252 MICEO-ORGANISMS IN WATER 



vessel were kept in continuous and somewhat rapid 

 movement, than in those left at rest/ 



Behaviour of bacteria in ice. — Closely connected with 

 the subject of bacterial multiplication, to which this- 

 chapter has been mainly devoted, is that of the be- 

 haviour of bacteria in ice, regarding which a consider- 

 able amount of information has already been obtained. 

 Thus, some exceedingly instructive investigations on 

 the behaviour of pathogenic and other micro-organisms 

 in artificially prepared ice have been made by 

 Prudden,^ The bacteria used in these experiments 

 were the B. prodigiosus (see p. 140), Proteus vulgaris- 

 (see p. 420), a liquefying bacillus obtained from water,. 

 Staphylococcus pyogenes aureus (see p. 498), a fluores- 

 cent bacillus and the typhoid bacillus (see p. 410). 

 These organisms were inoculated severally into samples 

 of sterilised water, which were then exposed by means- 

 of a freezing-machine to a temperature of 14-30'' 

 Fahrenheit for a period of 103 days. It was found that 

 the number of B. prodigiosus originally present in the 

 sterile water diminished from 6,300 per c.c. in 4 days to- 

 8,000 ; in 37 days the numbers had fallen to 22, and at 

 the end of 51 days none were discoverable. The Pro- 

 teus vulgaris, starting with 8,300 per c.c, in 18 daj's 

 was reduced to 88, and after 51 days none were dis- 

 coverable. The liquefying bacillus from water, being- 

 present in such large numbers as 800,000 per c.c, in 

 4 days was entirely destroyed. Staphylococcus pyo- 

 genes aureus, inoculated into water from a fresh agar- 

 agar culture, and initially present in uncountable 

 numbers in the c.c, was still present to the number of^ 

 50,000 per c.c after 66 days, whilst when taken from 



^ ' On Bacteria in Ice and their relations to Disease,' New York 

 Medical Eecord, 1887, March 26 and April 2 ; Centralhlatt filr BaMerio- 

 logie, vol. i.p. 650, 1887. 



