252 MICRO-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. 1 The bacteria used in these experiments 

 were the B. prodigiosus (see p. 440), 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 

 3,000 ; 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 days 

 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 



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

 Medical Record, 1887, March 26 and April 2 ; CentralUatt fur BaUerio- 

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



