ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 499 



appreciable influence was exerted upon the vital properties of bacteria 

 when exposed for 20 hours to the temperature of liquid air ( — 183° C. to 

 — 193° (J.), have recently made experiments which prove that bacteria 

 can be exposed to a temperature of — 190° C. for a period of seven days 

 without any appreciable impairment of their vitality. The organisms 

 used were : — B. typhosus, B. coli communis, B. diphtherise, B. proteus vul- 

 garis, B. acidi lactici, B. anthracis, Sp. cholerse asiat., Staph, py. aureus, 

 B. phosphor escens, a Surcina, a Saccharomyces, and unsterilised milk. 

 Broth emulsions in hermetically sealed fine quill tubing were used. 

 When thawed after the cooling, a microscopical examination was made 

 to discover if any structural changes had taken place. None were de- 

 tected. The subcultures made at the conclusion of the experiment grew 

 well, and no impairment of vitality was noticed. 



The photogenic bacteria grew and emitted light, and the samples of 

 milk became curdled. 



Still later the authors,* with the aid of Prof. Dewar, as in the pre- 

 vious experiments, subjected this same series of bacteria to the tempera- 

 ture of liquid hydrogen, about —250° C, and again the results were 

 nil. 



Organic Matter and Bacteria in Surface Washings of the Soil.t 

 — Dr. A. C. Houston reports on the chemical and bacteriological exami- 

 nation of the washings of soils, with reference to the amount and nature of 

 the organic matter and the number and character of the bacteria con- 

 tained in them. The results obtained in this inquiry clearly show that 

 chemistry cannot be always relied on to detect in a water supply the 

 presence of " flood-water," much less of " flood-water " of objectionable 

 or dangerous sort. Though some of the " soil-waters" would have been 

 condemned on chemical analysis, yet it was found that the " washings " 

 from some soils of unobjectionable character yielded higher results 

 (chemically as regards organic matter) than those known to be grossly 

 and perhaps dangeroxisly polluted. 



The bacteriological results, though not entirely satisfactory, were of 

 an encouraging nature. By taking a sufficiently large bulk (e.g. 1000 ccm.) 

 of the water to be dealt with, and examining the filter brushing suspen- 

 sion, it is possible to demonstrate bacteriologically sewage pollution so 

 minute as to defy detection by chemical means. 



Bacteriological Evidence of Recent Sewage Pollution of Potable 

 Waters.J — The report of Dr. E. Klein and Dr. A. C. Houston on the 

 bacteriological evidence of recent, and therefore dangerous, sewage pol- 

 lution of potable waters, shows that chemistry, as usually applied, is 

 powerless to detect a degree of pollution of water with sewage which, 

 from the point of view of the bacteriologist, would be considered gross 

 in amount. It is also claimed that bacteriology is not only capable of 

 detecting microbes characteristic of sewage under ordinary test condi- 

 tions, but can do so when the sewage pollution is from ten to one 

 hundred times less than that in which the organic matter contributed by 

 the sewage to the water has failed to get recognition by the methods 

 commonly in use by the chemist. 



* English Mechanic, lxxi. (1900) p. 372. 



t Rep. Med. Off. Loc. Gov. Board, 1898-9, pp. 439-66 (2 pis.). 



j Tom. cit., pp. 498-504. 



