INFLUENCE OF TEMPERATURE. 75 



61. Influence of Temperature. 



The ordinary conceptions with regard to the favourable or 

 prejudicial influence of certain temperatures on organic life cannot 

 be applied, without modification, to bacteria, and this is particularly 

 the case with respect to the effects of cold. 



J. FORSTER (I.) was the first to find (in 1887) that there are 

 species of bacteria which at a temperature of o C. are not only 

 alive, but actually reproductive. This report is based on a luminous 

 bacterium isolated by him from the surface of a phosphorescent 

 salt-water fish. B. FISCHER (I.) next discovered fourteen other 

 species, some in sea-water, others in the soil, all of which were 

 very reproductive at o C. Returning to the subject, J. FORSTER 

 (II.) then examined more narrowly the natural habitat of similar 

 bacteria and found that 



Commercial milk contained up to 1000 per i c.c. 

 Drain water contained up to 2000 per i c.c. 

 Garden soil contained up to 140,000 per i gram. 

 Street mud an innumerable quantity per i gram. 



MIQUEL (I.), by keeping a sample of sea- water at o C., found 

 that an initial number of 150 germs per i c.c. increased to 520 in 

 twenty-four hours and to 1750 in four days. These facts indicate 

 that glacier water, hail, and snow may also contain bacteria. 

 Quantitative researches on this point have been carried out by 



L. SCHMELCK (I.), 0. BUJWID (I.), W. FoUTIN (I.), Tfl. JANOWSKI (I.), 



and especially P. MIQUEL (I.). 



The resistance of bacteria to low temperatures extends con- 

 siderably below zero Centigrade, FRISCH (I.) having shown that 

 some species will bear cooling down to 110 C. for a short time 

 without injury. R. PICTET and E. YUNG (I.) found that bacteria 

 (species unknown) could be kept at 70 C. for 108 hours and at 

 -130 C. for twenty hours without succumbing; certain (un- 

 named) species even withstanding the effects of a short exposure 

 to 213 C. in solidified oxygen. These facts are not merely of 

 general biological interest, but also, at the same time, important 

 as regards the question of the suitable treatment of stored food- 

 stuffs. This will be discussed in a subsequent paragraph. 



Antithetical to these cold-loving bacteria is the Bacillus ther- 

 mophilus, discovered by MIQUEL (II.), which thrives and repro- 

 duces with great activity at 70 C., a temperature which instantly 

 kills animal cells, coagulates egg albumin and blood serum, and 

 produces painful burns on the skin. When kept at 50 C. this 

 aerobic bacillus occurs as short rods, about i /A in thickness, which 

 become longer as the temperature rises, threads beginning to 

 form at 60 C. and constituting at 70 C. the sole occupants of 

 the field. The lowest limit of temperature at which development 

 of this organism can be observed is about 42 C. ; above 72 C. 



