Conditions Prejudicial to Growth of Bacteria 45 



is favored by a change which the staphylococci bring about 

 in the hemoglobin. 



A similar advantageous association has been pointed out 

 by Sanarelli, who found that Bacillus icteroides grows best 

 and retains its vitality longest when grown in company with 

 certain of the molds. 



Rarely, the presence of one species of micro-organism 

 entirely eradicates another. Hankin found that Micro- 

 coccus ghadialli destroyed the typhoid and colon bacilli, 

 and suggested the use of this coccus to purify waters pol- 

 luted with typhoid.* 



An interesting experimental study of the bacterial an- 

 tagonisms with special reference to* the Bacillus typhosus, 

 that the student should read, is by W. D. Frost, and appears 

 in the ''Journal of Infectious Diseases," 1904, i, p. 599. 



Extremes of Temperature. According to Frankel, bac- 

 teria will rarely grow below 16 and above 40 C., but 

 Fliigge has shown that Bacillus subtilis will grow very 

 slowly at 6 C. ; at 12.5 C. fission does not take place 

 oftener than every four or five hours; at 25 C. fission occurs 

 every three-quarters of an hour, and at 30 C. about every 

 half hour. 



A few forms of bacteria grow at very high temperatures 

 (6o-7O C.) and are described as thermophilic. They are 

 found in manure piles and in hot springs. Tsiklinskyf 

 has described two varieties of actinomyces and a mold 

 that he cultivated from earth and found able to grow well 

 at 48-68 C., though not at all at the temperature of the 

 room. 



Most bacteria are killed by temperatures above 6o-75 

 C., but their spores can resist boiling water for some minutes, 

 though killed by dry heat if exposed to 150 C. for an hour 

 or to 175 C. for from five to ten minutes. 



The resistance of low forms of life to low temperatures is 

 most astonishing. Cold inhibits the growth of all bacteria, 

 and immersion in freezing mixtures destroys many. Some 

 adult bacteria and most spores seem capable of resisting 

 almost any degree of cold. Ravenel J exposed anthrax 

 spores to the action of liquid air for three hours, diphtheria 

 bacilli for thirty minutes, typhoid bacilli for sixty minutes, 



* " Brit. Med. Jour.," Aug. 14, 1897, p. 418. 



t " Russ. Archiv f. Path.," etc., Bd. v, June, 1898. 



% " The Medical News," June 10, 1899. 



