46 Biology of Bacteria 



and Bacillus prodigiosus for sixty minutes, the temperature 

 of the cultures being reduced to about 140 C., yet in no 

 case was the vegetative capability of all of the bacteria 

 destroyed, and when transferred to fresh culture bouillon 

 they grew normally. His researches corroborate those of 

 Pictet and Yung and others. 



To say that bacteria are not injured by cold is a mistake, 

 as Sedgwick and Winslow* have found that when typhoid 

 bacilli are frozen, the greater number of them are destroyed, 

 and that subsequent development of the frozen cultures 

 takes place from the few surviving organisms. 



Bacteria usually grow best at the temperature of a com- 

 fortably heated room (17 C.), and are not affected by its 

 occasional slight variations. Some, chiefly the pathogenic 

 forms, are not cultivable except at the temperature of the 

 body (37 C.); others, like the tubercle bacillus, grow best 

 at a temperature a little above that of the normal body. 



The Presence of Antiseptics, etc. The presence of 

 chemic agents, especially certain of the mineral salts, in 

 an otherwise perfectly suitable medium may completely 

 inhibit the development of bacteria, and if added to grown 

 cultures in greater concentration, destroy them. Such sub- 

 stances are spoken of as antiseptics in the former, germi- 

 cides or disinfectants in the latter case. Bichlorid of mer- 

 cury and carbolic acid are the most familiar examples of 

 germicides. 



Though these agents are supposed to operate in definite 

 concentrations with almost unvarying result, Trambusti f 

 found it possible to produce a tolerance to a certain amount 

 of bichlorid of mercury by cultivating Friedlander's bacillus 

 upon culture media containing gradually increasing amounts 

 of the salt, until from 1-15,000 which inhibit ordinary cul- 

 tures, it could accommodate itself to 1-2000. 



A thorough knowledge of the biology of bacteria and the 

 conditions prejudicial to their life is of great practical im- 

 portance in enabling one to carry out intelligently clinical 

 precautions such as the sterilization of instruments, surgical 

 dressings, etc., and use sufficiently radical measures for the 

 disinfection of the skin to be incised, as well as of the 

 hands of the operator. 



* " Centralbl. f. Bakt. u. Parasitenk., " etc., May 26, 1900, Bd. 

 xxvn, Nos. 18, 19, p. 684. 



f " Lo Sperimentale, " 1893-4. 



