140 BACTERIOLOGY. 



of resisting the effects of cold. It has been 

 stated that comma bacilli exposed to a tempera- 

 ture of 10 for an hour, and bacilli of anthrax 

 after exposure to a temperature of noC, still 

 retained their vitality. Temperatures over 50 to 

 60 C. destroy most bacteria, but not their spores; 

 spores of anthrax retain their vitality after im- 

 mersion in boiling water, but are destroyed by 

 prolonged boiling. Roughly speaking, all patho- 

 genic bacteria grow best at the temperature of 

 the blood, and non-pathogenic bacteria at the 

 ordinary temperature of the room. 



Effect of movement. Bacteria probably grow 

 best when left undisturbed. Violent agitation of 

 a vessel in which they are growing certainly 

 retards their growth, but a steady movement is 

 stated not to affect it ; at any rate anthrax bacilli 

 grow with enormous rapidity in the blood vessels, in 

 spite of the circulation. 



Effect of compressed air. Paul Bert maintained 

 that a pressure of twenty-three to twenty-four 

 atmospheres stopped all development of putre- 

 factive bacteria. Oxygen, under a pressure of five 

 or six atmospheres, is stated to stop their growth. 

 Other observers have, however, obtained different 

 results. 



Effect of gases. Hydrogen and carbonic acid are 

 stated to stop the movements of the motile bacteria. 

 Chloroform is believed to arrest the changes brought 

 about by the zymogenic species. 



