426 A MANUAL OF BACTERIOLOGY 



and this may exceptionally occur. Thus Horrocks, 1 in 

 some experiments performed at Gibraltar, showed that 

 specific bacteria present in sewage may be ejected into 

 the air of ventilating pipes, inspection chambers, drains 

 and sewers by (a) the bursting of bubbles at the surface 

 of the sewage, (b) the separation of dried particles from 

 the walls of pipes, chambers and sewers, and probably by 

 (c) the ejection of minute droplets from flowing sewage. 

 But the principal action of sewer-gas probably is to lower 

 vitality and increase susceptibility, for Alessi found that 

 animals exposed to drain emanations are at first more 

 susceptible to infection, but after a month or so acquire 

 tolerance and are no more susceptible than animals 

 kept under ordinary conditions. Exposure to the gaseous 

 emanations from putrefying matter is stated by Trillat 

 to increase the virulence of pathogenic bacteria. There 

 is no evidence that sewer-men or those employed at 

 sewage-works suffer from ill-health. 



Action of heat, germicides, etc. The B. typhosus in broth 

 culture is killed by a temperature of 53-54 C. in half an 

 hour, and of 56-60 C. in ten minutes. It is readily 

 destroyed by antiseptics. (See table, Chapter XXII.) 



Semple and Grieg (loc. cit.) found bright sunlight to be 

 germicidal in from two to six hours. 



Wines and spirits have some germicidal action on the 

 typhoid bacillus. Champagne destroys the bacillus in 

 ten minutes, white wines in fifteen to twenty minutes, 

 red wines in thirty minutes or thereabouts. If diluted 

 with water the germicidal action takes much longer to 

 accomplish, and the acidity, not the alcohol content, seems 

 to be the determining factor. 2 Spirits, such as whisky or 

 brandy, if diluted with not more than one to two times 

 the volume of water, kill in ten to twenty minutes. 



1 Journ. Roy. San. Inst., May, 1907, p. 176. 



2 Sabrazes and Marcandier, Ann. de Vlnst. Pasteur, 1907. 



