324 PHARMACEUTICAL BACTERIOLOGY 



spitting habit of the adult male is largely due to the use of tobacco, espe- 

 cially chewing tobacco. While it is not possible to discontinue spitting 

 altogether, it can certainly be greatly teduced. Women rarely spit in 

 pubUc and men can, if they will, also discontinue the nasty habit. 



A most serious defect in places of habitation is the lack of pure air, as in 

 small bed-roorns, in the Pullman sleepers, in sweat shops, in factories, in 

 school-rooms. Next to the crowded sweat shops in our large cities, the 

 lower berth in the American Pullman car, is most unsuitable for human 

 habitation. Rooms for living purposes, sleeping purposes, for factory use, 

 office use, etc., etc., should not only be large enough^ but there should 

 be adequate provision to renew the air constantly, no matter how warm or 

 how cold it may be. We need a thorough sanitary supervision of all 

 building construction, whether private home, school, factory, sleeping car, 

 office, or street car. There is plenty of pure air and every individual 

 should have an ample supply, for pure air is one of the most potent factors 

 in preventive medicine. 



c. Heat. — Heat is one of the best disinfectants known. Dry and moist 

 heat are used, both of which have been sufficiently treated in the preceding 

 chapters. Mere dryness is in itself a germ destroyer. Microbes require 

 moisture for their growth. Most bacteria (vegetative cells, not spores) suc- 

 cumb in a dry atmosphere in a comparatively short time, several hours to 

 several days. The spores may, however, survive dryness for many months. 



The dry-air temperature usually employed for germicidal purposes, 

 ranges from 140° C. to 170° C, acting for one hour or longer. A dry heat 

 of 145° C. acting for one hour is sufficient to kill all bacteria, including the 

 spores. Temperatures used for purposes of disinfection and sterilization 

 range from 55° C. to 1 20° C. 55 ° to 75° C. is usually employed in the pasteuri- 

 zation of milk and in sterilizing sera, vaccines, certain culture media (as 

 egg albumen, blood serum), etc. Moist heat of 100° C. in the form of cir- 

 culating steam vapor is much used. To obtain a moist temperature above 

 100° C, an autoclave is necessary, or liquids may be employed which boil 

 at a temperature higher than 100° C. as cumene, oils, etc. 



d. Cold. — Cold, 10° C. and lower, has decided antiseptic properties, that 

 is, it checks bacterial growth and activity very effectually, as has already 

 been explained. Prolonged freezing is, however, necessary to kill bacteria. 

 Cold may therefore be considered a most excellent check upon bacterial 

 activity, but it is a very poor germicide. Cold is a universally recognized 

 and an extensively used food preservative, due to its checking influence 

 upon bacterial growth. 



e. Agitation. — The agitation of gases and liquids reduces the bacterial 

 activity therein. Still waters become stagnant but running waters do not, 

 in the comparative sense, due in part to the difference in the oxygen con- 



