6o MANUAL OF BACTERIOLOGY. 



Pasteurization. — The name pasteurization has been ap- 

 plied to the partial sterilization of substances at a compara- 

 tively low temperature. It is employed particularly for milk. 

 Although the temperature used (63° to 65° C. for 20 to 30 

 minutes) is sufficient to destroy all ordinary pathogenic 

 bacteria, at least in test-tube experiments, and the probability 

 is that where the bacteria are actually brought to the tempera- 

 tures indicated they are destroyed in milk, too great reliance 

 should not be placed upon this mode of sterilization; for, as 

 elsewhere stated, under some circumstances milk may afford 

 a protection for the bacteria, and this should be borne in 

 mind particularly in regard to tuberculosis and typhoid fever. 

 Furthermore, the great majority of the saprophytic bacteria are 

 destroyed, and milk which has been pasteurized will remain un- 

 changed for several days, if kept cool. Its application is 

 principally in the feeding of infants in cases where raw milk 

 causes digestive disturbances. Freeman* has invented a pail 

 of special form for the pasteurization of milk in bottles. This 

 pail is filled with hot water and the bottles are placed in it; it has 

 been found to keep up a temperature of about 75° C. 



The Autoclave. — The autoclave is an-apparatus designed 

 for sterilization by steam under pressure. It was invented in 

 France, but is now used extensively in all parts of the world. 

 Steam generated at the ordinary atmospheric pressure is much 

 less destructive to bacteria, and especially to their spores, than 

 steam in the autoclave at a pressure of an additional one-half 

 to one atmosphere, yj to 15 pounds; the steam then reaches 

 a temperature of about 112° to 120° C. Under these condi- 

 tions culture-media may be sufficiently sterilized in the auto- 

 clave in ten minutes, and at a single sterilization. The auto- 

 clave consists of a metal cylinder with a movable top, which 

 is fastened down tightly during sterilization. It is furnished 



*Uedical Record. July 2, 1892, and August 4, 1894. This pail is sold by 

 James T. Dougherty, 411 West Fifty-ninth Street, New York. 



