634 POPULAR SCIENCE MONTHLY. 



the milk, although it will keep some time, is not indefinitely pre- 

 served. The common method used is heating with superheated 

 steam. The milk is placed in bottles of special device, holding 

 about a pint or a quart, and are placed, hundreds at a time, in a 

 large chamber which can be hermetically sealed and then filled 

 with steam under pressure. Here the temperature rises to 102 to 

 106 C. (216 to 220 F.), and is retained here for some little time. 

 This high heat is supposed to kill all the living bacteria that may 

 be in the milk, even the resisting spores being commonly destroyed. 

 "While the milk is still in this apparatus, and before the chamber is 

 opened, the bottles are sealed by a mechanical contrivance and then 

 allowed to cool. After this they are taken out of the sterilizer, and 

 are ready for distribution. The milk thus treated is sometimes pure 

 white, although frequently it has acquired a brownish color, which 

 is not enticing to one accustomed to ordinary milk. Moreover, it 

 has a taste of cooked milk, which is to some people very unpleasant. 

 But when the method is successful the milk contains no living bac- 

 teria, and may now be kept indefinitely without further change. It 

 may be shipped to all parts of the world, and whenever opened it 

 will be found still sweet. The process is evidently equivalent to 

 the canning of fruit or meat, only more difficult because the milk 

 commonly contains many resisting spores. 



Such sterilized milk can be bought almost anywhere in Europe, 

 and there is undoubtedly a growing demand for it. Where this or 

 other sterilized milk is used it is claimed that very favorable results 

 follow. Careful statistics have been collected as_to the number 

 of deaths among infants from diarrhoeal diseases, and it is found 

 that in some cities the deaths from infants fed upon raw milk are 

 nearly three times as great as among those fed upon sterilized milk. 

 Of course, no typhoid epidemics can ever be traced to such milk, 

 and in general its use seems to meet with decided favor. 



There are, however, some serious objections to this method of 

 treating milk, which have been and probably will continue to be 

 sufficient to prevent its wide extension. The first is that such milk 

 appears to be slightly less digestible than raw milk. Over this 

 matter, however, there has been and still is a great diversity of 

 opinion, and many claim that there is really no difference in the 

 digestibility. It is a matter of comparatively little importance, 

 however, at least for adults and healthy children, for the sterilized 

 milk can be digested, and the slight difference in ease of digestion 

 probably has little significance unless it be for weakly individuals. 

 Secondly, the taste of the sterilized milk is that of boiled milk, and 

 this is rather unpleasant to most people. Probably a majority of 

 our people, if called upon to drink sterilized milk or none at all, 



