70 



THE POPULAR SCIENCE MONTHLY 



being fouglit against poor niilk^ iu many instances with gratifying re- 

 sults. A reduction of infant mortality is usually noted when the public 

 milk supply is improved. Laudable efforts are being made by health 

 authorities in various cities in this country by introducing ordinances, 

 forbidding the selling of milk derived from tuberculous cows, unless the 

 milk is pasteurized. It will, however, require the intelligent and active 

 support of consumers to make these efforts successful. 



Photograph 5 



Milk is secreted from the mammary glands in a sterile condition, 

 that is to say, germs are totall}^ absent. When the milk is discharged 

 from the glands and enters into the cistern — the large reservoir — of the 

 udder, some bacteria gain access; these having invaded the udder from 

 the outside through the teat duct, a small canal in the teats through 

 which the milk is withdrawn. The number of germs entering here is 

 relatively small, however. The large numbers usually found in market 

 milk enter during the process of milking and are the result of multipli- 

 cation during transportation and storage, unless the milk is kept at a 

 temperature below 40° F. ISTo matter how careful the milker may be, 

 some germs are bound to enter. It is therefore necessary to cool the 

 milk rapidly after milking and keep it cold until consumed. We have 

 then to consider chiefly two points in the production and handling of 

 milk, first cleanliness in all manipulations and cleanliness of all utensils, 

 and second rapid cooling and storage or transportation at low tem- 

 peratures. 



Milk is the natural food for all mammals and each species of mam- 

 mal produces a milk of such composition as is most suitable for the 

 young of the species. The- composition of cat's milk differs from that of 



