700 BACTERIA IN AIR, SOIL, WATER, AND MILK 



these are by no means sufficient to be of practical importance in the 

 inhibition of bacterial growth. Kept at or about freezing-point, the 

 bacterial contents of milk do not appreciably increase. At higher tem- 

 peratures, however, a rapid propagation of bacteria takes place which, 

 especially during the summer months, speedily leads to enormous num- 

 bers. In a case reported by Park,' where milk, containing at the first 

 examination 30,000 microorganisms per cubic centimeter, was kept 

 at 30° C. (86° F.) for twenty-four hours, the count at the end of this 

 time yielded fourteen billions of bacteria for the same quantity. 



It is of much importance, therefore, that the cleanliness of dairies, 

 of cattle, and in the handling of milk should be reinforced by the utmost 

 care in chilling and icing during shipment and before sale. 



Because of its great importance, especially for the health of the chil- 

 dren in large cities during the summer months, the milk question has, 

 of recent years, received much attention from health officers. In the 

 city of New York, the question has been made the subject of many 

 careful studies by Park ^ and his associates. Commissions, working 

 in Chicago,^ Boston,* and other large towns, have placed the sale of milk 

 under more or less exact bacteriological supervision. Park has de- 

 termined that the milk, as sold in New York stores during the cold 

 weather, not infrequently averages seven hundred and fifty thousand 

 bacteria per cubic centimeter; during the hot summer months, the 

 bacterial contents of similar milk not infrequently average one million 

 and more, for the same quantity.* In consequence of these and other 

 researches, large dairies have introduced bacteriological precautions 

 into their method of milk production. They have attempted the reduc- 

 tion of the bacterial contents of milk by scrupulous cleanliness of the 

 ' barns and of the udders and teats of the cow, by the elimination of dis- 

 eased cattle, by sterilization of the vessels in which the milk is received, 

 and of the hands of the milker; also by the immediate filtering and 

 cooling of the milk and the packing of the milk cans in ice, where 

 they remain until delivered to the consumer. In consequence of such 

 measures, it is possible for cities to be supplied with milk containing no 

 more, and often less, than fifty thousand bacteria to the cubic centimeter. 

 A standard of cleanliness has been established in various towns by the 



1 Park, W. H., "Pathogenic Bacteria," New York, 1905, p. 463. 



2 Park, Jour, of Hygiene, 1, 1901. 



3 Jordan and Heinemann, Rep. of the Civic Federation of Chicago, 1904. 

 * Sedgwick and Batchelder, Bost. Med. and Surg. Jour., 126, 1892. 



' Escherich, Fort. d. Medizin, 16 and 17, 1885. 



