132 APPLIED BACTERIOLOGY FOR NURSES 



certain disadvantages as well as advantages. If properly 

 done, with fresh milk which is then cooled rapidly, the 

 pathogenic bacteria, such as typhoid and tubercle 

 bacillus, are killed, as are also the lactic acid bacilli, 

 which cause the souring of milk. What remains alive 

 are the spore-bearing varieties. Among them are the 

 putrefactive organisms, but these are present in small 

 numbers only and are unable to develop at low tempera- 

 ture. But it is impossible to tell whether pasteurized 

 milk was really fresh when heated, i. e., it may have 

 been in a tainted condition before pasteurization. 

 Normally, the lactic acid bacilli, by altering the reac- 

 tion of the milk, keep down the growth of putrefactive 

 organisms, but in heated milk the growth of these latter 

 is unchecked, and, unless carefully treated, well cooled, 

 and kept cool, pasteurized milk may have a higher bac- 

 terial count than a good quality raw milk. For this 

 reason the pasteurization of milk supplied by the 

 dealers should be carefully supervised by the public 

 health authorities. 



Home Pasteurization. There is no doubt that home 

 pasteurization of milk has been found of considerable ad- 

 vantage, especially for infants, and several pasteurizers 

 have been put upon the market, the best known among 

 them being those of Arnold and of Freeman. 



A simple milk pasteurizer for home use consists of a 

 tin pail, having a perforated cover and containing a 

 wire basket, into which are fitted eight nursing bottles. 

 The water in the pail is heated to boiling, the wire crate 

 is then lowered until the bottles nearly touch the water. 

 The milk is steamed in the open bottles for ten minutes, 

 then the bottles are corked and steaming is continued 



