460 CITY MILK SUPPLY 



of their bacteriological examinations of milk the coincidence between the 

 high bacterial counts of summer and the high total infant mortality of 

 that season was noted and further analysis showed that the high death 

 rate of infants from intestinal disease and these high counts also corre- 

 sponded. So, it was concluded that dirty milk was one of the causes of 

 this sort of trouble in babies. 



Tp determine the injurious effect of bacteria in milk on infants more 

 exactly and if possible to discover what bacteria were the harmful ones, 

 Park and Holt from 1901 to 1904 made an extensive study of the problem 

 in certain hospitals and tenement districts of New York City. Their 

 conclusions in part are : 



"1. During cool weather neither the mortality nor the health of the infants 

 observed in the investigation was appreciably affected by the quality of the mar- 

 ket milk or by the number of bacteria which it contained. 



"2. During hot weather, when the resistance of the children was lowered, 

 the kind of milk taken influenced both the amount of illness and the mortality ; 

 those who took condensed milk and cheap store milk did the worst, and those 

 who received breast milk, pure bottled milk and modified milk did the best. The 

 effect of bacterial contamination was very marked when the milk was taken 

 without previous heating; but, unless the contamination was very excessive, 

 only slight when heating was employed shortly before feeding. 



"3. The number of bacteria which may accumulate before milk becomes 

 noticeably harmful to the average infant in summer differs with the nature of 

 the bacteria present, the age of the milk, and the temperature at which it has 

 been kept. When milk is taken raw, the fewer the bacteria present the better 

 are the results. Of the usual varieties, over 1,000,000 bacteria per cubic centi- 

 meter are certainly deleterious to the average infant. However, many infants 

 take such milk without apparently harmful results. Heat of 145F. for 30 min. 

 or of 170F. for a shorter period not only destroys most of the bacteria present, but 

 apparently some of their poisonous products. No harm from the bacteria pre- 

 viously existing in recently heated milk was noticed in these observations unless 

 they had amounted to many millions, but in such numbers they were decidedly 

 deleterious. 



"4. When milk of average quality was fed, sterilized and raw, those infants 

 who had received milk previously heated did, on the average, much better in 

 warm weather than those who received it raw. The difference was so quickly 

 manifest and so marked that there could be no mistaking of the results. 



"5. No special varieties of bacteria were found in unheated milk which 

 seemed to have any special importance in relation to the summer diarrheas of 

 children. A few cases of acute indigestion were seen immediately following the 

 use of pasteurized milk more than 36 hr. old. Samples of such milk were found 

 to contain more than 1,000,000 bacteria per cubic centimeter, mostly spore- 

 bearing varieties. The deleterious effects, though striking, were neither serious 

 nor lasting. 



"6. After the first 12 months of life infants are less and less affected by the 

 bacteria in milk derived from healthy cattle and the air. According to these 



