460 BACTERIA PATHOGENIC TO MAN 



25,000,000 bacteria per cubic centimetre, averaging about 15,000,000, 

 though obtained from healthy cows living under fairly decent conditions 

 and although the milk was kept moderately cool in transit, we find a 

 distinct increase in the amount of diarrhceal diseases. Though it is 

 probable that the excessive amount of diarrhoea in this group of children 

 was due to bacterial changes which were not neutralized by heat or to 

 living bacteria which were not killed, yet it is only fair to consider that 

 the difference was not very great and that the infants of this group were 

 under surroundings not quite as good as those on the purer milk. 



Finally, we come in this comparison to the infants who received 

 the cheap store milk Pasteurized. This milk had frequently to be 

 returned because it curdled when boiled, arid contained, according to 

 the weather, from 4,000,000 to 200,000,000 bacteria per cubic centimetre. 

 In these infants the worst results were seen. This is shown not only 

 by the death rate, but by the amount and the severity of the diarrhoeal 

 diseases, and the general appearance of the children as noted by the phy- 

 sicians. Although the average number of bacteria in the milk received 

 by this group is higher than that received by the previous group, the 

 difference in results between this group and the previous one can hardly 

 be explained by the difference in the number of bacteria. The varieties 

 of bacteria met with in this milk were more numerous than in the better 

 milk, but we were unable to prove that they were more dangerous. 

 Probably the higher temperature at which the milk was kept in transit 

 and the longer interval between milking and its use allowed more toxic 

 bacterial products to accumulate. 



Summary. The observations here recorded were made upon the 

 groups of infants for periods of about three months only, and the con- 

 clusions 1 drawn relate especially to the more immediate effects of the 

 milk: 



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

 the infants observed in the investigation was appreciably affected by 

 the kind of milk or by the number of bacteria which it contained. The 

 different grades of milk varied much less in the amount of bacterial 

 contamination in winter than in summer, the store milk averaging 

 only about 750,000 bacteria per cubic centimetre. 



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 contami- 

 nation 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 



1 These conclusions were drawn up by the writer in association with Dr. L. E. Holt, after a joint 

 study of the results obtained in the studies above recorded. 



