690 BACTERIOLOGY OF MILK 
Statistics of 317 epidemics of typhoid fever, 125 epidemics of scarlet 
fever, 51 epidemics of diphtheria and 7 of septic sore throat are set 
forth therem. This hst is by no means regarded as complete; it 
includes only those epidemics in which satisfactory evidence of the 
origin and spread of disease is available. 
Milk that is free from frankly pathogenic microorganisms is not 
necessarily a suitable food for man ; it may be deadly for young children 
and infants. In the past little was definitely known of the relation of 
market milk to the high death-rate among children, although a very 
direct connection was suspected. Park and Holt, however, made an 
extensive study of this very important question and their results are 
illuminating. Their plan was to feed ten groups of children with milk 
of known origin; this milk was mixed to secure uniformity and divided 
into ten portions. One-half, containing about 1,200,000 bacteria per 
cubic centimeter at the time of feeding, was distributed to one group 
the other half was pasteurized before delivery. It contained, on the 
average, about 50,000 viable bacteria per cubic centimeter. The 
observations were carried on during the three warmest months of the 
year. Within a week nearly two-thirds of the infants fed with raw 
milk developed mild or severe diarrhea; about 25 per cent remained 
well. Of those receiving pasteurized milk about 25 per cent developed 
diarrhea and 75 per cent remained well. A similar experiment was 
made the following summer. Their conclusions were:^ 
"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 market 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 centimeter. 
"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 
temperature at which it has been kept. When the 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 centimeter are cer- 
tainly deleterious to the average infant. However, many infants 
take such milk without apparently harmful results. Heat above 170° 
1 Park and Holt; Arch. Pediat., December, 1903, p. S81. 
