BACTERIOLOGY OF MILK IN ITS RELATION TO DISEASE 461 



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 centimetre are certainly dele- 

 terious to the average infant. However, many infants take such milk 

 without apparently harmful results. Heat above 170 F. (77 C.) not 

 only destroys most of the bacteria present, but, apparently, some of their 

 poisonous products. No harm from the bacteria previously existing 

 in recently heated milk was noticed in these observations unless they 

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

 edly deleterious. 



4. AYhen milk of average quality was fed sterilized and raw, those 

 infants who received milk previously heated did, on the average, much 

 better in warm weather than those who received it raw. The differ- 

 ence was so quickly manifest and so marked that there could be no 

 mistaking the meaning of the results. The bacterial content of the 

 milk used in the test was somewhat less than in the average milk of 

 the city. 



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

 seemed to have any special importance in relation to the summer diar- 

 rhoeas of children. The number of varieties was very great, and the kinds 

 of bacteria differed according to the locality from which the milk came. 

 None of the 139 varieties selected as most distinct among those obtained 

 injured very young kittens when fed in pure cultures. A few cases of 

 acute indigestion were seen immediately following the use of Pasteur- 

 ized milk more than thirty-six hours old. Samples of such milk were 

 found to contain more than 100,000,000 bacteria per cubic centimetre, 

 mostly spore-bearing varieties. The deleterious effects, though striking, 

 were neither serious nor lasting. 



At the present time there is in New York City no general sale from 

 stores of " Pasteurized" or "sterilized" milk; so that here it is very 

 rare for such milk to be used thirty-six hours after heating. 



6. After the first twelve months of life, infants are less and less affected 

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

 observations, when the milk had been kept cool the bacteria did not 

 appear to injure the children over three years of age, at any season of 

 the year, unless in very great excess. 



7. Since a large part of the tenement population must purchase its 

 milk from small dealers, at a low price, everything possible should be 

 done by health boards to improve the character of the general milk 

 supply of cities by enforcing proper legal restrictions regarding its 

 transportation, delivery, and sale. Sufficient improvements in this 

 respect are entirely feasible in every large city to secure to all a milk 

 which will be wholesome after heating. The general practice of heat- 

 ing milk, which has now become a custom among the tenement popula- 

 tion of New York, is undoubtedly a large factor in the lessened infant 

 mortality during the hot months. 



8. Of the methods of feeding now in vogue that by milk from central 

 distributing stations unquestionably possesses the most advantages, 



