BACTERIOLOGICAL STUDIES OF MILK SUPPLIES 



157 



A graphic representation of these bacterial counts together with 

 the reactions is found in Chart I. Nine samples of the twenty-one 

 are found to exceed 150,000 germs per cubic centimeter. Twelve 

 of the twenty-one are not above 100,000 germs per cubic centimeter. 

 One is at once struck with the great difference between some of these 

 samples and others. We may ask why the Sample No. 11 should be 

 so low in bacterial count and Nos. 2, 14, 16, 17 and 19 should be so 

 high. All of these are from licensed producers and all are taken in 

 the summer. 



From our knowledge of the means of contamination of milk it is safe 

 to assume that some of these milks have not been properly handled. 

 This chart disclosed another interesting fact. If a comparison is made 

 between the height of the bacterial content column and the reaction 

 column in each sample one sees that the reaction taken in the early 

 hours after milking will seldom give any clue to the desirability of the 

 milk as a food. For instance, No. 14 shows a lower acidity than No. 

 6, and yet No. 14 shows a germ content of 2,790,000, and No. 6 only 

 447. This is due to the fact that many of these germs cause the forma- 

 tion of alkali, and especially in the early hours. Later the germs of 

 the lactic acid class predominate and finally cause acid formation and 

 curdling of the milk. We now know there are many worse things that 

 may occur to milk than souring, for many of these germs which pro- 

 duce alkalies form highly poisonous compounds. 



CHART II 



Samples of Milk Showing an Initial Count of 100,000 or Less 



Summer* 



Winter* 



Reaction 



Hours after 

 Milking 



Butter Fat: 

 Percentage 



49,086 

 35 



100,000 

 70,000 



100,330 



SI 



674 



71,080 



447 

 1,140 



17,457 

 23,828 



13 



5* 



• Bacteria per cubic centimeter. 



