36 THE STORY OF MILK 



bovine tuberculosis is hardly ever transmitted to grown 

 persons and seldom to children. Neither is it hered- 

 itary. Nevertheless, wherever it is possible to have 

 the herd tested with tuberculin, segregating, if not 

 killing, the animals which show by reaction that they 

 are somewhat tuberculous, it should be done. Milk 

 from such cows should always be pasteurized. 



Milk as a Disease Carrier. — A greater danger lies 

 in the fact that, warm as it comes from the cow, milk 

 is an ideal medium for human disease germs to grow 

 in, and may thus become a great conveyor of such 

 germs. For this reason it is of the greatest importance 

 that the milkers are healthy and clean, that the udders 

 and teats be free from dirt, and the milk pail covered 

 as far as possible; the barn must be clean, and every 

 source of infection excluded. This fact also points to 

 the advisability of pasteurization. On page 23 a chart 

 is shown, published by the Toronto Board of Health 

 and indicating the temperatures at which various germs 

 of disease are made harmless. 



Bacterial Count. — The test for clean milk now mostly 

 used is the ''Bacterial Count,'' the number of bac- 

 teria — or rather colonies of bacteria — found in a cubic 

 centimeter of the milk. It would be better if the nature 

 or quality of the bacteria could be taken into consid- 

 eration as well as the quantity, but that being as yet 

 impracticable, the next best thing is to depend upon 

 the number. Ordinary good milk often contains hun- 

 dreds of thousands of bacteria in a cubic centimeter, 

 but where the greatest cleanliness is observed the 

 number may be less than 1 ,000. 



Certified Milk is now sold in many cities which, ac- 

 cording to varying city ordinances, is guaranteed to 



