Part II.] PASTEURIZATION OF MARKET MILK. 101 



dairies, the examination of milk in the city laboratories, — all 

 these activities are helping to reduce the danger of infected 

 milk and to minimize the occurrence of epidemics of milk-borne 

 diseases. But their service, after all, is not general, it is limited; 

 the task is too immense, the expense involved too great, and 

 the results too uncertain for the adequate protection of the 

 public. The milk furnished to any one of our larger cities 

 comes from thousands of farms; it is produced by tens of 

 thousands of cows and handled by tens of thousands of persons. 



The difficulty of complete supervision and protection is fur- 

 ther augmented by the frequent change of cows and personnel 

 on the farms. New cows enter the herds, new employees take 

 the place of old ones, all of which may happen between periods 

 of inspection. The virulence of some of the disease germs is 

 such that infection occurring to-day may spread disease to- 

 morrow. Perfectly healthy employees may serve as carriers of the 

 germs of disease, so that protection is beyond the power of the 

 inspector. 



The hope that certified milk, which is milk produced under 

 the supervision of a medical commission, and which, from the 

 sanitary standpoint, is regarded as the most ideal milk, may 

 ultimately solve the problem of a sanitary milk supply is no 

 longer cherished. Even certified milk is not an absolute safe- 

 guard against infected milk. But assuming that it were, its high 

 cost of production limits its output, and its high price to the 

 consumer confines its availability to the wealthy classes only. 

 The great army of milk consumers, therefore, must look else- 

 where for a safe milk supply, and right here is where pasteuriza- 

 tion comes to the rescue. 



By pasteurization of milk is now understood the exposure of 

 milk to temperatures high enough and for a sufficient length of 

 time to destroy the great majority of the living germs it may 

 contain without impairing its digestibility and marketable prop- 

 erties. Bacteriological analysis of milk and cream show con- 

 clusively that pasteurization, properly executed, is very efficient; 

 it is capable of destroying on an average 99.9 per cent of the 

 bacteria present, and it eliminates from the milk entirely the 

 germs of such milk-borne diseases as tuberculosis, typhoid fever 

 and diphtheria, etc. 



