BACTERIA IN THE INDUSTRIES. 105 



so that the bacterial development is afterward even more active than before. 

 Sterilizing at lower temperature (50 to 80 C.), known as pasteurizing, does 

 not interfere with the nutritive qualities of the milk, but destroys_ihe_bacteri- 

 cidal properties, as already mentioned. The process is, however, generally 

 recommended by physicians. A simple home method may be carried out as 

 follows (Roger): 



Milk is most conveniently pasteurized in the bottles in which it is deliv- 

 ered. To do this use a small pail with a perforated false bottom. An 

 inverted pie tin with a few holes punched in it will answer this purpose 

 Punch a hole through the cap of one of the bottles and insert a thermometer. 

 Set the bottles of milk on the pie tin in the pail and fill the pail with water 

 nearly to the level of the milk. Put the pail on the stove or over a gas flame 

 and heat it until the thermometer in the milk shows not less than 65 C. nor 

 more than 70 C. The bottles should then be removed from the water and 

 allowed to stand from twenty to thirty minutes. The temperature will 

 fall slowly, but may be held more uniformly by covering the bottles with a 

 towel. The punctured cap should be replaced with a new one, or the 

 opening sealed with wax or paraffin, or the bottle may be covered with an 

 inverted cup. 



After the milk has been held as directed it should be cooled as quickly 

 and as much as possible by setting in water. To avoid danger of breaking 

 the bottle by a too sudden change of temperature, this water should be warm 

 at first. Replace the warm water slowly with cold water. After cooling, 

 milk should in all cases be kept at the lowest available temperature. 



It should be remembered that pasteurization does not destroy all bacteria 

 in milk, and after pasteurization it should be kept cold and used as soon as 

 possible. 



Rosenau sums up the pros and cons of milk pasteurization as follows: 



Advantages. The advantage of pasteurization is that it is a cheap and 

 effective means of preventing the transmission of infectious diseases such as 

 tuberculosis, typhoid fever, diphtheria, scarlet fever, etc., commonly spread 

 by milk. 



Disadvantages. a. Pasteurization promotes carelessness on the farm 

 and dairy, etc. (This may be controlled by proper regulations, inspections 

 and laboratory examinations.) 



b. Pasteurization renders milk less digestible. (While it is generally 

 conceded that boiled milk commonly induces constipation, the majority of 

 the evidence plainly indicates that pasteurization has little, if any, effect on 

 the digestibility of the milk.) 



c. Pasteurized milk favors the production of rickets and scurvy. (There 

 is no proof to this effect and authorities agree that the danger is slight; and, 

 further, that it may readily be obviated.) 



