ii2 MILK [vi 



While the application of heat is the most favour- 

 able method of effecting sterilisation, the preservation 

 of milk may also be effected by the application of 

 cold. Cold, however, while it may retard the de- 

 velopment of bacteria, does not, unfortunately, entirely 

 destroy them. Certain pathogenic germs have been 

 found capable of resisting the lowest attainable 

 temperatures. If kept in refrigerators, rnilk remains 

 sweet for a long time. Unfortunately, a serious 

 objection to such treatment of milk is the separation 

 of the cream from the skim milk. A change in the 

 physical condition of the milk seems to be effected, 

 with the result that milk which has been frozen is 

 very different from ordinary milk. It is for this 

 reason that the attempts which have been made, on 

 a large scale, more especially in Paris, have resulted 

 in failure. We may add that cooling milk to a 

 temperature of 10 C. (50 Fahr.), while it does not 

 affect the physical condition of the milk, exercises an 

 important preservative influence. 



Chemical Agents. Various chemical agents 

 have again and again been used as preservatives. 

 Obviously the most effective disinfectants, such as 

 corrosive sublimate, carbolic acid, etc., cannot be used 

 on account of their poisonous nature ; whereas such 

 substances as salicylic and boracic acids, carbonate 

 of soda, quicklime, and hydrogen peroxide have to 

 be used in such quantities, if they are to be at all 



