1846.] On the Milk of the Cow. 139 



tissues which are then converted into casein. The cow, however, 

 must be tempted to eat much, and her pasture must be changed 

 often. This plan for the production of cheese differs from that of 

 soiling, where much butter is the object, when the cow is to be 

 kept quiet and fed on rich juicy grass in the stall. 



The author concludes his paper in suggesting the best methods 

 of preserving milk. But, in the first place, how is it that milk 

 becomes sour? The first change is by the action of oxygen on 

 the casein, which is apt to run into putrefaction, and when a 

 change begins in one element, analogous changes begin in the 

 others, which results finally in the production of vinegar. Good 

 butter cannot be made when the elements are oxidated ; and in 

 this case the casein passess into a state of putrefaction, vitiates 

 the butter, inasmuch as butter always contains some casein. 

 Sometimes so much as to possess the flavor of cheese. The prin- 

 cipal object in view in the preservation of milk, says the author, 

 and we now^ use his language, is 



To prevent the commencement of this putrefaction. One 

 method has been termed scalding the milk, and is generally used 

 in dairies. It consists in heating the milk until the oxygen of the 

 air acts upon the casein, and forms a pellicle on its surface. The 

 milk should then be left to perfect repose. The pellicle excludes 

 the air from the soluble casein. The partial oxidation by which 

 the pellicle was produced, is effected at too high a temperature to 

 enable the decay to pass into putrefaction. When this operation 

 is skilfully performed, the milk remains quite good for four or 

 five days. But there is a risk of failure in this process, and it is 

 only adapted for small dairies. 



The best method, which I have seen used in practice w^th much 

 success, seems to be to induce the acetous fermentation in the milk. 

 For this purpose, the cream or milk, being placed in a proper ves- 

 sel, should be surrounded by hot water. The heat which I find to 

 answer best is from 100° to 110°. A cloth may be thrown over 

 the whole to retain the heat, and as the water cools, it should be 

 removed and replenished with hot water of the above temperature. 

 In a few hours the cream acquires the smell and taste of vinegar. 

 The changes which I have described above ensue. In large dai- 

 ries a portion of this soured cream or milk may be added to fresh 

 cream or milk, which should be kept in a room possessing a tem- 

 perature of 60°. By adding this soured cream to the fresh milk, 

 we furnish an acid, by w^iich the sugar of milk is converted into 

 grape sugar. The curd then acts upon the grape sugar, and con- 

 verts it into alcohol. The latter by oxidation becomes acetic acid, 

 and thus the whole mass of milk is rendered sour, the casein coag- 

 ulated, and therefore protected from immediate putrefaction. The 



