THH DAIRY HERD 65 



resentative sample even when the milk has stood undis- 

 turbed a few minutes. This method of sampling should 

 be employed, therefore, where there is much variation in 

 the quantity of night's and morning's milk, or where 

 the milk is not apt to be thoroughly mixed before samp- 

 ling. 



Preservatives. Milk can not be satisfactorily tested 

 after it has soured, owing to the difficulty of securing 

 an accurate sample. This makes it necessary to place a 

 small amount of preservative in the composite sample 

 jar before the sampling is begun. 



The best preservatives for this purpose are corrosive 

 sublimate, formalin and bichromate of potash. All of 

 these are poisons and care must be taken to place them 

 where children and others unfamiliar with their poisonous 

 properties, can not have access to them. For conve- 

 nience, the bichromate of potash and corrosive sublimate 

 have been put up in tablet form, each tablet containing 

 enough preservative to keep a pint of milk sweet from 

 one to two weeks. The bichromate of potash can be 

 procured from all druggists, and a quantity not to exceed 

 the size of a, pea should be added to each pint composite 

 jar. A larger quantity is liable to interfere with the 

 testing. 



Testing With the Babcock Test. The method of 

 operating the Babcock test is explained in detail in chap- 

 ter XVIII. 



Calculating Butterfat and Butter Yield. The 

 monthly butterfat yield of each cow is determined by 

 multiplying the total pounds of milk for the month by 

 the per cent of butterfat it contains. For example, if 

 cow No. i produced 850 Ibs. of milk testing 4.2% fat, the 



