166 SCIENCE AND PRACTICE OF CHEESE-MAKING 



It is seen that the different breeds represented 

 separate into two general groups in relation to the 

 ratio of fat to casein. In the case of the first five 

 breeds in the list, this ratio does not vary widely. 

 The milk containing least fat contains the largest 

 amount of casein in relation to fat; but, even though 

 the percentage of fat in the case of this group in- 

 creases to 4.89, as in the case of the Devon breed, 

 the ratio of casein does not diminish greatly. The 

 Guernsey and Jersey breeds constitute the second 

 group, the fat being high in amount but the casein 

 relatively low. 



Influence of stage of lactation upon the relation 

 of fat and casein. We have already noticed that 

 the percentage of fat and of casein increases grad- 

 ually and quite regularly during the period of lacta- 

 tion. We will now consider the question as to 

 whether these constituents increase in the same 

 ratio. 



RELATION OF FAT AND CASEIN DURING LACTATION 

 PERIOD 



