Duration of Yield. 67 



Mark is the result of maximum yield, by cows that are so 

 Indexed. And, if the yield has shrunk, it can be restored 

 to its previous maximum quantity, m healthy cows, by suit- 

 able feeding. The smaller the yield, the earlier embryo 

 growth will dry up the cow ; the larger the yield, the later 

 it will hold out. Thus while reduction of yield represents 

 increase of embryo growth, the quantity of yield and its 

 duration are represented in the size of the Yield Mark, in 

 a large majority of cows. 



