Variations in Yield Blark. 57 



IS farthest from the milk-man,* which is the left side, as 

 looked at from behind ; and so the left side of the bag is 

 stretched and deepened, and the left side of the Yield 

 Mark extended outward and upward, by the semi-daily 

 repetition of this extra strain, that is inseparable from the 

 hand-milking process. And so, too, the form and propor- 

 tion of the Yield Mark and udder are each changed to 

 some extent, and the size of the left side is increased, as the 

 mseparable effect of semi-daily tension on that side of the 

 udder in stretching and drawing it over — see Fig. 12, Plate 

 V. — to secure its contents in the pail ; and this seems to be 

 sufficiently conclusive, as to the influence of tension on the 

 Jorm of the udder, and the Yield Mark. Hence it is un- 

 necessary to add further proof, or suggest other instances 

 of analogy on the influence of tension. 



If the form of cows was generally uniform, the form of 

 their breech figures would be equally so. But there are no 

 two cows alike in the form, or in the expression of their 

 faces, or in their general growth, which includes that of 

 the breech parts. Accordingly, and consistently, there is 

 as much variation in the hight, width, and details in form 

 in the breech figures, as in the faces or other parts of cows. 

 In fact the variations in form are as numerous as the cows 

 in which they are found. And, while total s2r:e in the 

 Yield Mark increases with, and from, the increased weight 

 of augmented yield, the outline forms and margins vary 

 with the degrees of undulation, caused by variation in full- 

 ness and direction, etc. , of the flesh or thigh-muscles under 

 the skin. In some cases, fullness of muscles and extent of 

 depressions, or lower parts of the flesh surface, is greater 

 than in others; which is well shown by difference in the 

 muscles of human arms. The differences in flesh surfaces 

 as to elevated and lower parts, is similar in the breech 



*" Milk-maid," German; "milk-man," American. 

 5 



