Variations in Yield Mark. 55 



yield, and its weight-tension inside the udder sack; than 

 which no fact is more clear and certain; while the influ- 

 ence of weight-strain is clear and very noticeably evident, 

 in nearly all good cows. 



1 he influence of yield and its weight-strain in increasing 

 the size of the udder, and extending the hight, width, and 

 surface area of the Yield Mark, is shown in Plate III., 

 Fig. I, and its section, Fig. 2, and again in Fig. 4; five 

 successive sizes of udder, and upward extensions of udder- 

 sack being marked ; while the Breech-figure view exhibits 

 the extension of the Yield Mark, or Index of Yield, as 

 yield-weight strain extends it higher and wider, according 

 to successive increase in yield and udder growth ; and milk- 

 weight, or gravitating weight-force, and tension in the 

 udder. The reason why the hair of the Yield Mark is 

 distinctly reversed, as appears most conspicuously, when 

 this Index of yield is large, is because the force of weight- 

 strain in the bottom of the udder is greater, and longer in 

 operation there than in any other parts of milk cows. 

 And, while the weight-strain, or force of gravitation, has 

 no influence on the quality of milk, the influence of ten- 

 sion, arising from weight of yield, extends farther upward 

 and outward to the regular or irregular outlines, forming 

 the limits of the Yield Mark; reduced degrees of strain 

 extending, in many cases, beyond, as shown in the va- 

 rious directions of the hair, inthe border shading of the 

 mark; and on the variformed surfaces of the thighs, as 

 roughly illustrated in the Figs. — Plates I. and IV. So the 

 variations in the outline forms and boundaries of the 

 Yield Mark result from variations in form of breech- 

 growth, and in the muscles of the thighs, under the mark ; 

 while the influence of the strain resulting from milk-weight 

 in the udder extends as far as the skin of the thighs is loose, 

 so turning the hair from its natural direction, the reversed 

 hair, in fact, leaning back in the opposite direction to the 



