Origin of Yield Mark. 47 



If three elastic sacks be suspended to receive flour or 

 grain from the carriers above— the second and third be- 

 ing severally inside the other— the flour or grain will first 

 press down on the bottom of the inner sack, or skin layer, 

 secondly, on the bottom of the middle one, and lastly on 

 the bottom of the outer sack, alias skin layer. This weight 

 pressure being chiefly on the inner sack or layer, draws 

 that layer down most and farthest; the middle layer is 

 drawn down less, while the outer sack or layer is drawn 

 down but little. 



The weight of milk and glands together, the gland 

 weight varying from one-third to half that of the milk, 

 gives a weight pressure of 12 lbs. to each quarter of a four- 

 gallon udder. Now assume the quarter, figure 5, to have 

 this 12 lb. weight of a full gland in it, and that the out- 

 side layer is correspondingly fixed, and the evident effect 

 is that the force of gravity, or the 1 2 lb. weight force in 

 the direction of the arrow, presses down on the inner sur- 

 face at the bottom of the bag, drawing down the inside 

 skin layer first and most, the middle layer being pressed 

 down secondly and less, while the outside layer (or sack,) 

 being strained but little, serves as a fulcrum or fixed point 

 in which the hair is fixed as on a pivot, and while its root 

 ends are drawn down, its outside of hair growth is in 

 this way turned upward. In this way the 12 lb. weight 

 force bearing down on the bottom in each quarter, draws 

 down the inner layer through which the hair roots extend, 

 as shown in figure 5, so drawing down the root ends of the 

 hair, and bringing the skin layers, Fig. 5, close together, as 

 shown in figure 6, at the same time turning the outside 

 growth of hair in an upward direction, as shown on the 

 back udder in the same figure. 



There would be no difference in this result whether the 

 skin be formed of three layers as in figure 5, or two, with 

 connective substance between, as in figure 7. From the 



