Hand-milking and Udder-growth. 21 



from tlie pressure of the milk. So the udder increases in 

 size with the gradual or rapid increase of milk-yield, and 

 its corresponding increase of expansive force, from, and as 

 the direct consecjuence of, accumulating the semi-daily 

 milk yield in the bag. This is so obvious that it would 

 not have required remark, except to obviate misapprehen- 

 sion of the facts, which has been found more frequent than 

 seemed probable. 



But there is another force — a force that pervades the 

 entire solar system — which of course includes both tlie cow 

 and her udder, which has great influence in the enlarge- 

 ment of this milk reservoir; namely: — 



The force of Gravitation or the 70i'ight oi the mift. The 

 milk weight increases, of course, correspondingly with its 

 bulk, or measure, and the pressure or strain of this weight 

 on the bottom of the inner surface of the bag is increased 

 directly in the proportion that yield of milk increases; and 

 this weight force continues as long, and in the same pro- 

 portion, as yield and its pressure are continued in the 

 udder. The downward pressure and tension due to the 

 presence of milk in the udder, and the influence of this 

 tension and pressure by its weight are as constant, and evi- 

 dent, and certain as the presence of the milk itself, after it 

 has been formed in the glands. 



The regularly repeated downward tension on the bottom 

 of the udder sack, is constantly tending to deepen the bag 

 according to the amount and weight of milk; the down- 

 ward pressure and its resulting tension on the skin that 

 forms the bag, being increased correspondingly with the 

 increase of yield. To the weight of milk, primarily, must be 

 added the weight of the glands in which the milk is formed. 

 The glands, with the lobes or quarters which inclose them, 

 may weigh from a third to half as much as the weight of 

 the milk itself. The gland weight is variable, but is in- 

 cluded in, and makes up a large percentage of the down- 



