48 Cattle Problems. 



pressure of the milk weight in the bottom of the udder, 

 figure 7, forces the skin layeos close together, as in figures 

 6 and 8, in this way drawing down the root ends and re- 

 versing, or turning the outside hair upward as in fig- 

 ures 6 and 8, and in the whole extent of the Yield Mark 

 on the upper back udder. In this simple way the Yield 

 Mark, on milk cows is formed by pressure of the milk 

 weight itself, in the bottom of the udder, by and accord- 

 ing to the force of gravitation.* 



The size of the Yield Mark so formed, is larger or 

 smaller according to the weight of the glands and yield 

 together, as the quantity, weight, and weight tension of 

 yield, the size of udder, of course, corresponding to the 

 measure of its )'ield, and the size of the "Yield Mark;" 

 the necessary consequence of pressure or weight strain, 

 corresponds to the extent of milk-weight, by and accord- 

 ing to which this natural mark or Index of yield is 

 formed. 



In the manner described, 'Ca& force of gravitation, or milk 

 and gland weight, are combined, in drawing down the hair 

 roots that extend through the inner skin layer, so reversing 

 the natural direction of tlie hair on the loose skin of the 

 twist, or iiffcr part of the back udder, which indicates that 

 the tension of the milk weight extends upward on the 

 twist, and higher and wider on th« thighs, according to 

 the quantity of yield, and its weight strain. 



*ln common window-blinds, the outer edffes ni-e turned up precisely to the 

 Slime extent that the inner ed,i;es are turned downwaril. whicll illustrates the 

 turning of the hair of the Yielu Mauk u])ward by llu- drawing of the root 

 ends downward. A very simple andelfecti>e illustration uf the manner in which 

 Ihe Yield MARii is fornu'd can be made with six or nine narrow strips of 

 l)asteboard. Two ur Ihrce of the shorter strips lieins fustoued together with 

 common hair pins, an iueh apart, across the longer strips. The longer strips 

 are half an incli apart, and nuiy represent two en- three skin biyers, the shorter 

 strips representing hairs. Now hold the rough model up ^■ertieally. or put it 

 on the table, keeping one outside strip Jlxed^ drawing the other outside strifis 

 down. This movement will bring down the inner ends of the crt>ss strips, 

 rein-eseuting the root ends of tlie hair, as the long strips — skin layers 

 are brought near or close togi'tlier ; the s;iuu' movement turning up the out- 

 .side ends of the strijis, representing- the luur ; aiul sirowing the manner 

 in which the hair is griidiially reversed in fcu-iuiug llu- Yikld ^Iariv on the 

 upper back ndder or twist of milk cows, in size aeeortling to their yield. 



