756 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



weight and the transference of the velocity of the animal to the moving 

 mass. All the arrangements of the hind extremities are especial!}' favor- 

 able for the production of power; thus, reduction of the anterior pelvic 

 angle, accompanied by powerful development of the hips and lumbar 

 muscles. In animals, therefore, with short bones, slight angularity, and 

 short muscles the conditions are most favorable for drawing heavy 

 weights, while animals with long bones, long muscles, and highly 

 angular joints are especially adapted for speed. The position of the 

 centre of gravit}* in the animal body is especially of influence in the 

 developing power. Since the body weight is the moving force its 



FIG. 312. HAULING FROM A COLLAR. (Colin.) 



The line, A B, indicates the direction of the resultant of the propelling forces through the lines, A D 



and B C. 



action will be the more developed the farther forward the centre of 

 gravity, since in this way the power-arm of the lever will be increased. 

 Consequently, draught animals sink the head and neck. The power 

 developed by horses has been estimated by raising a certain weight 

 to a certain height by a rope passing over a pulley. Experiments so 

 made have shown that a moderately strong horse may raise a weight 

 of ninety-five kilos in one second to 0.8 meter high, from whence horse- 

 power of seventy-six kilogram meters has been deduced. In the same 

 way the power 'of an ox has been found to be forty-seven and an ass 

 twenty-nine kilogram meters. In drawing a weight, the full power of an 



