Breeding Power and Sterility. 119 



breed, whether large or small, but chiefly in Short-horns, 

 results from some leading influence, which does not affect 

 active cattle like most of those just named, and the lead- 

 ing difference at once appears in the wide contrast between 

 the degree of exercise taken by inactive or indolent cat- 

 tle, and that taken by the active, muscular breeds. Inac- 

 tivity leads to reduction of muscle, and to a correspond- 

 ing increase in the quantity and proportion of solid fatty 

 accumulations. But muscles rapidly or gradually die and 

 waste from disease or inaction, because their supply of 

 oxygen in the red blood ceases, and then the dead sub- 

 stance of the fibres is decomposed, and added to accumu- 

 lated fat. This results gradually when exercise is gradu- 

 ally reduced, and rapidly under abrupt and close confine- 

 ment. 



Life and large size may, it is true, be maintained in cat- 

 tle with a small amount of exercise, and a small propor- 

 tion of muscular growth and little vitality ; but without 

 abundant food, fat, and the fat-forming tendency are in- 

 creased in proportion as muscularity is reduced by inac- 

 tivity. The muscular parts comprise about half the natu- 

 ral proportion and substance of active cattle, and, includ- 

 ing the vital organs, blood-vessels, and skin, which are all 

 muscular, nearly the whole of the red blood, or nutritive 

 circulation, is contained in the muscles and muscular parts 

 or organs. 



Another important fact is, that the size of the vital or- 

 gans generally, as well as that of the muscles proper, is pro- 

 portioned to their use or activity, within normal limits, 

 the limits being determined by the extent of regular use, 

 this being conspicuously true of the lungs and digestive 

 organs, compared with the general size of animals. 



The extent of the red-blood circulation is reduced as 

 regular exercise is reduced, because the demand for nu- 

 tritive blood for the renewal of active parts, as well as 



