CIRCULATION. 67 



CIRCULATION. It is not necessary to our purpose to go 

 into any extended explanation of this important animal 

 function, but it will be sufficient to mention that this con- 

 sists in the incessant motion of the blood, propelled by the 

 heart through the arteries to all the inner and outer sur- 

 faces of the body, permeating every tissue; from thence 

 returning by the veins to the heart, and thence to the lungs, 

 where by contact with the oxygen of the air, it is purified 

 and rendered fit to nourish the tissues, and returning. from 

 the lungs to the heart, it is sent again on its rounds to every 

 part of the body. We explained in a previous chapter the 

 appearance and chemical composition of the blood. We 

 have pointed out how the blood is elaborated from the 

 food in process of digestion, and then absorbed into the 

 circulation. 



The heart is composed of strong muscular fibre, and di- 

 vided into four cavities, having valves which regulate the 

 flow of blood. These muscles expand and contract with 

 regularity, producing what we call "heart-beats." There 

 are something like four of these " beats " to one inspira- 

 tion of the lungs. 



THE PULSE. As nature is regular, these beats or the 

 pulse becomes an indication of health or an abnormal 

 state of the system, and it is therefore an accomplishment 

 in a cattle-feeder to understand the pulse of different ani- 

 mals. This will give him a better knowledge of the real 

 condition of the system than any outward appearance. 



Dr. James Law (in his Veterinary Adviser) says: The 

 pulse in full-grown animals at rest may be set down per 

 minute as : Horse 36 to 46 ; ox 38 to 42, or in a hot 

 building, with full paunch, 70 ; sheep, goat, and pig, 70 to 

 80. In old age it may be 5 less in large quadrupeds, and 

 20 to 30 in small ones. Youth and small siie imply a 

 greater rapidity. The new-born foal has a pulse three 

 times as frequent as the horse, the six-months colt double, 



