THE BLOOD-VESSELS. 393 



and other parts in the head; the external, hj its numerous 

 branches, is distributed to the various parts of the head, face, 

 and parts within the mouth. Of its branches, the largest is 

 called the suhmaxillarij, which passes forward under the angle 

 of the lower jaw, and at about one-third of the way forward 

 curves across the bone to the- outside of it, to go to the face 

 and nose. It is just where this artery crosses the jaw that 

 the pulse of the horse may be most conveniently felt, by grasp- 

 ing the jaw with the hand, and with the points of the fingers 

 under it resting on the artery. 



The Jilnder, or j^osterior, aorta starts from even with the 

 dorsal vertebrae, passes upward and backward to the under 

 side of the spine, with which it lies in contact, as far back as 

 the lumbar vertebrae, where it divides into four large branches. 

 In its course, however, it gives off several branches and pairs 

 of branches. The first two, called hroncMal a7'teries, pass into 

 the lungs along with the bronchial tubes, to supply the lungs 

 with blood. The next branch goes to the gullet, sending twigs 

 to parts in its neighborhood. The next are several pairs, 

 which go to the spaces between the ribs. As it passes from 

 the chest into the abdomen, the aorta gives off the large branch 

 which supplies the diaphragm. Further back it gives off one 

 large, short branch, called the coeliac artery, which divides into 

 three branches, one going to the spleen, another to the stom-^ 

 ach, and the other to the liver. 



The next branch starts from the under side of the aorta, 

 passes downward, and divides into from eight to twelve 

 branches, which supply the intestines, and the great folded 

 membrane, called the mesentery, which enfolds them. These 

 are called the mesenteric arteries. 



The renal arteries are the next pair. One goes to each kid- 

 ney. The next are the sjyermatic arteries, which, in the male, 

 go to the testicles; in the female, to those bodies called the 

 ovaries, and the tubes which connect them to the uterus, or 

 womb. 



