DISTRIBUTION OF THE ARTERIES. 



gress to the various parts of the body, as it is carried 

 along by the arteries. What a multitude of these ves- 

 sels there must be ; it would be impossible to remember 

 all their names. 



D Tt #. And we can see but a small portion of that 

 system of vessels which transmit their contents to the mi- 

 nutest point in the body, insomuch that not the slightest 

 scratch, nor prick of the finest needle can be made, 

 without wounding them, and producing an effusion of 

 blood. The aorta, constituting the great trunk of the 

 arterial system, rising up from the arterial ventricle, 

 and suddenly bending over, passes straight down the 

 trunk of the body and lies near the spine. From its 

 arch, it gives off several large vessels which go to the 

 arms, neck and head, viz. one to each arm, called the 

 subdaman arteries, and four to the neck, face, and head, 

 the two carotids, and two vertebrals. The branches sent 

 off by these vessels supply all these parts. In its pas- 

 sage down the trunk, it sends branches to the stomach, 

 liver and spleen, and the other internal organs. In the 

 lower part of the abdomen, it divides into two, called the 

 iliac arteries, which supply the neighboring organs, 

 and the inferior extremities. The arterial branches 

 are generally given off at acute angles ; sometimes 

 however at right, and in a few instances at obtuse angles. 

 The branches are smaller than the vessels from which 

 they are given off, and thus the vessels go on decreasing 

 in size, even to their minutest ramifications. 



Emily. But as the branches taken together have ob- 

 viously a greater diameter than the trunk itself, the mo- 

 tion of the blood must be continually grower slowing, ac- 

 cording to a well known law of the distribution of forces. 

 The zig zag direction of some of the vessels, and the 

 great size of the angles at which they are given off must 

 also have a tendency to retard its motion. But I have 

 observed, in a plate of the arteries, two bending to- 

 wards each other and at last forming but one vessel ; 

 others are connected by a branch running between them. 



