AND THEIR FUNCTIONS. 141 



same way as the great blood-vessel, for it communicates 

 with the heart by a much narrower passage, and merely 

 extends from it, whereas the great blood-vessel passes 

 through the heart. 



Aristotle's description of the relative positions of the 

 great blood-vessel and the aorta, or rather the parts of these 

 which pass downwards along the spinal column, is not quite 

 correct, for, although most of the great blood-vessel is 

 nearer the ventral wall than the aorta, its lower part is not. 

 Again, in its downward course the aorta tends to the right, 

 so that its lower part may be more correctly said to lie in 

 front of the spinal column. It is evident, from his own 

 statement, that Aristotle was not the first to give the name 

 aorta to the blood-vessel which, since his time, has been 

 almost always called the aorta. In one of the Hippocratic 

 treatises,* not written by Hippocrates but probably by a 

 contemporary, the name aortcd is given to the bronchial 

 tubes. Aristotle does not always use the phrase " great 

 blood-vessel " in the same sense ; usually it refers to some 

 part or parts of the venae cavae and pulmonary artery, but, 

 in any particular passage, its meaning must be ascertained 

 from the context. 



The largest chamber, on the right side, to which Aristotle 

 says that the great blood-vessel is connected, is the right 

 ventricle, together with the right auricle, as explained 

 already, and the middle chamber, from which the aorta is 

 said to arise, is the left ventricle. Aristotle's statement 

 about the relative sizes of the roots of the aorta and the 

 great blood-vessel, whether this be taken to be one of the 

 venae cavas or the pulmonary artery, is incorrect. He pro- 

 bably never saw these vessels in Man, in whom there is but 

 a small difference in size between the root of the aorta and 

 the root of the pulmonary artery. Again, to take an animal 

 the heart of which he probably dissected, the root of the 

 aorta of a three-year-old ox was a little larger than the root 

 of the pulmonary artery and much larger than the root of 

 either vena cava. 



Aristotle describes the largest chamber as if it were a 

 reservoir-like part of the great blood-vessel, and it is clear 

 that he considered this chamber, or at least that part of it 

 now called the right auricle, to be a dilatation of the great 

 blood-vessel. 



* On Places in Man, c. 14. 



