142 ARISTOTLE'S ANHOMCEOMERIA 



Aristotle proceeds to describe the various blood-vessels 

 which pass from the parts of the great blood-vessel above 

 the heart. He says that a part of the great blood-vessel 

 passes upwards as an undivided blood-vessel of large size, 

 and that two vessels extend from it. One of these goes 

 towards the lungs and divides into two vessels, one for each 

 tracheal tube ; these two vessels break up into smaller and 

 smaller vessels which ramify through the substance of the 

 lungs, so that the whole of these seems to be full of blood. 

 The other vessel, which extends from the upper part of the 

 great blood-vessel, passes to the spinal column and the last 

 cervical vertebra. 



The great blood-vessel, referred to in the above state- 

 ments, is clearly the pulmonary artery, and Aristotle's 

 description of the arrangement of the blood-vessels passing 

 from it to the lungs will be more conveniently discussed in 

 Chapter xi. His assertion that a blood-vessel extends from 

 the great blood-vessel to the spinal column and the last 

 cervical vertebra is by no means easy to understand. The 

 pulmonary artery has no branch of this kind. His further 

 description of the great blood-vessel and its branches almost 

 suggests that he was referring to the large azygos vein, but 

 it does not seem to be possible to identify the blood-vessel 

 which he so strangely connects with the pulmonary artery. 

 His description of the two blood-vessels passing from the 

 upper part of the great blood-vessel is an example of 

 passages in which a fairly good description is followed by 

 an apparently inexplicable statement. Such passages often 

 occur in his description of the arrangement of the blood- 

 vessels, and, in some cases, it is almost futile to attempt to 

 do more than refer to them. 



Aristotle proceeds to say that, from the " whole " (which 

 should be the vena cava superior), blood-vessels pass to the 

 sides and collar bones and thence to the arms in men, to the 

 forelegs in quadrupeds, to the wings in birds, and to the 

 pectoral fins in fishes. The parts of these blood-vessels near 

 where the branching takes place he calls the jugulars. He 

 also says that blood-vessels pass from the great blood-vessel 

 to the neck and along the trachea, and that, when these 

 blood-vessels are held on the outside, men sometimes fall 

 down insensible, with eyes closed, but without being choked. 

 These blood-vessels, he says, extend as far as the ears, 

 where they branch off into four vessels, one of which turns 

 back and passes through the neck and shoulder on its way 



