54 THE HISTORY OF ANIMALS [fl III 



through the heart. But the aorta passes from the heart, and 

 the great vein is membranous and like skin, but the aorta is 

 narrow and very sinewy, and as it is continued towards the 

 head and the lower parts of the body, it becomes narrow and 

 quite sinewy. 



4. A portion of the great vein is first of all extended up 

 wards from the heart to the lung, and to the junction of 

 the aorta, this vein being undivided and large ; from this 

 place it divides into two branches, the one towards the lung, 

 and the other to the spine and the lowest vertebra of the 

 neck. The branch which goes to the lungs is first divided 

 into two branches, and afterwards it is continued upon every 

 tube and passage of the lungs, greater to the greater, and 

 less to the less, so as to leave no part in which there is not 

 a passage and a small vein. These last are invisible from their 

 minute size, so that the whole lung seems to be full of blood. 



5. And the passages from the vein are above the tubeswhich 

 extend from the trachea. And the vein which is continued 

 upon the vertebra of the neck, and upon the spinal column, 

 returns again to the spine, asHomer writes in his poems : &quot;He 

 cut off the whole vein which passes up the back and returns 

 again to the neck;&quot; 1 and from thisvein brandies extend to each 

 rib and to each vertebra ; but that which is upon the vertebra 

 near the kidneys branches in two directions. These branches, 

 then, of the great vein are subdivided in this manner. 



6. And above these, from that part which is continued from 

 the heart, the whole is again divided into two directions, for 

 some reach to the sides and the clavicles, and afterwards 

 through the armpits to the arms, in the human subject, but 

 in quadrupeds to the fore-legs, to the wings in birds, and to 

 the pectoral fins in fishes. The commencements of these veins, 

 when they are first of all divided, are called jugular veins ; 

 and having branched off in the neck from the great vein, they 

 are continued to the trachea of the lungs. And if these 

 veins are held on the outside, men fall down dead with in 

 sensibility, with closed eyes, but without choking. 



7. Extending in this manner, and receiving the trachea 

 between them, they reach the place where the jaws unite 

 with the head ; and again from this point they are divided 

 into four veins, one of which bends backwards and descends 



1 IliacL xiii, 546. 



