SANGUIFEROUS SYSTEM. 507 



carotid commonly gives off, a superior thyroid to the thyroid 

 gland and larynx, a lingual branch to the tongue, a. facial or 

 external maxillary extensively ramified on the external and 

 internal parts of the face, an inferior thyroid which, how- 

 ever, in the short neck of man, is derived from the subcla- 

 vian, a small ascending pharyngeal to the pharynx and ad- 

 joining parts, an occipital to the posterior parts of the head 

 and neck, a posterior auricular chiefly to the external and 

 internal parts of the ear, a large temporal to the exterior 

 lateral parts of the head, and a larger internal maxillary 

 artery extensively distributed on the deep-seated parts of the 

 face, the teeth of the upper and lower jaws, and the lining 

 membrane of cranium. In the long necks of ruminating 

 quadrupeds the inferior thyroid artery is restricted to the 

 thyroid gland, and the superior thyroid to the larynx, and 

 in the myrmecophaga tridactyla both right and left superior 

 thyroid and the left inferior thyroid, have their place sup- 

 plied by a single branch from the trunk of the right brachio- 

 cephalic artery, which is ramified on the thyroid gland and 

 the larynx. 



The internal carotid artery passes in a tortuous manner to 

 the foramen caroticum, by which it enters the cranium to be 

 distributed chiefly on the anterior and middle parts of the 

 brain, the posterior parts being supplied by the vertebral 

 artery, and the membranes by the meningeal branches from 

 the external carotid ; so that the internal carotid varies much 

 in its relative size according to that of the anterior parts of 

 the brain, being a small branch in the inferior mammalia, as 

 in the lower classes of vertebrata, and a large division of the 

 common carotid in the higher carnivora, quadrumana, and 

 man. The internal carotids of the ruminantia, on arriving 

 at the sides of the sella turcica, subdivide into innumerable 

 minute anastomosing twigs, forming a rete mirabile, and these 

 twigs again unite to recompose the arterial trunks, before 

 they are distributed on the pia mater to penetrate the deli- 

 cate texture of the brain. This structure resembles that of 

 the plexuses of the brachial and femoral arteries in tardigrade 

 quadrupeds, and serves the same function in retarding the 

 impetus of the blood in the long pendent neck of these 

 animals, before entering the brain. The same structure is 

 found also in some of the more powerful carnivora, and in a 



