THE COMMON CAEOTID ARTERIES. 



595 



animals. The vessels in the arm of the sloth are so disposed that the animal can remain 

 suspended by it for long periods, and a similar arrangement is noted in the legs of birds, 

 such as the swan, goose, &c., which stand for a long time. Around the Horse's foot the 

 arteries break up into numerous divisions, and we know that this animal can remain 

 in a standing attitude for months, and even years. The rete ophthalmicum of birds is 

 arranged like the rete mirabile. The same object is sometimes attained by great tor- 

 tuosity, as we have already seen in the description of several of the arteries. Perhaps 

 the most marked example, however, is to be found in the carotid artery of the Seal, 

 which is nearly forty times longer than the space it has to traverse.) 



COMPARISON OF THE CAROTID ARTERIES OF MAN WITH THOSE OF ANIMALS. 



The common carotids of Man have a separate origin, the right arising from the 

 arteria innominata, the left from the arch of the aorta. At the interior border of the 

 thyroid cartilage, they terminate by only two branches : the external and internal 

 carotids ; the occipital artery is but a division of the former. 



Fig. 289. 



ARTERIES OF THE FACE AND HEAD OF MAN. 



1, Common carotid ; 2, Internal carotid ; 3, External carotid ; 4, 4, Occipital 

 artery ; 5, Superior thyroid artery ; 6, Trapezius ; 7, Lingual artery ; 8, Sterno- 

 mastoid; 9, Facial artery; 10, Temporal artery, dividing into anterior and 

 posterior branches ; 11, Submental branch ; 12, Transverse facial artery ; 13, 

 Inferior labial bi*anch ; 15, Inferior coronary, and, 17, Superior coronary branch; 

 19, Lateral nasal branch; 21, Angular branch. 



INTERNAL CAROTID ARTERY. Contrary to what is observed in animals, the internal 

 carotid is a little larger than the external, a difference which is explained in Man by 



