CIRCULATORY SYSTEM. 189 



and is dispersed upon the membrane lining the larynx : in some 

 instances, however, this forms a branch of the main trunk. The 

 common division of the carotid is into the three vessels just 

 named ; but not infrequently we meet with a fourth coming from 

 the point of ramification, the additional one being the facial artery; 

 and, occasionally, we only find a simple bifurcation of the vessel 

 into the external and internal carotids. 



The External Carotid Artery 



Is the large division, the one that looks like the continuation 

 of the trunk of the common carotid itself. It takes a flexuous 

 course : first it curves downward behind the angle of the jaw, 

 where it crosses the insertion of the stylo-maxillaris, by which it 

 seems defended from injury; next it makes a curve upward and 

 forward, crosses the membranous sac of the fauces, and passes 

 between the stylo-maxillaris and cornu of the os hyoides, deeply 

 buried under the parotid gland ; lastly, it makes a third curve, 

 directing it forward along the posterior border of the branch of the 

 jaw, and to that it subsequently corresponds in its course until it 

 bifurcates, which it does immediately behind the neck of the con- 

 dyle. This vessel is so bedded in glandular substance, surround- 

 ed by venous and nervous trunks, and protected by neighbouring 

 bony prominences and muscles, that but a small, and that the 

 upper, portion of it is safely accessible to the knife : rather 

 more than an inch below and behind the condyle, it is com- 

 paratively superficially lodged, being there only covered by the 

 anterior thin border of the parotid and a thick aponeurosis, in 

 addition to the common integuments. We reckon eight branches 

 from it. 



1. Submaxillary artery: it comes off behind the cornu 

 of the OS hyoides, just as the vessel is going to make its second 

 curve, and ranks next in size to the carotid itself. It takes an 

 oblique course downward and forward within the submaxillary 

 space, preserving at first the line of the cornu ; afterwards it 

 crosses the lower portion of the pterygoideus, and reaches the 

 posterior border of the branch of the jaw (about one-third of its 

 length downward), round which it turns to mount upon the face: 

 in making this turn it becomes subcutaneous, distinctly per- 

 ceptible to the feel, and (from being in contact with the bone) 

 very conveniently compressible, on which account, it is the vessel 

 ordinarily selected to convey a knowledge of the state of the pulse. 

 In ascending upon the face, it corresponds to the anterior border 

 of the masseter; but before it reaches the alveolar processes it 

 ends, by a pretty equal division, in the /ir/c/rt/ and inferior labial 



