576 THE ARTEE1ES. 



and the rectus anticus major; outwardly, to the scalenus, towards the 

 inferior extremity of the neck, and to the subscapulo-hyoideus, which 

 separates the artery and jugular vein in the middle and superior part. But 

 near the entrance to the chest, these two vessels are in direct relationship, 

 the vein below and the artery above. 



It is also to be noted, that the glands at the entrance of the chest are in 

 contact with the carotids, and that the left artery corresponds, besides, to 

 the oesophagus. 



COLLATERAL BRANCHES. The branches furnished by the common carotid 

 on its course are somewhat numerous, but they are of such inconsiderable 

 diameter that their successive emission does not sensibly vary the calibre 

 of the vessel from which they emanate ; so that the carotids represent, from 

 their origin to their termination, two somewhat regular cylindrical tubes. 

 These collateral branches are destined either to the muscles of the cervical 

 region, or to the oesophagus and trachea. Two of them, the thyro-laryngeal 

 and accessory thyroid arteries, will occupy us in a special manner. 



THYRO-LARYNGEAL ARTERY (Fig. 282, 14"). This vessel, which corre- 

 sponds exactly to the superior thyroid artery of Man, 1 arises from the 

 common carotid at a short distance from its termination, a little behind the 

 larynx or above the thyroid body ; it passes on that organ, into which it 

 enters by two principal branches that turn round its superior extremity and 

 anterior border, after sending two branches to the larynx a superior, des- 

 tined also to the pharyngeal walls ; and an inferior, much more considerable, 

 which is exclusively distributed to the laryngeal apparatus. 



It sometimes happens that the thyro-laryngeal artery is found divided 

 from its origin into two quite distinct branches, each furnishing a laryngeal 

 and a thyroid division, as in figure 286, 3. 2 



We have already remarked the disproportion that exists between the 

 considerable calibre of the branches sent by this artery to the thyroid body, 

 and the slender volume of that organ ; so that it will at present suffice to 

 remind the student of this peculiarity. 



ACCESSORY THYROID ARTERY (Figs. 282 14' ; 286, 2). The origin of 

 this vessel precedes that of the first ; it is much smaller, and enters the 

 thyroid body by the posterior or inferior extremity of this glandiform 

 lobe. 



This artery often sends only some excessively fine ramuscules to the 

 thyroid gland, and expends itself almost entirely in the cervical 

 muscles. 3 



TERMINAL BRANCHES. The three branches which terminate the common 

 carotid are the occipital, and internal and external carotid arteries ; the latter 

 is incomparably larger than the other two, which only appear to be collateral 

 twigs from the principal vessel. It is these branches which distribute the 

 blood to the various parts of the head. We will devote three special 

 paragraphs to their study ; but their preparation will previously demand 

 some notice. 



1 We would have given it the same name if we could have found the true repre- 

 sentative of the inferior thyroid artery. 



2 It was doubtless a case of this kind that Rigot had before him when he described 

 the above vessel, and made two arteries of it the thyroid and laryngeal. But, we 

 repeat, this example is only exceptionally met with, and does not authorize its being 

 supposed to be the rule, and cause the creation of a distinct thyroid and laryngeal artery; 

 since each branch of the vessel is distributed to the larynx and thyroid body at the 

 same time. 



* We regard it as the analogue of the middle thyroid of Man. 



