208 THE OAT. [CHAP. vn. 



The second and much smaller vessel given off from the arch of the 

 aorta, is the root artery of the arteries of the left fore-limb i.e., it 

 is the left sub-clavian artery (si). After giving this off, the aorta 

 passes upwards as the thoracic part of the great dorsal (in man, the 

 " descending") aorta. It gives off a number of branches, which 

 will be referred to shortly. 



16. The two CAROTID ARTERIES pass forwards along the neck, 

 one on the right and the other on the left side of the trachea and 

 oesophagus, to the head. Each gives off in succession the following 

 branches : Each gives off a rather large artery to supply the muscles 

 of the side of the neck ; and, opposite to this, a small branch to the 

 lymphatic gland lying on the middle of the trachea. Next comes the 

 thyroid artery, which goes to the thyroid cartilage, and to a structure 

 to be hereafter described as the thyroid gland. It then gives off (from 

 its opposite side) another artery to the muscles of the neck, and (almost 

 opposite this) a very large lingual artery, which passes dorsally to the 

 basi-hyal, beneath the stylo-glossus, and goes to the under surface of 

 the tongue. The carotid next gives off a small facial artery, which 

 sends out branches to the cheek, and ends in the upper and lower 

 lips. A small branch goes to the sub-maxillary gland, starting 

 from the very root of the facial artery. The carotid artery then 

 makes a sharp bend, and gives off backwards a branch to the 

 parotid gland ; and then, at the further end of the curve, another 

 branch, which also goes in part to the parotid gland, and a part to 

 the muscles of the temporal fossa. This arched part of the carotid 

 ends anteriorly, close to the anterior margin of the glenoid surface. 

 The carotid then breaks up into a plexus of minute branches, which 

 run side by side under the eye-ball, and over the orbital plate of the 

 maxilla. From this plexus minute arteries are given off, such as 

 the ophthalmic, ciliary, ethmoidal and meningeal arteries. 



The ophthalmic artery passes along the inner side of the orbit, 

 giving off branches to the lachrymal gland, the forehead and muzzle, 

 the eye-ball and nasal cavity, the latter being called the ciliary and 

 ethmoidal arteries. 



The meningeal artery supplies the dura mater. It enters the 

 skull from the plexus, through the sphenoidal fissure. 



The nasal artery is a small branch which passes through the 

 spheno-palatine foramen (in company with the nasal nerve), and 

 continues on, skirting the nasal septum. 



The carotid also gives off the superior dental artery, which enters 

 the maxilla posteriorly, and supplies the upper teeth. Finally, the 

 carotid passes through the infra-orbital foramen, and terminates as 

 the infra-orbital artery, which distributes its branches about the 

 face. 



A very minute vessel, called the internal carotid, is given off 

 from the main carotid in the vicinity of the foramen lacerum 

 posterius. It enters that aperture, and passes along a slender canal 

 between the basi- occipital and basi-sphenoid, and the adjacent part 

 of the temporal bone. It then enters the cranial cavity on the 



