198 THE SALAMANDER 



After turning anteriorly the carotid artery passes along the lateral 

 border of the thyroid gland to which it sends : 



(ii) The thyroid artery — a short but fairly broad vessel which breaks 

 up immediately within the gland into a rich network. 



On reaching the level of the second hypobranchial cartilage the 

 main artery divides into three (sometimes four) branches as follows : 



(iii) The sublingual artery (a.subl.), the more superficial of the two 

 anterior branches, passes along the lateral border of the geniohyoid 

 muscle to within about 3 mm. from the tip of the lower jaw. Here it 

 divides into four rami. 



(a) R. Ungualis which passes mesially and enters the tongue 

 together with the hypoglossal nerve. 



{¥) R, muscularis which passes anteriorly and enters the M. genio- 

 glossus. 



(c) R. communicans which passes laterally and sends a branch to 

 the M. subhyoideus, then turning anteriorly and passing to the 

 middle line round the lower jaw, where it may fuse with its fellow on 

 the other side, although it may also anastomose with the mandibular 

 artery. Whether these anastomoses always occur is uncertain, since 

 failure to find them in every case may rather be due to faulty in- 

 jections than to the absence of the vessels. They are very fine vessels. 



{d) R. intermandihularis arises soon after the origin of the sub- 

 lingual artery at the level of the first hypobranchial cartilage and 

 passes ventrally into the underlying muscle of the same name. 



(iv) The lingual artery (a. ling.), the other anterior branch, runs more 

 or less parallel with the previous artery but deep to the geniohyoid 

 muscle. It enters the tongue at two or three points between the 

 radials of the copula, i.e. together with the glossopharyngeal nerve. 



(v and vi). Two muscular branches which pass laterally to the 

 lateral edge of the M. subarcualis rectus I, which they supply. These 

 two branches may be represented at their origin by a single vessel for 

 a greater or shorter distance. 



All the branches of the external carotid artery are somewhat con- 

 voluted and very extensible — a necessary feature in view of the large 

 amount of movement to which the parts they supply are subjected. 

 They are only loosely held by connective tissue and are easily dis- 

 sected. The external carotid artery as a whole has been called the 

 Arteria lingualis by some authors — e.g. Hoffmann — but this would 

 seem to be a misnomer. 



B. The internal carotid artery (PL XIII, fig. 58 ; PI. XIV, fig. 6 1) 

 (a.car.i.) continues the direction of the common carotid as far as the 

 floor of the otic capsule. Here it divides, giving off the A. petrosa 



