THE VASCULAR SYSTEM 199 



lateralis (a.pet.l.) (Driiner), which turns dorsalwards around the 

 posterior border of the processus basilaris and enters the antrum 

 petrosum laterale by the 'faciaHs' opening (see below). The remain- 

 ing branch of the internal carotid then bends somewhat mesially 

 across the ventral face of the Proc. basilaris and enters the carotid 

 canal (Fig. 2, can. car.) — a groove in the floor of the cranium covered 

 ventrally by the parasphenoid bone. There is no definite 'carotid 

 foramen' in the Salamander's skull. The artery enters the cranial 

 cavity through the hasicranial fenestra and immediately gives ofl^ the 

 A. carotis cerehralis (a.car.ce.) (Scholb.) — see 'Vessels of the Brain'. 



The remainder of the vessel turns anteriorly along the edge of the 

 basicranial fenestra as far as the foramen for the N. oculomotorius. 

 It then penetrates this foramen and passes into the orbit as the A. 

 ophthalmica (see next page). 



(i) A. petrosa lateralis (Driiner) (a.pet.l.). This small but important 

 vessel is probably to be regarded as the homologue of the stapedial 

 artery of Mammals. As already described it passes into the antrum 

 peirosum laterale around the posterior border of the processus basi- 

 laris, mesial to the corresponding vein, and ventral to the columella. 

 Within the antrum the artery loops over the dorsal edge of the vein 

 so as to lie lateral to it. It leaves the antrum between the Proc. 

 oticus and the Proc. ascendens together with the mandibular and 

 maxillary branches of the Vth nerve, and divides into the following 

 two main branches: 



{a) A. temporalis (a.t.), which accompanies the second division of 

 the trigeminal nerve to the posterior angle of the eyelids, and here 

 divides into two equal branches, one of which, the superior orbital 

 artery^ passes around the upper eyelid and anastomoses with the R. 

 ophthalmicus superior posterior of the A. ophthalmica. The other 

 turns ventrally and supplies the lower eyelid and the tissues of the 

 posterior end of the upper jaw, and represents a portion of the inferior 

 orbital artery (a.o.i.), the other part being represented by a branch of 

 the A. mandibularis. 



{F) A. mandibularis (a.m.). This branch of the A. petrosa lateralis 

 turns ventralwards and accompanies the mandibularis branch of the 

 trigeminus. Very soon after its origin it gives off a branch anteriorly, 

 which passes through the levator mandibulae muscle and is dis- 

 tributed to the roof of the mouth at the postero-ventral corner of the 

 orbit and also to the inflected portion of the skin which occurs in the 

 coronoid region. This branch has not always been found, but failure 

 to find it is more probably due to faulty injections than to its absence. 

 It is very easily damaged in removing the muscle through which it 



