BLOOD-VASCULAR SYSTEM, ETC., OF AMIUKUS CATUS. 425 



The subclavian arteries are the largest and most anterior pair of the 

 inter costales. They arise from the dorsal surface of the aorta descendens 

 in the groove upon the fourth vertebra, and issue by foramina be- 

 tween it and the third. They pass outwards along the anterior surface 

 of the transverse processes of the fourth vertebra beneath the strong 

 peritoneal continuation of the aponeurotic membrane. Each artery 

 gives off two branches to the muscles of this region and then turns for- 

 wards, over the head-kidney and downwards to the median spine of 

 the scapula, at which point it distributes itself. Three or four 

 branches to the anterior portion of the ventral musculature of 

 the trunk ; a branch to the pectoral fin and its muscles, which also 

 sends a strong branch backwards on the outer surface of the muscles 

 of the wall, and a branch which passes forwards beneath the girdle 

 and anastomoses with certain of the hyoidean arteries are supplied 

 by it. 



The arteries of the head have already been mentioned. It remains 

 to add a short description of their relations and distribution. 



A few small twigs arise at the junction of the branchial veins for 

 the aponeurotic wall and the fatty tissue on the base of the skull. 



An artery from the united first and second branchial veins, which 

 I shall designate as pharyngo-branchial, passes down around the 

 pharynx, which it supplies with blood, and also gives branches to the 

 posterior lev. branchiales, and in some cases the pharyngo-branchiales. 

 Small arteries for the anterior lev. branchiales arise from the first 

 branchial vein near the origin of the carotids. 



The A. car otis externa arises from the dorsal surface of the first 

 branchial vein at the angle where it turns backwards to join the 

 second. (PI. VIII. Fig. 1, c. ex). Thei-e is neither carotis commu- 

 nis nor circulus ccphalicus in Amiurus. It passes upwards over the 

 lateral surface of the N. trigeminus on to its dorsal surface and along 

 the ramus mandibularis towards the eye. A large branch supplies the 

 abductor mandibular turning backwards beneath the muscle and also 

 sending a branch through the mesethomoid bone to the nasal sac. 

 A second branch passes beneath and behind the eye, also terminating 

 at the nasal cavity. After giving a branch to the antero-lateral 

 portion of the roof of the mouth, the remainder of the artery turns 

 outwards, beneath and slightly anterior to the eye, and divides into a 

 branch to the large maxillary barblet and another to the mandible. 



