144 DEVELOPMENT OF AETERIES IN FORELIMB OF PIG. 



atlantal region and anastomoses with the occipital. The vertebral artery begins 

 opposite the first intercostal space, from the brachiocephalic trunk on the right, 

 from the subclavian on the left. It passes upwards and forwards, on the left cross- 

 ing the esophagus, on the right the trachea. The deep cervical branch, smaller than 

 the dorsal, emerges through the first intercostal space, gives off the intercostal 

 artery, and then ramifies in the muscles of the neck. The inferior cervical artery 

 is large and gives off branches to the thyroid and to the parotid. The internal 

 mammary is large. 



The subclavian is continued over the first rib into the forelimb. The brachial 

 gives off the subscapular, the anterior and posterior circumflex and branches to 

 the deltoid, corresponding to the thoracic axis in the human anatomy. In the arm 

 the brachial gives off a large branch which follows the radial nerve (a superior pro- 

 funda) and in the neighborhood of the elbow a branch following the ulnar nerve 

 (inferior profunda). 



The brachial is continued into the forearm, as the arteria mediana, in relation 

 with the median nerve between the superficial and deep tendons. It breaks up 

 into branches for the four digits, which branches communicate with the dorsal 

 digital branches. Halfway along the forearm the arteria mediana gives off a slender 

 radial artery which continues to the radial side of the radial digit. It forms, with 

 the median artery, a representation of a superficial palmar arch. It also gives off 

 a dorsal branch which communicates with the dorsal interosseous artery and con- 

 tributes to the dorsal digital supply. From the arteria mediana arises an ulnar 

 artery, which is small and which soon breaks up into a capillary network. This 

 capillary network communicates with the arteria mediana and with the volar inter- 

 osseous artery and thus is represented a deep palmar arch. The volar interosseous 

 from the median artery lies between the radius and ulna and communicates with a 

 recurrent branch of the median artery and with the ulnar. Its main continuation 

 is by way of a dorsal branch which reaches the dorsum of the hand between the 

 two bones of the forearm. The dorsal interosseous arises from the arteria mediana 

 by way of the common interosseous and soon becomes reduced. It communicates 

 with the dorsal continuation of the volar interosseous. 



