736 CIRCULATORY SYSTEM OF THE PIG 



The Arteries 



The pulmonary vessels present no remarkable features. 



The aorta resembles that of the horse and ox in its course and relations, but the 

 arch is much more strongly curved. There is no common brachiocephalic trunk. 



The brachiocephalic artery arises first from the aortic arch and passes forward 

 below the trachea to the first rib. Here it gives off the common carotid arteries, 

 separately or by a very short bicarotid trunk, and is continued around the first rib 

 as the right brachial artery. 



The left brachial artery arises from the aortic arch just above the brachio- 

 cephalic. It curves forward and doAATiward and turns around the anterior border 

 of the first rib. 



The branches given off by the brachial arteries are as follows: 



There is usually a common trunk for the dorsal, deep cervical, and vertebral 

 arteries. This trunk or the dorsal artery gives off the subcostal artery, which sup- 

 plies usually the third, fourth, and fifth intercostal arteries. The second inter- 

 costal artery arises separately. The dorsal artery emerges through the dorsal end 

 of the second intercostal space and divides into dorsal and cervical branches ; the 

 dorsal branch passes upward and backward and ramifies in the deep muscles of the 

 anterior part of the back ; the cervical branch passes deeply to the atlantal region, 

 where it anastomoses with the occipital artery. The deep cervical artery is a 

 much smaller vessel, which emerges through the first intercostal space; it gives off 

 the first intercostal artery, passes upward and forward deeply, and ramifies chiefly 

 in the complexus and multifidus. The vertebral artery resembles that of the horse. 



The inferior cervical artery is large ; its ascending branch gives off the posterior 

 thyroid artery and parotid branches. 



The internal and external thoracic arteries give branches to the pectoral 

 mammary glands; the external artery may be absent. 



The common carotid arteries arise from the brachiocephalic close together or 

 by a very short common trunk; they are accompanied by an internal jugular vein 

 of considerable size, and their collaterals are similar to those of the horse. They 

 terminate in occipital and internal and external carotid divisions. 



The occipital artery resembles that of the horse. 



The internal carotid artery usually arises by a common trunk with the occipital. 

 After giving off a large meningeal branch which enters the cranium through the 

 mastoid foramen, it passes through the foramen lacerum and forms with the oppo- 

 site artery a rete mirabile which resembles that of the ox, but is smaller; it is not 

 connected with the vertebral and condyloid arteries, but the meningeal branch just 

 mentioned and the middle meningeal artery concur in its formation. 



The external carotid artery has the same course and termination as in the horse. 

 Its collateral branches present the following special features: (1) The lingual 

 artery is relatively large and supplies the pharyngeal artery, the sublingual artery, 

 muscular branches, and branches to the soft palate, mandibular gland, and larynx. 

 (2) The external maxillary artery is represented by a small vessel which ends in the 

 masseter muscle; it gives branches to the pterygoideus medialis, the parotid and 

 mandibular glands, and the mandibular lymph glands, the masseter and the cuta- 

 neus. It does not extend upon the lateral surface of the face. (3) The posterior 

 auricular artery is long and relatively large ; it ascends along the anterior border of 

 the paramastoid process and ramifies on the convex surface of the external ear. It 

 gives off the posterior meningeal artery, which enters the cranial cavity through the 

 mastoid foramen. 



The internal maxillary artery pursues a flexuous course between the ramus of 

 the mandible and the pterygoid muscles to the maxillary recess and divides into 

 infraorbital and palatine branches. Its branches offer the following special features: 



