348 ANATOMICAL TECHNOLOGY. 



with plaster, and after the plaster was moderately hard, a hemi- 

 section of the vessel was made and the plaster removed. 



Explanation of Fig. 102. — Arcus aorticus, az. — The arch of the aorta. A. brcph., 

 A. brachio-cephalica, az. — The brachio-cephalic or innominate artery. A. crd. dext., 

 A. cardiaca dextra — The right cardiac or coronary artery. A. crd. sin., A. cardiaca 

 sinistra — The left cardiac or coronary artery. A. mdst., A. mediastinalis, az. — The 

 mediastinal artery. A. sbclv. dext., A. subclavia dextra — The right subclavian artery, 

 a continuation of the brachio-cephalica. A. carotidea sin. (sinistra) — The left carotid 

 artery arising from the brachio-cephalica ; see A. A. vertebralis — The vertebral artery. 

 This arises from the subclavian. A. cstl. (costalis) superior — The superior costal artery. 

 A. strn., A. sternalis — The sternal or internal mammary artery. A. axillaris — The 

 axillary artery. A. thr. ant., A. thoracica anterior — The anterior thoracic artery. 

 A. thr. (thoracica) longa — The long thoracic artery. A. subscapularis — The subscap- 

 ular artery. A. circumflexa — The circumflex artery ; a common trunk arising from the 

 axillary bifurcates to form this and the preceding artery ; in man they arise separately 

 from the axillary. A. brachialis — The brachial artery. A. radialis — The radial arteiy. 

 A. ulnaris — The ulnar artery. A. interos., A. interosseus — The interosseus artery. 

 Costa (1) — The first rib in cross section. Fm. eptrch.. Foramen epitrochleare. VI. 

 semilunares — The semilunar valves at the beginning of the aorta ; they are closed. 



Explanation of Fig. 102, A.— Aorta, az, A. brcph., A. brachio-cephalica, az.— 

 The brachio-cephalic artery. A. sbcl., AA. subclaviae — The subclavian arteries. A. c. 

 dext., A. carotidea dextra. A. c. sin., A. carotidea sinistra. 



The carotids may arise separately from the brachio-cephalica as shown in Fig. 102, or 

 less frequently they may arise by the bifurcation of a single trunk which is given off from 

 the brachio-cephalica (Fig. 102, A). This common trunk is called by Owen (A, III, 535), 

 the Ucarotid, and by Milne-Edwards (A, III, 524), carotide primitive. It is stated by the 

 latter that this is the normal condition in the cat, lion, dog, etc. 



Fig. 102, B. — Vein slit lengthwise and spread out to show two pairs of valves. 



Fig. 102, C. — Hemisection of a vein with closed valves. 



In both B and C the central end is uppermost. C shows how the two valves pre- 

 vent the flow of blood or injecting mass toward the periphery. Sometimes but a single 

 valve exists, in which case the action is less efficient. 



§ 918. Posture and Exposure for the Thoracic Vessels. — Place 

 the cat dorsicumbent, with the arms stretched laterad and fastened 

 with cords to the loops in the edge of the tray (Fig. 76). If the dis- 

 section is to be long continued, the caudal half of the body may be 

 removed (§ 234). 



Commence on the right side, and continue the incision made in 

 exposing the Y. jugularis for injection (§ 913) to a point opposite 

 the base of the xiphisternum, carrying the incision 2 cm. to the 

 right of the ventrimeson ; then, with the arthrotome, cut through 

 the sterno-mastoid and pectoral muscles (Fig. 72), along a line about 

 2 cm. to the right of the ventrimeson and parallel with it. Cut 



