350 ANATOMICAL TECHNOLOGY. 



the Y. vertebralis the Y. bracMo-cephalica is formed by the umon 

 of two nearly equal branches, the subclavian vein and the external 

 jugular. The V. subclavia may be traced to the arm. Later, 

 in studying the arteries of the arm, it will be found to follow them 

 very closely. 



§ 925. V. jugularis externa (Fig. 87, 101, 103, A).— This large 

 vein comes from the head and face. In the neck it is covered only 

 by the skin and cutaneous muscle. Opposite the cephalic part of 

 the larynx there is a very large branch connecting the jugulars of 

 the two sides (Fig. 101, Y. trns.). 



The external jugular receives the internal jugular (Fig. 101, V. 

 jgl. int.), the combined trunk of the subcutaneous vein of the arm 

 and the V. subscapularis. This trunk is shown in Fig. 101 just 

 cephalad of the abbreviation Y. Jgl. int. 



Yeins of the Abdomen, see §§ 946-964. 



ARTERIES OP THE THORAX AND ARM. (See Table, § 916.) 



§ 926. Aorta thoracica, az. (Fig. 91, 99, 100, 101, 102, 103, 107). 

 —The aorta is the single great artery arising from the left ventricle 

 of the heart. Through it and its branches, every part of the body 

 is supplied with pure blood. To expose it, remove the pericardium 

 from the ventral wall of the heart, also the preecava, the septum 

 mediastinale, and the thymus body if that is present. The aorta 

 curves sharply to the left (Fig. 102), thus making the arcus aorti- 

 cus. The branches of the thoracic aorta are as follows, commencing 

 centrad : — 



AA. cardiacse s. coronariae (see § 856). 



§ 927. A. brachio-cephalica s. innominata, az. (Fig, 101, 102, 

 103, 107). — This arises from the convexity of the aortic arch and 

 passes almost directly cephalad. Very near its origin it gives rise 

 to the A. mediastinalis, which passes ventrad, then to the A. ca- 

 rotidea sinistra (Fig. 101, 102, 102, A, 103, A, C, and 107), and 

 the A. carotidea dextra. Sometimes the two carotids arise as a 

 single trunk (Fig. 102, A). After the origin of the carotids, the 

 A. brachio-cephalica is continued as the A. subclavia dextra (§ 933). 



§ 928. A. subclavia sinistra (Fig. 101, A. sbclv., 102, 103, A. 

 sbclv. sin., 107, A. s.).— For the branches of the A. subclavia, see 

 §§ 934-945 and the Table (§ 916). 



