V£INS OF THE THORAX. 349 



the thoracic wall on the right side at the junction of the rihs and 

 their cartilages, and then across the meson (Pig. 76, § 825) ; do this 

 with either the arthrotome or bone scissors. Then cut with nippers 

 the right ribs about 2 cm. from their heads. Turn the sternum to 

 the left and the wall of the thorax to the right. This will expose 

 the heart, right lung, prsecava, the abdominal part of the postcava, 

 the right carotid and sternal arteries, and the axillary vessels and 

 nerves (Fig. 101, 105). 



VEINS OF THE THORAX. (See Table, § 914.) 



W. cardiacse s. coronarise (see § 887). 



§ 919. Praecavar az., and its branches (Fig. 101).— The prsecava 

 is the prominent vessel extending from a point opposite the first 

 rib to the cephalic part of the right auricle of the heart. It is 

 noticeable just at the right of the meson. 



§ 920^ V. azygos, az. (Fig. 99, 101, 107, V. az.).— This enters the 

 prsecava just cephalad of the root of the right lung. Grasp the right 

 lung and turn it toward the left, and with the tracer follow the 

 V. azygos peripherad. At regular intervals branches from the 

 intercostal spaces enter it. Those entering it near its termination 

 are large, as they represent the trunk formed by the union of two 

 or more intercostal veins. Opposite the 10th rib the vein becomes 

 mesal in position, and is dorsad of the aorta (Fig. 107, V". az.). The 

 V. azygos can not be traced caudad of the diaphragm. 



§ 921. v. sternalis (Fig. 101, V. stm., 99, 100).— About opposite 

 the 3d rib the sternal veins enter the prsecava as a single trunk, but 

 on the sternum there are two veins, one on each side just mesad 

 of the corresponding artery. 



§ 922. V. brachio-cephaUca s. iimominata (Fig. 101, 103, 107, 

 V. brcph.).— If the thymus body is present, separate it from the 

 prsecava. About opposite the 1st rib the prsecava will be seen to 

 be formed by the union of two nearly equal branches, the VV. Ira- 

 cMo-cephalicce. Carefully isolate the right one. 



§ 923. V. vertebralis.— Very near the 1st rib this large branch 

 enters the dorsal side of the brachio-cephalica. It comes from the 

 brain through the vertebrarterial canal in connection with the ver- 

 tebral artery (Fig. 104, A. vrt.). 



§ 924. v. subclavia (Fig. 101).— Just beyond the entrance of 



