THE VASCULAR SYSTEM 25 



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121. the mandibular vein from the lower jaw. 



122. The second tributary of the precava is the innomi- 

 nate vein formed by the union of 



123. the internal jugular vein, from the dorsal portion 

 of the head, and 



124. the subscapular vein bringing blood from the dorsal 

 surface of the shoulder girdle and arm. 



125. The third tributary of the precava is the subclavian 

 vein which is formed by the union of 



126. the cutaneous vein which returns the blood distrib- 

 uted by the cutaneous artery, and 



127. the brachial vein which supplies the ventral portion 

 of the arm. // time permits, trace out the distribu- 

 tion of the subscapular and brachial veins. 



In the course of your dissection of the precaval vein, you 

 will note three small bodies which are endocrine (ductless) 

 glands. 



128. Lying next to the mesial ventral surface of the ex- 

 ternal jugular is a small reddish brown oval body, 

 the pseudothyreoid (parathyreoid) gland. 



129. Somewhat dorsal and cephalad of this, the larger 

 thyreoid gland may be seen. 



130. The thymus gland may be found by tracing the in- 

 ternal jugular to the caudal margin of the tympanic 

 membrane. 



// these bodies have been destroyed they may be observed 

 ^ later during the dissection of the muscles. 



Drawing 10. Make a sketch of the veins just dis- 

 sected. 



3. The Arteries 



Trace the arteries on the right side of the heart, commenc- 

 ing with the cut end of the truncus arteriosus. This divides 



