48 ANATOMY OF A CHELONIAN. 



off a large branch (inferior mesenteric) to the colon, and 

 the right a much smaller twig to the rectum ; the trunks 

 then proceed to the pelvis and are distributed to the 

 penis or clitoris. 



113. Each external iliac passes outward and back- 

 ward, and divides into — 



a. A branch distributed to the muscles of the 

 pelvis and the inner aspect of the thigh. 



b. The sciatic artery, which supplies most of the 

 lower limb. It takes a more dorsal direction 

 than a, and approaches the carapace in the 

 region of the sacral vertebrae, there coming 

 into relation with the sciatic nerve. Giving off 

 in this region a small branch, the artery turns 

 outward with the nerve, and the two (passing 

 on the mesial side of the ilium) reach the back 

 of the leg, where they may be found and traced 

 in their further distribution by dividing the 

 skin and subcutaneous tissue along a line 

 drawn from the inner side of the dorsal end 

 of the ilium to the outer side of the knee-joint. 



114. Clean and trace the pulmonary artery ; immedi- 

 ately after springing from the ventricle it divides into 

 a right and left branch. The right passes dorsally to all 

 the other trunks proceeding from the ventricle on the 

 right side of the heart, and is found lying posterior to, 

 and parallel with, the right aorta for some distance ; 

 it then crosses ventrally to this vessel and enters the 

 lung. The left pulmonary artery runs forward and 

 outward to its lung. 



115. Trace the pulmonary veins, one from each lung, 



