404 DISSECTION OF THE PIGEON 



to supply the flexor muscles of the thighs, and 

 the muscles of the legs. 



Each sciatic artery gives off a middle 

 renal artery to the middle lobe of the kidney, 

 and a posterior renal artery to the posterior 

 lobe. 



vi. The posterior mesenteric artery is a median 

 vessel, which arises opposite the hinder ends 

 of the kidneys, and supplies the rectum and 

 cloaca. 



vii. The internal iliac arteries are a pair of vessels 

 arising about the same level as the posterior 

 mesenteric artery, and running outwards 

 and backwards along the hinder part of the 

 pelvis. 



viii. The caudal artery is the terminal portion of 

 the dorsal aorta, which runs along the ventral 

 surface of the caudal vertebrae. 



D. Dissection of the Heart. 



The heart may be dissected in situ, or the vessels may be 

 cut across about a quarter of an inch from it, and the heart 

 removed and placed in a dissecting -dish under water. 



I. The auricles. 



Slit up the outer walls of the two auricles with scissors ; 

 arid wash out the contained blood. 



a. The right auricle. 



i. The openings of the venae cavae. 



Pass a seeker into these, and note their positions relatively 

 to the cavities of the heart. 



ii. The Eustachian valve is a muscular fold, pro- 

 jecting into the cavity of the auricle, on the 

 right side of the opening of the posterior vena 

 cava. 



iii. The septum auricularum is a thin muscular 

 on, dividing the right and left auricles 



