170 ZOOTOMY. 



the left crosses over to the right side to join its fellow at 

 about the level of the origin of the cceliaco-mesenteric 

 artery : each trunk receives renal veins from the corres- 

 ponding kidney, and unites with its fellow just anterior to 

 the bifurcation of the caudal vein. 



183. The femoral artery (/.a), passing outwards to 

 the hind limbs between the femoral and sciatic veins : its 

 origin from the dorsal aorta is best seen at a later stage. 



XX. Cut through the stomach a short distance behind 

 the heart, and through the rectum a little anterior 

 to its junction with the cloaca, and remove the 

 alimentary canal between these two points : open 

 the various parts of it by longitudinal incisions, 

 and note 



184. The rugae of the stomach, strong longitudinal ridges 

 into which its mucous membrane is produced, and the 

 pyloric valve, an annular ridge of mucous membrane 

 narrowing the aperture between the stomach and duodenum. 



185. The valvulae conniventes, delicate longitudinal 

 ridges on the mucous membrane of the small intestine. 



1 86. The ileo-caecal valve, an annular ridge of 

 mucous membrane narrowing the aperture between the 

 small and large intestines, and projecting into the latter. 



187. The aperture of the bile-duct in the duodenum. 



XXI. Dissect away the peritoneum from the kidneys 

 and reproductive organs, and open the cloaca by 

 a ventral longitudinal incision a little to one side 

 of the middle line, so as not to injure the bladder. 

 Make out 



1 88. The division of the cloaca by an incomplete ridge 

 of mucous membrane (Figs. 41 and 42, r) into two sections, 

 an anterior (cl l ) receiving the rectum and a posterior (d' 1 ) 

 opening externally by the vent. 



