246 VERTEBRATES. 



tion and its great size. It is a sort of food reservoir, 

 It ends blindly in a narrow, thick-walled, finger-shaped 

 process (the vermiform appendage). 



The large intestine completes the alimentary canal. It 

 is distinctly sacculated at its anterior end, becoming 

 smooth posteriorly. 



These organs can be freely examined in place. Their 

 attachments should not be severed until after the blood 

 vessels have been studied. 



The spleen is a dark-red body lying behind the stomach, 

 and attached to its left end. 



Renal Excretory System. A pair of compact, brown- 

 ish, bean-shaped kidneys lie closely attached to the dorsal 

 wall of the abdominal cavity. Notice that the right one 

 is anterior to its fellow. Observe a large artery entering, 

 and a large vein leaving, each kidney. Observe also a 

 long white duct (a ureter) extending posteriorly from 

 each kidney, to open into the urinary bladder, a whitish 

 membranous sac lying ventral to the posterior end of the 

 large intestine. Associated with the afferent duct of the 

 bladder are the passages from the reproductive organs; 

 and the external aperture for these is separate from the 

 anal aperture. 



The Circulatory System is very similar to that of a bird. 

 The heart is four-chambered, consisting of right and left 

 auricles and ventricles. The boundaries of these cham- 

 bers are evident from the outside ; but the heart should be 

 dissected later, to show the relative thickness of the walls 

 of these chambers, and the valves, which prevent the 

 return of blood at the entrance to the ventricles and to 

 the aorta. 



I. The Venous System. The blood is brought to the 

 heart through right and left prcecavce and the single 

 large postcava. These three vessels enter the right 



