8 ELEMENTARY ZOOLOGY 



vessels. This is followed by a relaxation of the apex and 

 a contraction of the basal portion, the auricle. 'The heart 

 is surrounded by a delicate semi-transparent sac, the 

 pericardium. The' pericardium is filled with a watery 

 fluid, body-lymph, which bathes the heart. Note between 

 the lobes of the liver a small bladder-shaped transparent 

 organ of a pinkish color. This is the gall-cyst, or gall- 

 bladder, a reservoir for the bile, the secretion from the 

 liver. Separate the lobes of the liver and note, beneath, 

 the long convoluted tube which fills most of the body- 

 cavity. This is part of the alimentary canal. Is the 

 alimentary canal of uniform character ? The most anterior 

 portion of the canal, the gullet or cesopJiagus, leads to a 

 large U-shaped enlargement, the stomach. From the lower 

 end of the stomach there extends a long, slender, very 

 much convoluted tube, the small intestine, which is fol- 

 lowed by a much larger one, the large intestine. This large 

 intestine after one or two turns passes directly back into 

 the rectum, which opens at last to the exterior through the 

 anus. Note just ventral to the rectum a large thin-walled 

 membranous sac. This is the urinary bladder which acts 

 as a reservoir for the secretion from the kidneys. Notice 

 a many-branched yellow structure with a glistening 

 appearance, the fat-body (corpus adiposuui). Now push 

 liver and intestine to one side and note the pinkish sac-like 

 bodies (perhaps filled with air), the lungs. The lungs are 

 paired bodies which open into the laryngo-tracheal cham- 

 ber. The toad takes air into its mouth through its 

 nostrils, and then forces it, by a kind of swallowing action, 

 through the laryngo-tracheal chamber into the lungs. 



Now lift the stomach and note in the loop between its 

 lower end and the small intestine a thin transparent tissue. 

 This is a part of the mesentery, which will be found to 

 suspend the whole alimentary canal and its attached 

 organs to the dorsal wall of the body. Note in the loop 



