THE GARDEN TOAD 9 



of the stomach in the mesentery an irregular pinkish 

 glandular structure which leads by a small duct into the 

 intestine. This gland is the pancreas, and the duct is 

 the pancreatic duct. From it comes a secretion which 

 aids in the digestion of food. Near the upper end of the 

 pancreas note a round nodular structure, generally dark 

 red. This is the spleen, a ductless gland, the use of 

 which is not altogether known. 



Make a drawing which will show as many of the organs 

 noted as possible. 



TECHNICAL NOTE. Pass two pieces of thread under the rectum 

 near the pubic bone. Tie these threads tightly a short distance 

 apart and then cut the rectum in two between the threads. Now 

 carefully lift up the alimentary canal with attached organs (liver, 

 etc.), and cut it off near the region of the heart. 



How is the heart situated with regard to the lungs ? 

 The heart consists of a lower chamber with thick muscular 

 walls, the tip, called the ventricle, and two upper thin- 

 walled chambers, the right and left auricles. Can you 

 make out these three chambers ? The purified blood from 

 the lungs flows into the left auricle, while the venous 

 blood from all over the body laden with its carbon dioxide 

 enters the right auricle. From these two chambers the 

 blood enters the ventricle. Here the pure and impure 

 blood are mixed. From the ventricle the blood enters a 

 large muscular tube on the ventral side of the heart. This 

 is the conus arteriosus, which gives off three branches on 

 each side ; the anterior ones, the carotid arteries, supply 

 the head, the next ones, the systemic arteries, or aortce, 

 carry blood to the rest of the body, while the posterior 

 vessels, the pulmonary arteries, go directly to the lungs 

 and there break up into fine vessels (capillaries) where 

 the carbon dioxide is given off and oxygen is taken from 

 the air. From the lungs the blood returns through the 

 puhnonary vein to the left auricle. Meanwhile the blood 



