112 THE FROG, OR THE TOAD. 



the small intestine immediately following the stomach is the 

 duodenum. There is no external line of division to separate it 

 from the rest of the intestine. Find the place where it is entered 

 by the bile duct. 



e) The coils of the intestine are held together and the whole tract sus- 



pended from the roof of the abdominal cavity by a fold of the 

 peritoneal lining called the mesentery. In the web of mesen- 

 tery between stomach and duodenum is a light colored gland, the 

 pancreas. Farther back along the tract is the small, dark, 

 roundish spleen. 



Exercise 5. Make a diagram of the digestive tract, including liver spleen, 

 and pancreas. 



.Exercise 6. Make a diagram of the heart, including the two main arterial 

 trunks and the stubs of their first three branches. 



f) Lift the lobes of the liver to expose the lungs. These are pinkish 



organs each looking somewhat like an elongated strawberry. 

 Thrust a blowpipe into the glottis and inflate them. How they 

 swell out! Correlate this expanded condition with the act of 

 floating. Tie a string around the neck of one of the lungs when 

 inflated, cut the latter off above this point and lay it aside to dry. 

 You will then observe that it is not a mass of spongy tissue, but a 

 simple, hollow sack. The lungs are so close to the glottis that 

 there is no need of an air tube or trachea. There is, however, 

 a short laryngo-tracheal chamber stiffened by cartilage and con- 

 taining the vocal chords. 



g) Lying ventrally to the rectum is the large, thin-walled urinary 



bladder. It is probably empty and may be difficult to distin- 

 guish. If so, try inflation with a blowpipe inserted in the anus. 

 The urinary bladder is connected by a small opening with the 

 cloaca or posterior division of the alimentary tract. Into this 

 vestibule open also the tubes from the reproductive and renal 

 organs. 



h) Remove the organs so far studied, saving the stomach for an 

 examination of its contents. The numerous finger-like masses of 



