86 Practical Zoology. 



breathing on it? Touch it with the point of the forceps. Does 

 this affect it? 



4. Push the liver to the right and expose the pale stomach. 

 Use the blowpipe as a probe and push it back through the mouth 

 into the stomach. For this it may be necessary to lift the anterior 

 end of the board. Looking back into the mouth, the puckering of 

 the gullet may be seen. Are the mouthfuls that the frog swallows 

 small or large, relatively? What is the real width of the gullet? 



5. At the posterior end of the stomach begins the intestine; 

 carefully trace it throughout its course. 



6. The widened portion of the intestine near its end is the 

 cloaca. The external opening is the anus. 



7. The thin membrane that holds the intestine in place is the 

 mesentery. To what is it attached dorsally? In a freshly killed 

 specimen blood tubes may be seen in the mesentery. The 

 mesentery is a double membrane and the blood tubes and 

 pancreas lie between the two folds. 



8. Turn the stomach and intestine forward ; the pancreas 

 should be seen in the loop formed by the intestine and stomach. 

 It has the appearance of a yellow cord, and is often hard to dis- 

 tinguish. 



9. At each side of the body cavity, usually concealed by the 

 lobes of the liver, are the two lungs. In frogs killed by chloro- 

 form the lungs are usually collapsed, that is, emptied of air; 

 hence they are small and dark-colored. If they contain air, they 

 may be very conspicuous and bright-colored. Find again the 

 glottis, or entrance of air from the floor of the mouth ; insert the 

 tip of the blowpipe and inflate the lungs. They are nearly plain, 

 hollow sacs, and not spongy all the way through like the lungs 

 of the mammals. Tie a thread tightly around the base of each 

 lung while it is inflated ; cut the lungs out and hang them up till 

 they are dry. Then cut one of them open and compare it with 

 the lung of a turtle similarly prepared. 



10. Insert the scalpel handle under the posterior end of the 

 stomach, and tip it forward with the intestine and the liver. On 



