76 STUDIES OF ANIMAL TYPES 



Make a diagrammatic drawing of the heart and its 

 arteries. 



Digestive organs. Push a long probe through the pharynx 

 and gullet into the stomach. What is the shape of the stom- 

 ach? How large is it? 



The intestine begins at the posterior end of the stomach. 

 Trace its turns and windings to the enlarged posterior por- 

 tion, the cloaca. How is the intestine held in place ? From 

 what is it suspended ? The thin tissue supporting the in- 

 testine is called the mesentery. 



The liver has been already described. 



The pancreas is a whitish, compact organ lying between 

 the stomach and intestine. 



Make a diagram of the alimentary canal. 



Respiratory organs. Find the glottis and inflate the 

 lungs. They are usually concealed by the liver. How 

 many lobes to the lungs ? What color are they ? Dissect 

 out the windpipe and trace it to the mouth. 



Excretory organs. There are two reddish brown kidneys 

 on the dorsal side of the body cavity near the cloaca. In 

 the extreme posterior end of the body cavity will be found 

 the urinary bladder. It is a thin sac and is usually empty. 



D. DEVELOPMENT AND LIFE HISTORY. The eggs of the 

 frog are laid in large, irregular, jelly like masses in spring, 

 in the shallower parts of ponds and streams near the shore. 

 They may be gathered and brought to the laboratory in 

 water. Place some of them in a large tin milk pan. Tilt 

 the pan by placing something under one edge, and put in 

 enough water to cover the bottom an inch deep in the shal- 

 lower part. It would be well to siphon this water out 

 occasionally and put in some fresh. Gather some mud, 

 pond scum, rocks, and leaves with fine slimy sediment on 



