278 ELEMENTARY ZOOLOGY. 



external structure. Compare as many species of frogs 

 and toads as you can get with the species you are study- 

 ing in these matters of general form and color. 



C. Internal Anatomy. The skin and its attachment to the body. 



A study of the chief muscles revealed by removing the skin; 

 especially those of the hind leg and of the ventral surface of the body. 

 Make a diagram of their position, form, and attachments. 



The organs as they lie when revealed by cutting the muscular 

 wall covering the abdomen. Identify all, and draw in place. 



Press the dark colored liver aside and find the relation and com- 

 parative length and size of the following: esophagus, stomach, 

 intestine, rectum. How is the intestine held to the body wall? 

 Open the digestive tract from end to end and compare the regions. 



Remove the digestive tract and find the kidneys, the fat bodies, 

 and the reproductive bodies in the dorsal part of the body cavity. 

 How do you identify these? Are there any outlets for the kidney 

 or the ovaries and testes ? What is the sex of your specimen ? How 

 do you know? 



Look well front for the lungs. How many? How attached? 

 Do they communicate with the mouth? Cut them open and ex- 

 amine the inner surface. 



The heart; what is its position in relation to the other organs? 

 What is its shape? its attachments? Cut into it carefully and see 

 how many chambers it has. Can you find any large vessels leaving 

 the heart? From what portions? Determine, by reference to the 

 books, what these are. 



The course of the circulation can be studied only by injecting a 

 colored mass into the aorta while the tissues are soft, after chloroform- 

 ing. After this treatment the principal vessels may be dissected. 

 A large frog should be used for this purpose. 



Find the white, glistening nerves, after removing the organs from 

 the body cavity. How many are there? Where do they arise? 

 To what regions do they run? 



The skeleton may be studied by picking and scraping away the 

 muscles and connective tissue. A little boiling will make this more 

 easy. 



The student should identify the following regions and study the 

 bones that enter into each: 



The axial skeleton, made up of the head, and the vertebrae, 

 and the breast bone; the appendicular skeleton, made up of the 

 legs and the bones to which they are attached (girdles) . The follow- 



