208 GEXERAL BIOLOGY 



Compare the bones with the diagram of the vertebrate 

 skeleton as shown on page oo and then make a diagram of 

 the skeleton of this amphibian. The skeleton of fore and 

 hind feet will be easily observed if the skin be stripped off, 

 the outside muscles cut off, and the undisturbed skeletal 

 parts then cleared in dilute glycerine. The relations of 

 bone, muscles, nerves and skin will also be seen in the mak- 

 ing of the preparations. 



To the examination of the main external features of the 

 brain should be devoted the major part of the time alloted 

 to this study. Tn a shark or a large tadpole the roof and 

 the coverings of the brain are readily cut away, and -the 

 parts shown in figure 1 18 will be easily made out. 



The record of this study may consist of diagrams of 

 skeleton and brain. 



Study 28. The cellular structure of an amphibian. 



Materials needed : A living or freshly anesthetized male 

 specimen ; slide mounts of prepared fragments of the ovary 

 showing eggs and egg follicles; sections of the stomach 

 wall, the intestine, the lung, the skin, the kidney, the spinal 

 cord, etc. 



The careful study of sections is time consuming, especially 

 for a beginner, and little of it can be done in a single period. 

 To expedite their examination, a number of them may be 

 shown as microscopic projections. The student should at 

 least examine and draw a few living cells from the fresh 

 specimen, such as red and white corpuscles from the blood, 

 living sperm cells, ciliated epithelium scraped from the 

 roof of the mouth, etc. In the sections from the enteron 

 and its appendages, the types of epithelium shown in figure 

 134 should be identified, and the subjacent muscle layers, the 

 interpenetrating blood vessels and the covering peritoneal 

 layer of endothelium should be seen. In the skin section 



