38 GENERAL BIOLOGY 



section of the body of the frog showing all the organs and 

 parts in their proper relation and proportion. 



VH. Microscopic Anatomy. (Histology.) 



This involves the study of the tissues and cells of which 

 the various organs are composed. It will be found that 

 there are only a few kinds of fundamental tissues and these 

 are repeated over and over again in the various organs. The 

 relations of shape and position may differ somewhat in 

 different places, but the tissues have the same general ap- 

 pearance and function wherever they are found. 



1. Tissues. 



(a) Blood. Mount a drop of the blood of a frog on a slide, 

 and cover with a cover glass. Observe the colorless 

 fluid or plasma in which are floating the corpuscles 

 or blood cells. How many kinds of cells do you find? 

 Observe their shape, color, relative size, and compar- 

 ative numbers. Are the cells nucleated? If the slide 

 is placed on a warm stage it may be possible to 

 demonstrate the movement of the white corpuscles. 

 Draw. 



(b) Epithelium. Epithelial tissues are those which cover' 

 the free surfaces of the body or line cavities. The 

 outer skin and the lining of the digestive tube are 

 examples. Epithelium is of different kinds according 

 to the shape, structure and arrangement of the cells. 

 (I) Squamous or Scaly. Examine the epidermis of 



the frog. What is the form of the cells? Are 

 nuclei present? Do the cells form a layer? Do 

 they overlap at the edges? If possible examine 

 sections made vertically through the entire skin. 

 In these sections only the outer layers of cells 

 make up the epithelium. Draw. 



