THE FROG 



VI. ANIMAL CELLS; MITOSIS. 



1. Epithelial Cells. Obtain a small piece of the outer 

 layer that has been shed from the skin of a frog; mount it in 

 a drop of water on a slide and cover it with a cover glass. 

 With the microscope observe the small polygonal areas 

 bounded by the cell walls. Within each of these areas ob- 

 serve a central granular body, the nucleus; between the 

 nucleus and the cell wall is the finely granular cytoplasm. 

 Both nucleus and cytoplasm are forms of protoplasm. 

 Under the high power of the microscope, draw, five or six 

 contiguous cells, making the outline of each cell about fifteen 

 millimeters in diameter. 



With a clean scalpel gently scrape the inside of your 

 cheek, mount the scraping in a drop of water on a slide, 

 cover it with a cover glass and examine with the microscope. 

 Under high power draw three or four cells. 



The above tissues are representative of flattened or 

 squamous epithelium. As an example of columnar epi- 

 thelium, study and sketch a portion of a cross-section of the 

 integument of Amphioxus, using the high power of the 

 microscope. 



2. Red Blood Corpuscles. Examine a stained prepara- 

 tion of the red blood corpuscles of the frog. Under high 

 power, sketch a few of these cells as seen from the broad 

 side; if possible find and draw an edge view. Is a cor- 

 puscle thicker at its margin or at its center ? Each drawing 

 should measure about two centimeters in its longer diameter. 



3. Cartilage. Obtain a thin slice of cartilage cut from 

 the head of the femur of a frog, mount it in water on a 

 slide and cover it with a cover glass. With the low power of 

 the microscope locate a clear portion of the cartilage and 



