THE FROG 39 



(II) Columnar. Examine prepared slides which show 

 sections through the intestine of the frog. What 

 is the form of the cells lining the cavity? How 

 are they placed? What is the position of the 

 nuclei in the cells? Goblet cells, which contain 

 secretions of mucus, are often found in the 

 epithelium. Draw. 



(Ill) Ciliated. Examine the cells scraped from the 

 roof of the mouth of a freshly killed frog. Com- 

 pare the cells with those of squamous and colum- 

 nar epithelium in all points. In what are they 

 alike? In what different? Can you see the 

 movement of the cilia? Where on the cells are 

 the cilia located? Draw. 



(c) Cartilage. Examine prepared slides of cartilage, or 

 make a slide of fresh cartilage from the frog. Get a 

 very thin piece and observe the transparent matrix 

 in which are embedded the cartilage cells. Note 

 the shape and the size of the cells and the manner in 

 which they are grouped together. How does the 

 cartilage differ in appearance from the other tissues? 

 Are the cells nucleated ? Do you find cells with more 

 than one nucleus? Explain. To what does the 

 matrix correspond in the other tissues? Draw. 



(d) Muscle. 



(I) Striated. The striated (voluntary) muscles are 

 those that are under the control of the will. 

 Examine the muscle of the leg of the frog, by 

 teasing it in salt solution. The fibers should be 

 well pulled apart. What is the shape of the 

 fibers? Do they tend to separate into smaller 

 fibrillae? Is there anything that suggests the 

 name "striated" muscle? If nuclei are present 

 where in the fiber are they located? Draw. 



