THE FROG 41 



Make an outline drawing four inches in diameter showing 

 the relative position and proportion of these parts. Arrange 

 the drawing with the dorsal side of the cord toward the top 

 of the page. Fill in with care some of the details of structure 

 observed. 



(6) Stomach. With the low power observe the four 

 layers of the wall, as follows, from without inward: 

 (I) Serosa or Peritoneum. (This is very delicate 



and may be lacking.) 

 (II) Muscular coat, consisting of 



(1) an outer longitudinal layer. Note the 

 shape of the cells. Do all contain nuclei ? 

 How do you account for this? 



(2) an inner circular layer. What is the 

 shape of the cells? Are nuclei present? 

 What is the relative thickness of the two 

 layers? 



(III) Submucosa. Made up chiefly of connective 

 tissue and bloodvessels. Note the general 

 character of the tissue and the staining proper- 

 ties. 



(IV) Mucosa or Mucous Membrane. This is marked 

 off from the submucosa by a narrow band of 

 muscle cells (the muscularis mucosae). The sur- 

 face is covered with columnar epithelium which 

 dips down to form numerous pits into which the 

 gastric glands empty. The glands are sur- 

 rounded by connective tissue. 



Make a drawing three inches in diameter of a segment 

 of the stomach wall as seen under low power. 



Under high power study a portion of the mucosa and note 

 the following points: shape of the gastric glands; general 

 character of the epithelium lining the pits, the shape of the 

 cells and the position of the nuclei. 



