OTHER ORGANS OF DIGESTION. 65 



6. The mucous coat. 



1. How thick is this coat? 



2. Do you find the shallow pits on the surface? 



3. The long tubes opening on the inner surface are 



the gastric glands. 



c. The submucous coat lies between the mucous and 

 the muscular coats. What do you find here? 



d. Sketch. 



II. THE MICROSCOPICAL STRUCTURE OF THE WALL 

 OF THE SMALL INTESTINE. 



Examine with the compound microscope a cross-section 

 of the wall of the small intestine that has been injected. 



Notice : 



a. The muscular coat. 



1. How thick is it? 



2. Which way do the fibres extend? 



b. The mucous coat. 



1. Is it as thick as that of the stomach ? 



2. Do you find the villi ? Notice the blood-vessels 



in them. The lacteal is the large vessel in 

 the centre of each villus. 



3. The tubular glands opening on the inner surface 



are the crypts of Lieberkuhn. 



c. The submucous coat is just beneath the mucous coat. 

 What does this contain ? 



d. Sketch. 



