52 



In studying this preparation, observe that the coats recogniz- 

 able in the esophagus and stomach, also form the intestine. Deter- 

 mine the character and direction of the fibers in the two layers of the 

 muscular coat. Is a muscularis mucosa recognizable ? In the mu- 

 cosa, note the tubular crypts of lyieberkiihn extending down into the 

 mucosa, and the villi, tongue-like elevations of the mucosa. Study 

 the character of the epithelium of the intestine, noting the striated 

 border of the columnar cells and the goblet cells. Compare the epithe- 

 lium covering the villi with that of the crypts of Lieberktihn. In 

 the submucosa are the glands of Brunner with here and there a duct 

 leading through the mucosa. What relation do they have to the 

 pyloric glands ? Study carefully the structure of a villus ; (a) its 

 covering epithelium, (3) the central core of diffuse adenoid tissue, 

 (f) a strand of plain muscle ; and in comparison, study 105, 106, 

 and 6. 



105. Duodenum. Rabbit. Injected with carmine gelatin 

 mass (§ 127) ; now in clearer. Mount a piece of the mucosa, 

 villi up. 



The villi are rather short and leaf-like, flattened. Observe how 

 the arteriole passes up to near the summit of the villus, there to 

 break up into a cascade of capillaries that unite on the opposite side 

 to form one or two venules. 



106. Ileum. Rabbit. Transection. Injected with carmine 

 gelatin mass (§ 127); alcohols; collodion; now in clearer; sec- 

 tions fi. 



In the ileum the villi are longer and more filiform. Note the 

 relations of the blood vessels in the villi and compare with 105. 



107. Ileum. Rabbit. Demonstration. Blood vessels in- 

 jected with carmine gelatin mass (red) ; the central lacteal is filled 

 with Berlin blue gelatin mass (blue). Observe the position of the 

 lacteal (lymph vessel) in the villus, its extent and size in compari- 

 son with the blood capillaries. By means of 6, 104, 106 and 

 107 a fairly complete idea may be formed of the structure of a villus ; 

 from your physiology recall the part played by the epithelium in 

 absorption and what food stufiFs pass into the lacteal and what are 

 taken up by the blood vessels. 



108. Fat absorption. Intestine of the frog. Flemming's 

 fluid (§ 24) ; paraffin. The frog was fed with bacon 24 hours be- 



