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 Lieberkiihn 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 Lieberkiihn. 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, () the central core of diffuse adenoid tissue, 

 (r) 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. 



1 06. Ileum. Rabbit. Transection. Injected with carmine 

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

 tions \vr\> yu. 



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 stuffs pass into the lacteal and what are 

 taken up by the blood vessels. 



1 08. Fat absorption. Intestine of the frog. Flemming's 

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



