ABSORPTION 



273 



adenoid tissue (p. 266) ; this tissue is relatively larger in amount 

 in the villi of carnivora than of herbivora (Fig. 85). Covering 

 the adenoid tisue is a basement membrane on which is set a layer 

 of columnar cells, placed so that their narrowest end is next the 

 basement membrane, and their broadest at the surface of the 

 villus. The cells at their narrowest part are in touch with 

 the adenoid tissue of the villus. Each cell contains a nucleus, 

 and on that edge next the interior of the bowel is a clear band 

 bearing fine striations. Lying between the columnar cells are 

 others which from their shape are spoken of as ' goblet cells ' 

 (Fig. 86) ; by means of a pore they extrude their contents, con- 

 sisting of a transparent material known as mucin, into the 

 intestine. Within the villus are bands of involuntary muscle 

 fibre arranged parallel to the axis of the villus, by the contraction 

 of which, combined with the peristaltic movements of the intes- 



Epithelium. 



dog. rabbit. 



Fig. 86. — Transverse Section of Villi of Carnivorous and Herbivorous 

 Animals (Waller, after Heidenhain). 



The large cells in the epithelial zone of the dog are the goblet cells. 



tine, the capacity of the lacteal vessel is altered in such a way 

 that it is alternately filled with lymph from the reticular adenoid 

 tissue, and emptied of lymph into the lymphatic vessel at the 

 base of the villus. This is known as the pumping action of the 

 villus, and provides an important factor in the furtherance of 

 the chyle (lymph) towards the thoracic duct. 



The other lymph radicles found in the intestine are the Solitary 

 Follicles, which are found studding the whole of the mucous 

 membrane of the small intestines ; these solitary follicles are, at 

 certain places in the ileum, collected into masses, where they are 

 known as Peyer's Patches. 



The Solitary Follicle is essentially a lymphatic structure, and is 

 not concerned like the villus in absorbing anything from the 



