458 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



ready explanation. Each villus under the epithelial coat is supplied 

 with a layer of pale muscular fibres, and when these contract, the central 

 chyle- vessel being full, the effect must be to press out the contents of 

 the central vessel in the direction of the thoracic duct, at the same time 

 emptying the capillary vessels by pressure. When, now, the muscular 

 fibres relax, the capillaries will again become filled, and by the turgidity 

 of the net-work of blood-vessels cause the central vessel to become 

 expanded, and so exert a certain amount of suction in the interior of 

 the villas since the valves in the lymphatics will prevent regurgitation 



FIG. 170. SECTION OF AN INTESTINAL VILLUS OF A HORSE. (Ellcnbergcr.) 



A, epithelium ; B, adenoid tissue ; C, commencement of lacteal. 



from the mesenteric vessels. Each villns may therefore be regarded as a 

 minute lymphatic heart, which fills itself from the interior of the villus 

 in dilating, and in contracting forces its contents into the circulation. 



In addition to the absorption of fat, it is evident that other sub- 

 stances contained in the intestinal contents will also mechanically be 

 drawn into the villus with the oil-globules. Thus, unchanged albumen 

 ma}^ be absorbed in this manner and has been found in the contents of 

 the chyle-vessels. 



