130 THE ALIMENTARY SYSTEM. 



(millimetre long, which thickly stud the inner surface of the 

 /entire small intestine. In places they exhibit slight constric- 

 tions, called Watney's nodes. They are covered with a single 

 flayer of long columnar epithelial cells (Fig. 13), with their 

 f nuclei near their attached bases. The protoplasm of the free 

 ends of these cells contains fine parallel longitudinal striae, 

 giving the appearance of a narrow striated border. Goblet- 

 cells are numerous among the columnar cells. 



The epithelium-cells rest on a basement-membrane, and the 

 framework in the interior of the villi is made up by an open 

 connective-tissue reticulum, the meshes of which contain free 

 lymphoid cells, forming a diffuse lymphoid tissue. The core 

 or axis of the villas is formed by a small lacteal, a lymphatic 

 capillary or radicle ; this is a tube or sac formed by a single 

 layer of endothelium-cells, with a blunt or slightly expanded 

 blind extremity above (toward the lumen of the intestine), and 

 emptying below into the larger lymphatic vessels of the sub- 

 mucosa. A minute artery enters each villus and breaks up 

 into a rich capillary network which surrounds the lacteal. 

 Muscular projections from the muscularis mucosae extend up 

 into the villi, and apparently serve by periodical contraction 

 to empty them of their contents. The Junction of the villi is 

 to absorb the digested food-materials from the intestinal ogcnal 

 into the blood and lymph circulations. They especially 

 absorb the insoluble and indiffusible fatty matters, which pass 

 through the epithelium-cells in small granules, through the 

 reticulum of the villus, and make their way into the lacteal. 



The intestinal glands, or Jollities of Lieberkahn, are straight 

 simple tubular glands between the bases of thePvilli, ard dip 

 down to the muscularis mucosse. They, and the surface between 

 their orifices, are lined with a single layer of short granular 

 columnar epithelial cells, with nuclei near their bases, which 

 rest on a basement-membrane. Goblet-cells are interspersed 

 among these columnar cells. These glands occur throughout 

 the small and large intestines ; they secrete the intestinal juice 

 and also perhaps have absorptive functions. 



The subepithelial connective tissue of the mucosa, the ana- 

 logue of the tunica propria, consists of a delicate reticular 

 tissue, embracing the glands and projecting up to form the 

 framework of the villi, the surface condensed into a basement- 





