2/6 



THE DIGESTIVE ORGANS. 



of cells found in the lumen of the intestine proportionate to the leuco- 

 cytes present in the epithelium. Since many are seen in the epithe- 

 lium undergoing karyokinetic division, it is more probable that a 

 part of them actually wander into the epithelium for the purpose of 

 division (chemotaxis ?), only to return to the mucosa after the com- 

 pletion of the process (compare p. 61). 



Into the spaces between the villi open numerous tubular glands. 

 These are seldom branched, and are known as Lieb crkilJ in' s glands t 

 or crypts. Their length varies from 320 fj. to 450 //. They are 

 regularly arranged in a continuous row, and often have an ampulla- 

 like widening of their lumina extending almost to the muscularis 

 mucosae, but never quite reaching it. They are uniformly distrib- 

 uted not only throughout the small intestine, but also throughout 

 the large intestine and rectum. The cells lining the crypts of the 



small intestine are about 

 one-half as long as those 

 covering the villi ; a cuticu- 

 lar border is seen on the 

 cells lining the upper part 

 of the glands, but is ab- 

 sent in the cells lining the 

 fundus of the glands. The 

 cells are conical in shape, 

 a condition probably due 

 to the curvature of the 

 glandular wall, the base 

 of each cone lying toward 

 the basement membrane, 

 the apex toward the lumen 

 of the gland a condition 

 opposite to that found in 

 the villi. Numerous goblet 

 cells are also present. They 

 vary only slightly in shape 

 during mucous secretion, 

 and do not, as in the villi, 

 assume the form of goblets 

 with distinct pedicles. Mito- 

 ses are always seen in the 

 intestinal glands, especially 

 in cells which do not con- 

 tain mucin. They are 

 readily distinguished, since 



the nuclei in process of division, as we have seen, lie .outside of the 

 row formed by the remaining nuclei. The plane of division in 

 these cells lies horizontal to the long axis of the gland, so that an 

 increase in the number of cells results in an increase in the area of 

 the glandular walls. Mitoses are very rarely observed in the epi- 



Fig. 217. Longitudinal section through sum- 

 mit of villus from human small intestine ; X 9 

 (Flemming's solution) : At a is the tissue of the 

 villus axis ; /;, epithelial cells ; c, goblet cell ; d, 

 cuticular zone. 



