THE INTESTINES. 



93 



Fig. 207. 



(50 — 90 upon a square line) in the duodenum and jejunum, less 

 so in the ileum (40 — 70 upon a square line). In the duodenum 

 they are broader and less elevated, 

 resembling folds and laminse ^ — J"' 

 in height, J — \ or even %" in breadth. 

 In the jejunum, they appear for the 

 most part to be conical and flattened ; 

 frequently, they are even foliated or 

 cylindrical, clavate or filiform, the three 

 latter forms predominating in the jeju- 

 num. The length of the villi is from 

 I — i'"; the breadth from I — -k"\ even 



the thickness in the flattened 



Fig. 208. 



forms i '. 



The villi are composed of two por- f 

 tions, a deeper, belonging to the mucous 

 membrane and an epithelial, superficial 

 coat. The contour of the former or 

 villus proper, is similar to that of the 

 entire villus; it is simply a solid c 

 process of the mucous membrane, con- 

 taining blood-vessels, 

 lymphatics and smooth 

 muscles, whose matrix, 

 through which a varia- 

 ble number of roundish 

 nuclei are scattered, in 

 general exhibits no 

 morphological charac- 

 ter more decided than 

 that of the mucous 

 membrane itself, yet 

 must most undoubtedly be regarded as a metamorphosed 

 connective tissue, without any intermixture of elastic tissue. 

 The blood-vessels of the villi (fig. 208) are so numerous, 



Fig. 207. Intestinal villus of a young Kitten without its epithelium, to which 

 acetic acid has been added : a, boundary of the villus ; b, subjacent nuclei; c, nuclei 

 of the smooth muscles ; d, round nuclei in the centre of the villus. 



Fig. 208. Vessels of a few villi of the Mouse, after one of Gerlach's injections, 

 x 45. 



