844 



THE INTESTINE. 



divide, and form upon its surface, beneath the epithelium and limiting 

 membrane, a fine capillary network, from which the blood is returned for the 

 most part by a single vein. 



The lacteal lies iti the centre of the villus, and is in the smaller villi usually 

 a single vessel, with a somewhat expanded extremity, and of considerably 

 larger diameter than the capillaries of the blood-vessels around. According 

 to the observations of Teichmann, there are never more than two intercom- 

 municating lacteals in a single villus in the human subject; but both he and 

 Frey find a copious network of them in the villi of the sheep. Considerable 

 difference of opinion exists as to the nature of the wall of the lacteal in the 

 villus, and even as to whether or not any wall exists, and this point must 

 be considered as still undetermined. The epithelium of the villi is of the 

 columnar kind ; the cell-wall is delicate, and the nucleus distinct. The 

 nature of both the free and the attached extremities of the cells is involved 



Fig. 589. 



cut irregularly ; ?', the submucous layer. 



A, cross section of three tubular glands more highly magnified. 



Fig. 589. VERTICAL SECTION OF 

 THE INTESTINAL MDCOUS MEM- 

 BRANE OF THE RABBIT (slightly 

 altered from Frey). -^ 



Two villi are represented, in one 

 of which the dilated lacteal alone is 

 represented, in the other the blood- 

 vessels and lacteal are both shown 

 injected, the lacteal vhite, the 

 blood-vessels dark : the section is 

 carried through the tubular glands 

 into the submucous tissue : a, the 

 lacteal vessels of the villi ; a', below 

 the glands, the horizontal lacteal, 

 which they join ; 6, the capillary 

 blood- vessels shown only in one of 

 the villi ; c, a small artery ; d, a 

 vein ; e, the epithelium covering 

 the villi ; /, the substance of the 

 villi, piesenting interstices which 

 contain lymph-cells ; g, tubular 

 glands or crypts of Lieberkiihn, 

 some divided in the middle, others 



in some doubt. At the free extremity, they present to view a thick layer 

 of substance with vertical striee, which, on treatment with water, swells out 

 and loses its striated appearance. This layer was first recognised by Kol- 

 liker and by Funke, who both consider the striae to be minute perforating 

 canals ; while Brettauer and Steinach, and likewise Henle, maintain that 

 they are rods comparable with cilia. Briicke, previous to the discovery of 

 the striated body, advanced the opinion that the epithelium- cells were alto- 

 gether open at their free extremities, and that each communicated likewise 

 with the interior of the villus by a foramen at the deep extremity. Brettauer 

 and Steinach support Brlicke's view, in respect that they consider the striated 

 body as continuous with the cell-contents, and not with the cell-wall. With 

 regard to the deep extremities of the epithelial cells, Heidenhain believes 

 that he has observed them prolonged into fine threads, which communicate 

 with branches of anastomosing connective tissue-corpuscles, and considers 



