EPITHELIUM OF THE VILLI. 845 



that, by means of deep branches of these anastomosing cells opening into the 

 cavity of the lacteal, a channel of communication is established between the 

 lacteal and the surface of the villus. This view has met with some accept- 

 ance from its seeming to offer an explanation of the mode in which particles 

 of oil are conveyed from the intestines into the lacteals ; but it cannot 



Fig. 590. 



QjO2n* e m 



W n 



Fig. 590. EPITHELIUM OF THE INTESTINAL VILLUS OF A RABBIT (from Kolliker). 



A, ^ ; B, aft 



A, series of the cylindrical epithelial cells separated from a villus ; a limiting or cuti- 

 cular membrane or border is seen passing over the free ends of the cells. 



B, some of the same cells treated with water ; in 1 and 2, and at a, in the left hand 

 series of cells, the striated or porous border is seen ; and at b, in the latter, pellucid drops 

 of mucus which have escaped from the cells. 



at present be considered as satisfactorily established. The muscular tissue 

 within the villi was first discovered by Briicke : it consists of a thin stratum 

 of smooth fibres disposed longitudinally round the commencement of the 

 lacteals. Although not always discernible in man, these fibres are distinct 

 in animals ; and in them, on being stimulated, they produce, according to 

 Briicke, a very obvious retraction of the villi. 



During digestion, the epithelial cells become turbid with minute oil drops 

 in their interior, which obscure their nuclei. The tissue of the villus itself 

 becomes turbid in like manner ; and clear globules may also be observed, 

 both in the epithelial cells and deeper tissue, which, however, there seems 

 reason to believe, are formed by the running together of smaller particles 

 after death. Kolliker and Donders have both observed minute particles of 

 oil in their passage through the striated body. 



A full bibliography, on the subject of the villi, is given by Teichmann in his work 

 "das Saugadersystem," (1861), pp. 77 et seq. ; and the questions at issue are fully 

 discussed in Kb'lliker's Gewebelehre, 4th edition, and Henle's System. Anatomic. See 

 also Frey, in Zeitsch. f. Wissensch. Zoologie, vol. xiii. Heidenhain's paper is in Mole- 

 schott s Untersuchungen z. Naturlehre, vol. iv. Peculiar epithelial cells with deeply 

 hollowed cup-shaped extremities, have been pointed out by Henle, interspersed 

 among the others. It is yet uncertain whether they are a distinct kind of cell, or 

 only a peculiar condition of the ordinary sort. 



3. Glands. The glandular structures found in the mucous coat of the 

 small intestine are the crypts or follicles of Lieberkiihn, the solitary gland?, 

 the patches of Peyer's glands, and Brunner's glands, the last being peculiar 

 to the duodenum. 



The crypts of Lieberkiihn, the smallest of these glandular structures, are 

 found in every part of the small intestine, between the villi, and surrounding 

 the larger glands. They consist of minute tubes, closed at their attached 

 extremity, and placed more or less perpendicularly to the surface, upon 



