166 INTESTINAL MUCOUS MEMBKANE. 



to Tsad of a line in diameter) ending by a blind and 

 somewhat bulbous extremity; this is the origin of a 

 lacteal vessel (PL XXVII. fig. VI. 2). The situation 

 of this solitary vessel in the centre of the villus, 

 compared with the position, on its surface, of the 

 capillary plexus, so rich in blood-vessels, should teach 

 us that the activity of its function as an absorbent is 

 subordinate to that of the elements by which it is 

 surrounded. The remainder of the villus consists of 

 a material faintly fibrillated rather than amorphous, 

 which encloses a number of oval nuclei, the meaning 

 of which is unknown (PL XXVI. fig. VII. 3). 

 Around the outer surface of the lacteal, non-striated 

 fibres of muscular tissue are sometimes found, running 

 parallel with the axis of the villus. We know nothing 

 of the connexion of the nervous system with the villi. 

 The glandular apparatus of the small intestine is 

 composed of clusters of follicles, tubular glands, and 

 ductless follicles. 



Glands of Brun- Brunue^ s glands are clusters of follicles, situated 

 deeply in the mucous membrane, or rather in the sub- 

 mucous layer of connecting tissue. They are little 

 yellowish-white granules, averaging one-half a line in 

 diameter, and precisely similar in structure to the 

 salivary glands ; they are provided with a single 

 layer of polygonal epithelium, and they secrete an 

 alkaline fluid in which no organic element is disco- 

 verable (PL XXVI. fig. IX.). These glands are only 

 found in the duodenum. 



Glands of Lieber- ^he tubular glands, or follicles of Lielerlvuhn, 

 placed side by side like quills in a bundle, constitute 

 a secretory apparatus which occupies the whole 



