474 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



vessels, with a magnificent network of peripheral capillary blood-vessels ; the 

 whole being enclosed in a complete epithelial sheath. 



Fig. 275. 



A. VILLI OF MAN, SHOWING THE BLOOD-VESSELS AND LACTEALS. B. VILLUS OP A SHEEP. 



Fig. 276. 



The orifices opening on the intestinal mucous membrane belong either to 

 Brunner's {duodenal) glands, or to those of Leiberkiihn {simple follicles). 



Brunner's glands form a continuous layer 

 beneath the duodenal mucous membrane. 

 They are tubular glands, ramifying and 

 flexuous, which open on the surface of the 

 mucous membrane, either by a special ex- 

 cretory canal, or through the medium of a 

 Lieberkiihn's gland. (These glands secrete 

 a clear alkahne mucus, which contains no 

 formed elements, such as cells or nuclei.) 



The glands {cryptm mucosa) of Lieher- 

 'kiilin or Gnleati are placed in the substance 

 of the mucous membrane, and are distin- 

 guished by their microscopical dimensions, 

 their considerable number, and their tubular 

 form, which has caused each of them to be 

 compared to the finger of a glove ; they 

 are implanted perpendicularly in the mem- 

 brane, and open on its free surface. They are found throughout the whole extent 

 of the intestine, and are lined with spheroidal epithelium. 



The solitary glands or follicles {glandulce solitarice, or lenticular glands) are 



PORTION OF ONE OF BRUNNER's GLANDS. 



