^4 



TEE 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 OF 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 foil ides). 



Brunner's glands form a continuous layer 

 beneath the duodenal mucous membrane. 

 They are tubular glands, ramifying and 

 fiexuous, 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 alkaline mucus, which contains no 

 formed elements, such as cells or nuclei.) 



The glands {cryptce mucosa') of Lieher- 

 kiihn or Galeati 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 epitheUum. 



The solitary glands or follicles (glandulm solitarice, or lenticular glands) are 



PORTION OF ONE OF BRUNNER S GLANDS. 



