404 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



dicularly in the mucous membrane, and open on its free surface. They 

 are found throughout the whole extent of the intestine, and are lined with 

 columnar epithelium. 



The solitary glands (glandulce solitaries, or lenticular glands) are round, 

 salient bodies, visible to the naked eye. They are somewhat rare in the 

 small intestine, but are more abundant at the posterior portion of the large 

 intestine. They are formed by a mass of lymphoid elements enveloped by 

 some condensed fasciculi of connective tissue. Above them the mucous 

 membrane is slightly umbilicated, and is destitute of villi and tubular glands, 

 though these are arranged in a circle around the follicles, to form the 

 coronce tubulorum. (The solitary glands usually contain a cream-like 

 secretion, which covers the villi on their free surface.) 



Fig. 199 



PERPENDICULAR SECTION THROUGH ONE OF PEYER's PATCHES IN THE LOV r ER PART 

 OF THE ILEUM OF THE SHEEP 



a, a, Lacteal vessels in the villi : 6. b. Superficial layer of the lacteal vessels (rete 

 angustum); c, c, Deep layer of the lacteals (rete amplum)', d, d, Efferent vessels 

 provided with valves ; <?, Lieberkiihn's glands ; /, Peyer's glands ; g, Circular 

 muscular layer of the wall of intestine ; h, Longitudinal layer ; , Peritoneal layer. 



The aggregated follicles (glandulae agminatse) are nothing more than 

 solitary glands collected together in a limited space, where they constitute 

 what are known as the glands of Peyer or of Pecklin, or the honeycomb 

 glands. Absent in the duodenum, and even at the commencement of the 

 jejunum, these glands, about a hundred in number, are very irregularly 

 placed on the internal surface of the intestine at its great curvature, on the 

 side opposite to the mesentery. Their form is oval or circular, and the 



