THE INTESTINES. 



475 



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 in some 

 condensed fasciculi of connective tissue. Around them the mucous membrane is 

 slightly umbilicated, and is destitute of villa 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-Uke secretion, which covers the villi on 

 their free surface.) 



The aggregated follicles (glandulce agminatce) are nothing more than solitary 

 glands collected together in a limited space, where they constitute what are 



Fig. 277. 



PERPENDICULAR SECTION THROUGH ONE OF PEYER'S PATCHES IN THE LOWER PART OF THE 

 ILEUM OF THE SHEEP. 



a, a, Lacteal vessels in the villi ; h, b, superficial layer of the lacteal vessels (rete angustum) ; c, e, 

 deep layer of the lacteals {rete amplum); d, d, efferent vessels provided with valves; e, Lieber- 

 kiihn's glands ; /, Peyer's glands ; g, circular muscular layer of the wall of intestine ; h, longi- 

 tudinal layer ; i, peritoneal layer. 



known as the glands of Pei/er or of PecMin, Peyer's patches, or the honeycomb 

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

 these glands are about a hundred in number, and 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 smallest scarcely measure 

 more than some few hundredths of an inch square, while the diameter of the 

 largest increases to 1| inch. 



(Each of these patches is composed of a group of small, round, whitish 

 vesicles, covered with mucous membrane ; these vesicles consist of a moderately 

 thick external capsule, having no excretory canal, and containing a similar 

 secretion to that in the solitary follicles. They are surrounded by a zone or 

 band of simple follicles, and the spaces between them are covered with villi. 



