THE SMALL INTESTINE. 



1641 



The walls of the latter, however, are so closely applied to the nodules that the exist- 

 ence of the pit is not at first evident. Villi are wanting over the prominence of the 

 nodules ; likewise the glands of Lieberkiihn, the orifices of which are arranged as a 



wreath around the nodules. The 



IG. 1394- latter are found as much on one 



side of the intestinal tube as on 

 the other. 



In structure the solitary nod- 

 ules correspond to similar lymph- 

 nodes in other localities, con- 

 sisting of a capsule of denser 

 tissue enclosing the delicate ade- 

 noid reticulum which supports 

 the characteristic lymphocytes 

 within its meshes. Within the 

 larger nodules germ-centres, 

 spherical or ellipsoidal in form, 

 occupy the middle of the nodules; 

 the germ-centres are, however, 

 not constant, being present, as a 

 rule, in young subjects, but often 

 absent in old individuals. A 



Peyer's 

 patch 



Solitary, 

 nodule 



Surface view of portion of mucous membrane of ileum, showing 

 Peyer's patch and solitary lymph-nodules. Natural size. 



generous blood-supply is pro- 

 vided by the rich net-work of 

 small vessels which surrounds the nodules ; fine capillaries penetrate into their interior, 

 but usually do not reach the centre of the nodes. Definite lymph-paths have not 

 been demonstrated within the nodules, although a plexus of lymphatics surrounds 

 their exterior (Teichmann). 



Peyer's patches (noduli lymphatic! aggregati) are collections of solitary 

 lymph-nodules, the individual follicles being blended by intervening adenoid tissue. 

 They are seen in the lower half of the small intestine, especially near the lower end 

 (iieum) ; exceptionally they are found in the upper part of the jejunum in the 

 vicinity of the duodenum. The patches appear as slightly raised, elongated ovals, 



FIG. 1395. 



Submucous fold supporting mucosa with villi 



Transverse section of ileum, showing Peyer's patch cut across. X 10. 



always on the side of the intestine opposite to the attachment of the mesentery. 

 Their usual number is about thirty, although as few as eighteen and as many as 

 eighty-one have been counted (Sappey). In length they ordinarily measure from 



