PEYERS GLANDS. 



241 



FIG 74. 



mucous membrane, thickly distributed over the whole surface 

 both of the large and small intestines. In the 

 small intestine they are visible only with the 

 aid of a lens ; and their orifices appear as mi- 

 nute dots scattered between the villi. They 

 are larger in the large intestine, and increase 

 in size the nearer they approach the anal end 

 of the intestinal tube ; and in the rectum their 

 orifices may be visible to the naked eye. In 

 length they vary from ^ to ^ of a line. Each 

 tubule (Fig. 74) is constructed of the same es- 

 sential parts as the intestinal mucous mem- 

 brane, viz., a fine structureless membrana pro- 

 pria, or basement-membrane, a layer of cylin- 

 drical epithelium lining it, and capillary blood- 

 vessels covering its exterior. Their contents 

 appear to vary, even in health ; the varieties 

 being dependent, probably, on the period of 

 time in relation to digestion at which they are 

 examined. At the bottom of the follicle, the 

 contents usually consist of a granular material, in which a 

 few cytoblasts or nuclei are imbedded; these cytoblasts, as 

 they ascend towards the surface, are supposed to be gradually 

 developed into nucleated cells, some of which are discharged 

 into the intestinal cavity. The purpose served by the material 

 secreted by these glands is still doubtful. Their large number 

 and the extent of surface occupied by them, seem, however, 

 to indicate that they are concerned in other and higher offices 

 than the mere production of fluid to moisten the surface of the 

 mucous membrane, although, doubtless, this is one of their 

 functions. 



The glands of Peyer occur exclusively in the small intestine. 

 They are found in greatest abundance in the lower part of the 

 ileum near to the ileo-csecal valve. They are met with in two 

 conditions, viz., either scattered singly, in which case they are 

 termed glandulce solitaries, or aggregated in groups varying 

 from one to three inches in length and about half an inch in 

 width, chiefly of an oval form, their long axis parallel with 

 that of the intestine. In this state they are named glandulce 

 agininatce, the groups being commonly called Peyer's patches 

 (Fig. 75). The latter are placed almost always opposite the 

 attachment of the mesentery. In structure, and probably in 

 function, there is no essential difference between the solitary 

 glands and the individual bodies of which each group or patch 

 is made up; but the surface of the solitary glands (Fig. 76) is 

 beset with villi, from which those forming the agminate 



