DIGESTION. 263 



cells presenting an appearance precisely similar to the " striated basilar 

 border " which covers the villi. 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. 



Among the columnar cells of Lieberkiihn's follicles, goblet cells fre- 

 quently occur (Fig. 193). 



(2.) Brunner's glands (Fig. 196) are confined to the duodenum; they 

 are most abundant and thickly set at the commencement of this portion 

 of the intestine, diminishing gradually as the duodenum advances. They 

 are situated beneath the mucous membrane, and imbedded in the sub- 

 mucous tissue, each gland is a branched and convoluted tube, lined with 

 columnar epithelium. As before said, in structure they are very similar 

 to the pyloric glands of the stomach, and their epithelium undergoes a 

 similar change during secretion; but they are more branched and con- 

 voluted and their ducts are longer. (Watney.) The duct of each gland 

 passes through the muscularis mucosae, and opens on the surface of the 

 mucous membrane. 



(3. ) The glands of Peyer occur chiefly but not exclusively in the small 

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

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

 tions, viz., either scattered singly, in which case they are termed glan- 

 dulce 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 glandules agminatcv, the groups being commonly called Peyer's 

 patches (Fig. 197), and almost always placed opposite the attachment of 

 the mesentery. In structure, and in function, there is no essential dif- 

 ference between the solitary glands and the individual bodies of which 

 each group or patch is made up. They are really single or aggregated 

 masses of adenoid tissue forming lymph-follicles. In the condition in 

 which they have been most commonly examined, each gland appears as 

 a circular opaque-white rounded body, from -fa to -fa inch in diameter, 

 according to the degree in which it is developed. They are principally 

 contained in the submucous coat, but sometimes project through the 

 muscularis mucosce into the mucous membrane. In the agminate glands, 

 each follicle reaches the free surface of the intestine, and is covered with 

 columnar epithelium. Each gland is surrounded by the openings of 

 Lieberkiihn's follicles. 



The adjacent glands of a Peyer's patch are connected together by 

 adenoid tissue. Sometimes the lymphoid tissue reaches the free surface, 

 replacing the epithelium, as is also the case with some of the lymphoid 

 follicles of the tonsil (p. 242). 



Peyer's glands are surrounded by lymphatic sinuses which do not 

 penetrate into their interior ; the interior is, however, traversed by a 



