294 



THE DIGESTIVE SYSTEM 



some cells are of a basophile nature (Klein*). In others they 

 contain still coarser granules which are strongly eosinophile. The 

 exact function of these peculiar cells is unknown, but that they 

 are true secreting cells seems highly probable. 



The crypts of Lieberkiihn are confined to the narrow deeper 

 zone of the intestinal mucous membrane. Their lumen, after 

 fixation, contains only the coarsely reticular mucous secretion. 



The student should be warned to distinguish carefully between 

 the transverse sections of the tubular crypts which are confined 

 to the deep zone of the mucous membrane and the similar sections 



of the villi which are only found in 

 the superficial zone and whose epithe- 

 lial coat, instead of inclosing a mere 

 reticular mass of mucous secretion 

 invests an organized body of diffuse 

 lymphoid tissue. 



THE GLANDS OF BRITNNER 

 are tubulo-acinar glands which fur- 

 nish a muco-albuminous secretion. 

 They appear to represent the contin- 

 uation into the intestine of the py- 

 loric glands of the stomach, and 

 they occur in decreasing proportion 

 throughout the entire length of 

 the duodenum. They are, however, 

 sharply distinguished from the py- 

 loric glands by their large size, the 

 secreting portions of Brunner's glands 

 being only found in the submucosa 

 and the deeper part of the mucous 

 membrane, where their secreting acini 

 form innumerable groups, the tubules 

 of each of which are connected with 

 the terminal subdivision of a duct. 



The ducts of Brunner's glands 

 open on the free surface between the 

 villi by means of crypt-like tubules 

 which are lined by tall columnar epithelium and can only with 

 difficulty be distinguished from the adjacent crypts of Lieber- 

 kiihn. In the deeper part of the mucous membrane the ducts 



* Am. Jour. Anat., 1902, Proc. Am. Assoc. Anat. 



FIG. 240. RECONSTRUCTION MODEL 

 OF A BRUNNER'S GLAND, FROM 

 THE HUMAN DUODENUM. 

 Three partially blended ducts 



pass into the submucosa and end in 



expanded alveoli, x 344. (After 



Maziarski.) 



