THE DIGESTIVE APPARATUS. 



H7 



That the whole intestinal canal is lined with cylindrical epi- 

 thelium, was mentioned in the second lecture. We also de- 

 scribed the peculiarity which the cylinder cells of the small 

 intestines presented, the thickened seam, permeated by 

 porous canals, of the free broad surface. 



We now turn to the glands. By far the more important 

 formations are the Lieberkuhnian tubular glands (Fig. 137, a). 

 They are infinitely numerous, and occupy not only the mu- 

 cous membrane of the small, but also that of the large intes- 

 tine. We are thus reminded of the gastric glands ; the 

 capillary net-work is also the same. 



The Lieberkuhnian glands are smaller, however ; they are 

 only 0.38 to 0.45 mm. long, and 0.056 to 0.09 mm. broad. 

 Their membrana propria also appears more delicate ; the 

 tube remains undivided, and is lined by a simple layer of cyl- 

 indrical gland cells (Fig. 117, b). The opening occurs regu- 

 larly in the narrow vales which are enclosed by the adjacent 

 villi. They secrete the intestinal juice. 



The racemose or Brunonian glands (Fig. 138) of the small 

 intestine are of far more subordinate importance. They com- 



Fig. 138. — A human Brunner's gland. 



mence, in man, just beyond the stomach, and form, in a 

 crowded sequence, a regular glandular cushion embedded in 

 the submucous tissue. They thus extend to about the en- 



