THE INTESTINES. 



519 



posed over the whole mucous membrane ; and 2, racemose glands, in 

 the submucous tissue of the duodenum. 



The racemose glands, or as they are more commonly named, after 

 their discoverer, Brunner's glands, form, at the commencement of the 

 duodenum, upon the outer side of the mucous membrane, a continuous 

 layer, which is best developed and thickest, close to the pylorus, where 

 it constitutes a considerable glandular ring and extends -about as far as 

 the aperture of the biliary ducts. If the two layers of the muscular 

 tissue be dissected off a stretched or distended duodenum, the glands 

 may readily be recognized as yellowish, flattened bodies of To-lJ ^ nes 

 (on the average -J a line,) with their angles rounded off, which, en- 

 closed within a little connective tissue, lie close to the mucous membrane 

 and send short excretory ducts into it. In their minute structure, 

 Brunner's glands, the terminal vesicles of which measure 0-03-0-06, 

 even 0-08 of a line, agree perfectly with the racemose glands of the oral 

 cavity and oesophagus. Their secretion is an alkaline mucus, in which 

 no formed elements are contained, having no digestive action upon 

 coagulated protein compounds and probably merely subservient to 

 mechanical ends. 



The tubular, or Lieberkiihnian glands (cryptce mucosoe), are distri- 

 buted over the whole small intestine, including the duodenum, as innu- 

 merable, straight, narrow caeca, which occupy the entire thickness of 

 the mucous membrane and are frequently slightly enlarged at their ex- 

 tremities, though hardly ever dichotomously divided. The best idea of 

 their number is obtained by viewing the mucous membrane, either from 

 above or in vertical section, under a low power. In the latter case, we 

 see the cseca standing close together, almost like palisades (Fig. 206) ; 

 in the former, we observe that the glands do not occupy the whole sur- 

 face, but only the interspaces between 

 the villi : here, however, they exist in 

 such numbers, as to leave no intervals 

 of any width, the mucous surface 

 between the villi appearing pierced 

 like a sieve. Even on Peyer's patches 

 and over the solitary follicles, these 

 glands are to be met with ; but in man, 

 they leave those portions of the mu- 

 cous membrane which lie immediately 

 over the centre of the follicles free, 

 and therefore are arranged like rings 

 around the follicles. The length of 

 the Lieberkiihnian glands equals the 

 thickness of the mucous membrane and 



FIG. 212. Lieberkiihnian glands of the Pig, magnified GO diameters: a : membrana propria 

 and epithelium ; 6, cavity. 



Fig. 212. 



