500 THE INTESTINAL CANAL, BY E. KLEIN AND E. VERSON. 



divided, but occasionally bifid or trifid papillae, which often, 

 coming into contact at their wide bases, project into the epithe- 

 lium; the longest of these (0'525 0*63 of a millimeter in length) 

 are situated at the commencement of the muco-membranous 

 portion posteriorly; coincidently with the diminution in the 

 thickness of the epithelium they likewise become shorter, and 

 do not exceed half the depth of the epithelium. 



The epithelial cells covering the papillae are arranged in an 

 imbricated manner, and are much natter than the cells situated 

 on the same level between the papillae. Corresponding to the 

 first two or three rows of papillae situated at the commence- 

 ment of the muco-membranous portion, the epithelial surface 

 presents a small elevation ; and in newly born children the 

 papillae of this part of the lip, and those at the angles of the 

 mouth, project as much as one millimeter beyond the lower 

 plane of the epithelium. 



The glands that are situated in the submucous tissue of the 

 muco-membranous portion make their first appearance behind 

 the most prominent portion of the convexity of the lip, and, 

 indeed, at that point where the epithelium begins to be con- 

 stant in thickness. 



They constitute acinous glands that are essentially similar to 

 the salivary glands. Our knowledge, however, is not sufficiently 

 advanced to enable us to state that they present those charac- 

 teristics of the salivary glands which have been the subject of 

 recent investigation. They open on the surface of the mucous 

 membrane or epithelium by means of small excretory ducts. 

 Each of these is a canal bounded by a structureless membrane, 

 in which the laminae of tesselated epithelium only extend to the 

 depth of the epithelial layer generally ; beyond this it is lined 

 by a single layer of cylindrical epithelium. After pursuing a 

 spiral course obliquely through the membrana mucosa it gives 

 off numerous branches, which frequently divide and terminate 

 in the individual acini. The acini belonging to a large branch 

 are united into a lobule by the fasciculi of the submucous con- 

 nective tissue, and these again are formed into lobes. The 

 fasciculi and fibres which limit a lobulus or a lobe, and 

 in the meshes of which the several acini are imbedded, are 

 continued as a sheath to the excretory duct in its passage 



