G. THE RECTUM, BY E. VERSON. 585 



till the transition into the ordinary tesselated epithelium is 

 completed. In the child this transition is less sudden, because 

 the projecting angles of the folds of Morgagni are already 

 crowned with the pavement epithelium, though the more pro- 

 tected deep fissures between the columnse always preserve an 

 investment of cylindrical cells. Papillae are first encountered 

 where the pavement epithelium is completely developed that 

 is, immediately below the sphincter internus. 



In the rat the Column Morgagni are absent, and the lowest crypts 

 extend to the sphincter externus. These lowermost crypts are lined 

 throughout by the usual form of columnar epithelium, but on the side 

 of these orifices which is turned towards the anus a layer of pavement 

 epithelium, four or five cells in thickness, immediately abuts upon the 

 cylinder cells, which last reach to the precise level of the orifice. This 

 point coincides always with tbat at which the muscularis mucosae, be- 

 coming oblique, runs out into points and is lost. 



NEEVES. The plexuses both of Meissner and of Auerbach are con- 

 tinued from the colon into the rectum, the development of the latter 

 preponderating over tbe former. After the peritoneal investment 

 ceases, the close nervous web from the plexus pudendalis joins it, 

 containing ganglionic enlargements of considerable magnitude. The 

 above plexuses contain both dark-edged and pale sympathetic nerve 

 fibres, which branch and are distributed between the muscular fas- 

 ciculi of the sphincter internus and externus, and those of the external 

 longitudinal muscular layer and levator ani. 





