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



In infants the mucous membrane exhibits a great number of 

 oblong nucleated elements, the extremities of which are drawn 

 out into fine pointed processes which penetrate between the 

 fibres of the tissue. This peculiarity may be observed in several 

 parts of the above-described portions of mucous membrane, 

 and appears therefore to be characteristic of an embryonic con- 

 dition of he tissue. Wherever the epithelium is laminar and 

 tesselated, numerous papillae, narrow at their base, and clavate 

 at their free extremity, project from the surface of the mucosa, 

 and penetrate the epithelial layers to about half their depth ; 

 but where the epithelium of the roof of the pharynx is lami- 

 nated, and composed of cylinders supporting cilia, the papillae 

 are altogether absent. 



The large 'vessels form a plexus beneath the epithelium, giv- 

 ing off finer branches, which either pursue a longer or a shorter 

 course parallel to the surface, or form loops immediately be- 

 neath the epithelium. In the middle third of the membrane 

 in adults, and especially in the lower parts, are numerous pa- 

 pillae arranged with tolerable regularity. In the upper parts 

 they are in some parts imperfectly developed, and here and 

 there are altogether absent. In the lower third the papillae are 

 both constantly present and numerous. 



In the infant the papillce are only feebly developed, either 

 in the form of slight sinuosities of the mucous membrane 

 projecting into the epithelial layers, or as sharply pointed 

 papillary elevations composed of connective tissue and blood- 

 vessels, especially over those parts of the membrane present- 

 ing striae or folds, which penetrate to a variable extent into the 

 epithelium. 



As it approximates the muscular tissue the structure of the 

 mucous membrane becomes looser, forming the submucous tis- 

 sue ; and the fasciculi, which constitute a plexus with meshes 

 of various sizes, are arranged in the upper and middle third in 

 a horizontal direction, or run obliquely backwards and out- 

 wards between the fasciculi of the muscular layer to the outer 

 fibrous layer, as well as in the opposite direction from this in- 

 wards and downwards, some few fasciculi penetrating between 

 the muscles into the submucosa, in which they are gradually 

 lost as they descend. In the lower third, the fasciculi of the 



