20S 



MUCOrS MEMBEAXES. 



Fig. 133. 



of both is very different in different parts. In some situations, as in the 

 gullet, windpipe, bladder, and vagina, the filamentous connective tissue 

 is abundant, and extends throughout the whole thickness of the fibro- 

 vascular lawyer, forming a continuous and tolerably compact web, and 

 rendering the mucous membrane of those parts comparatively stout and 

 tough. In tlie stomach and intestines, on the other hand, where the 

 membrane is more complex, and at the same time weaker in structure, 

 the elastic fibres are wanting and the white connective tissue is in small 

 ]iroportion ; its principal bundles follow and support the blood-vessels, 

 deserting, however, their finer and finest branches which lie next the 

 basement-membrane ; and accordingly there exists, for some depth 

 below this membrane, a stratum of the corium in which very few if any 

 filaments of the common areolar tissue are seen. In this stratum of 

 the gastro-enteric mucous membrane, the tubular glands with their 

 lining epithelium are set, and between and around them the numerous 

 sanguiferous capillaries and lymphatic vessels are distributed ; but the 

 substance of the membrane in which these parts lie is constructed of 

 retiform connective tissue, which is formed of ramified and reticularly 

 connected corpuscles, with or without nuclei persistent at the points 

 whence the branches divaricate ; and in the meshes of this tissue 

 is contained a profusion of granular corpuscles, like those in the 



lymphatic glands. This structure 

 nig. 137 and 138 </), which prevails in 

 the mucous membrane of the stomach 

 and intestines, both large and small, as 

 well as in some other parts, is named 

 lymphoid tissue from its resemblance 

 to the interior tissue of the lymphatic 

 glands, and of other bodies belonging 

 to or supposed to belong to the lym- 

 phatic system, and especially those 

 known as the solitary and agminated 

 glands of the alimentary mucous mem- 

 brane. The tissue forming the last- 

 named bodies, indeed, is often con- 

 tinuous with the lymphoid tissue in 

 their vicinity. 



The deepest layer of the riiucous 

 membrane is formed usually by non- 

 striated muscular tissue, and is named 

 miiscularis mucosce. This lies next to 

 the submucous tissue, and consists of 

 bundles running in many parts both 

 longitudinally and circularly, in others 

 in one of these directions only. Pro- 

 longations from it pass up between the 

 glands to be distributed in the villi. 



Fapillse and villi. — The free sur- 

 face of the mucous membranes is in 

 some parts plain, but in others is beset with little eminences named papilke 

 and villi. The papilke are best seen on the tongue ; they are small pro- 

 cesses of the corium, mostly of a conical or cylindrical figure, containing 

 blood-vessels and nerves, and covered with epithelium. Some are small 





Fig. 138. — Lymphoid or Retiform 

 Tissue of the Ixtestinal Mucous 

 Membrane of the Sheep (from Frey). 

 Magnified 400 Diameters. 



Cross section of a small fragment of 

 the mucous membrane, including one 

 entire crypt of Lieberkiilm and parts of 

 several others : a, cavity of the tubxilar 

 glands or crypts ; b, one of the lining 

 epithelial cells ; c, the lymphoid or reti- 

 form spaces, of which some are empty, 

 and others occupied by lymjih-cells as 

 at d. 



