MEMBRANES AND GLANDS. 101 



are usually provided with goblet cells, whose function is to produce 

 mucus. With squamous stratified epithelium,, the mucus is usually 

 produced by glands located in the stroma, (2) Basement mem- 

 brane. This occurs as a mere line beneath the epithelial layer. It 

 is sometimes called the membrana propria, It is made up of flat- 

 tened cells, either united edge to edge, or held together by anasta- 

 mosing processes. On one side, this membrane supports the epithe- 

 lium ; while on the other, it is in close connection with the capil- 

 laries. (3) The stroma. This structure lies directly beneath the 

 basement membrane, and is composed of fibrous connective tissue 

 and elastic fibres, and is provided with a rich supply of blood-vessels 

 and lymphatics. (4) The Muscularis mucosce. This is a shallow, 

 muscular sheath, which forms the lower limit of the mucous 

 membrane. It is composed of circular and longitudinal strata 

 of involuntary muscle fibres. (5) Occasional structures. In. addi- 

 tion to the structures above named, papilla?, villi, glands, and lym- 

 phoid cells occur in the mucous membrane. Papillce are conical ele- 

 vations of the stroma, which are supplied with blood-vessels and 

 nerves, and covered with epithelium. They occur in the tongue, 

 oesophagus, etc. The villi occur chiefly in the small intestine. 

 They are provided with blood capillaries and lacteals, and are de- 

 signed to increase the absorbing surface of the intestine. The 

 glands which occur are of two varieties tubular and sacular. The 

 mucous glands are located in the epithelial layer and stroma of 

 mucous membranes, and are concerned in the elaboration of mucin. 



IT. GLANDS. 



Glands are of two kinds serous and mucous. A serous gland is 

 characterized by spherical, granular cells, with central nuclei, which 

 are readily stained by carmine. Mucous glands are not readily 

 stained by carmine. The nuclei are usually upon the cell surface. 



OUTLINE OF GLANDS. 



f Serous glands. 



Kinds \ 



[ Mucous glands. 



