24 



HAND-BOOK OF PHYSIOLOGY. 



secreting glands, and hence are often termed glandular; they are gener- 

 ally more or less rounded in outline: often polygonal from mutual pres- 

 sure. 



FIG. 18. Peritoneal surface of septum cisternse lymphaticae magnae of frog. The stomata, some 

 of which are open ; some collapsed, are surrounded by germinating endothelium. (Klein.) x 160. 



Excellent examples are to be found in the liver, the secreting tubes of 

 the kidney, and in the salivary and peptic glands (Fig. 19). 



3. Columnar epithelium (Fig. 20, A and B) lines (a.) the mucous mem- 

 brane of the stomach and intestines, from the cardiac orifice of the stomach 

 to the anus, and (b. ) wholly or in part the ducts of the glands opening on 



FIG. 19. Glandular epithelium. A, small lobule of a mucous gland of the tongue, showing nu- 

 cleated glandular spheroidal cells. B, Liver cells. X 200. (V. D. Harris.) 



its free surface; also (c.) many gland-ducts in other regions of the body, 

 e.g., mammary, salivary, etc.; (d.) the cells which form the deeper layers 

 of the epithelial lining of the trachea are approximately columnar. 



It consists of cells which are cylindrical or prismatic in form, and con- 

 tain a large oval nucleus. When evenly packed side by side as a single 

 layer, the cells are uniformly columnar; but when occurring in several 

 layers as in the deeper strata of the epithelial lining of the trachea, their 



