COLUMNAE EPITHELIUM. 31 



become detached in teased preparations. The protoplasm of the cell is 

 highly vacuolated and reticular, and fine longitudinal striae may be seen 

 in it, which appear continuous with the striae of the free border. The 

 nucleus (n) is oval and reticular. The lateral borders of the cells are 

 often somewhat irregular or jagged, the result of the pressure^ of^ 

 amoeboid lymph-cells, which are generally found between the columnar 

 cells, at least in the intestine. After a meal containing fat the cells may 

 contain fat-globules, which become stained black in the osmic pre- 

 paration. 



FIG. 28. A ROW OF COLUMNAR CELLS FROM THE INTESTINE OF THE RABBIT. 

 Smaller cells are seen between the epithelium-cells ; these are lymph-corpuscles. 



Columnar epithelium-cells are found lining the whole of the interior 

 of the stomach and intestines : they are also present in the ducts of 

 most glands, and sometimes also in their secreting tubes and saccules. 

 The epithelium which covers the ovary also has a modified columnar 

 shape, but cells having all the structural peculiarities indicated above 

 are found only in the alimentary canal and in its diverticula. 



I. 



FIG. 29. COLUMNAR EPITHELIUM-CELLS OF THE RABBIT'S INTESTINE. 



The cells have been isolated after maceration in very weak chromic acid. The cells are much 

 vacuolated, and one of them has a fat-globule near its attached end ; the striated border 

 (str) is well seen, and the bright disk separating it from the cell-protoplasm ; n, nucleus 

 with intranuclear network ; a, a thinned-out wing-like projection of the cell which prob- 

 ably fitted between two adjacent cells. 



Goblet-cells. Some columnar cells, and also cells of glandular, 

 ciliated and transitional epithelia, contain mucigen, which is laid down 

 within the cell in the form of granules (fig. 33, m\ m 2 ) and may 

 greatly distend the part of the cell nearest the free border. When the 

 mucigen is extruded as mucus, this border is thrown off, and the cell 

 takes the form of an open cup or chalice (fig. 30 and fig. 33, m 3 ). 



