264 



THE ORGANS 



columnar cell, the younger cells being indifferent as it were and 

 able to become columnar cells or goblet cells as conditions may re- 

 quire. Again opinions differ as to whether the mucous cell, having 

 discharged its secretion, dies or re-secretes, or returns to the condi- 

 tion of the columnar cell. Small spherical cells with deeply staining 

 nuclei are found in varying numbers among and sometimes within 

 the epithehal cells. ^ These are so-called wandering cells, migratory 



Srrz. 



Li©(jR^fe^c^<S^;B: 



k 



\ 





Fig. 167. 



Fig. 166. — Longitudinal Section of Villus from Small Intestine of Dog. (Piersol.) 

 a, Columnar epithelium; b, goblet cells; h, leucocytes; c, basement membrane; d, core of 

 villus; e, blood-vessels;/, lacteal. ^ 



Fig. 167. — Cross-section of a Villus of Human Small Intestine. X530. (Kolliker.) 

 The stroma of the villus has shrunken away from the epithelium, b, Goblet cell; c, 

 cuticula showing striations; e, columnar epithelial cell; gni, basement membrane with 

 nuclei; /, leucocyte in epithelium; /', leucocyte just beneath epithelium; m, large leuco- 

 cyte in stroma; ch, central chyle vessel; g, blood-vessel. 



leucocytes, from the underlying stroma (Figs. 166, //, and 167, /). 

 Other cells with dark-staining nuclei, ^''replacing cells" are found 

 between the bases of the columnar cells (pages 75 and 257). 



In addition to the connective- tissue and lymphoid cells, which 

 constitute the main bulk of the villus core (Figs. 166 and 167), iso- 

 lated smooth muscle cells derived from the muscularis mucosce occur, 



1 DavidofI considers these cells leucocytes in process of formation. He describes 

 some of the columnar cells as having two nuclei, one of which remains within the cell, 

 while the other is extruded with a little cytoplasm as a leucocyte. 



