46 



MANUAL OF PHYSIOLOGY. 



which it is placed. Some tracts are covered with fine moving 

 hair-like processes, called cilia, which give rise to a slight motion 

 of the fluids in contact with them. 



FIG. 11. 



FJG. 12. 



FJG. 11. Two cells of scaly epithelium from the inside of the cheek. (Ranvier.) 

 FIG. 12. Section of milk gland of cat, showing secreting cells containing fat globules, 

 and some secretion in alveoli. 



Other differences will be given in detail with the description of 

 the duties of the many mucous surfaces. The most striking, and 



FIG. 14. 



FIG. 13. 



Fio. 13. Ciliated epithelial cells from the gills of mussel. (Cadiat.) 



FIG. 14. Stratified ciliated epithelial cells from the trachea of man. (Cadiat.) a. 



Large surface cells, with cilia on surface, b. Lower cells in earlier stage of development. 



e. Cell charged with mucus. 



at the same time the most interesting, modifications are those 

 in the special sense organs, where the cells are in immediate 



