HISTOLOGY 



91 



(2) A glandular epitheliiun is one in which secreting cells are scattered 

 more or less abundantly throughout the layer. (Fig. 80, 11) 



Gustatory Pore Sustentacular 

 cell canal cell 



Pore canal Sustentacular Pore Gustatory 



(cut obliquely) cell canal cell 



Connective tissue 

 of tunica propria 



Fig. 84. — Taste-buds from a vallate papilla of the human tongue; as seen in section 

 perpendicular to the surface of the epithelium. S is a diagrammatic representation 

 of the structure of one "bud." X475. (From Morris, "Human Anatomy.") 



(3) In a sensory (or neuro-) epithelium certain cells are specialized 

 for reception of stimulation by some agency in the cell's environment 

 (Fig. 83). EpitheHal sensory cells may be grouped in clusters to form 

 sense organs (Fig. 84). An epithelium may 

 be rendered sensory by free nerve termina- 

 tion, that is, the terminal twigs of a 

 nerve fiber ramifying amongst the epithe- 

 lial cells (Fig. 85). These nerve fibers, 

 however, are not produced by the epithe- 

 lium itself but invade it from adjacent 

 tissue. 



(4) Cilia are extremely delicate motile ' 



filaments borne by the free ends of epitheHal ation in the epiderm^rof^'^S^la- 



Cells. A single cell mav carry from one ^^ndra. (From Kingsley. after 

 ' ... Retzius.) 



to over a hundred. A cmated epithelium 



is one in which some or all of the cells carry cilia. (Figs. ^SE, 79) 



Cilia and mucous glands commonly occur in the same epithelium. 

 The simple external epithelium of an earthworm and the stratified epider- 

 mis of a fish combine cuticular, glandular and sensory specializations. 



Glands 



" Glands " whose products are as different as are sweat, eggs and blood- 

 cells hardly merit the same name. Accepting the name, it is necessary 



