GUSTATORY AND OLFACTORY TISSUES 



26l 



cells, with their round, clearer, nucleated bodies below the level of the 

 lowest nuclei of the sustentacular cells. The well-rounded nuclei almost 

 fill this cell body (Fig. 228, sen. c). Some few have the body up in the 

 outer third of the epithelium. They give the lower third of the epithe- 

 lium a distinctly lighter appearance. 



The cell body is drawn out distally into a thin, smooth process that 

 reaches to the surface and acts as the perceptory organ. Perceptory 

 rods or hairs are not to be distinguished. The perceptory process is thin- 

 ner than the distal processes of the sustentacular cells, but not so thin as 

 the proximal portion of the cell to which it belongs, which is drawn 

 out into a much thinner and longer 

 process, the centripetal nerve fiber. 

 This fiber, which is never myeli- 

 nated, passes entirely out of the 

 epithelium, and running through 

 connective tissue and bone, it ends 

 in the central nervous system, as 

 in man, in the olfactory bulb. 

 Here the fibers, in mammals, end 

 in peculiar round bodies known as 

 the glomeruli. These are not cel- 

 lular structures, but are formed by 



nv.f. 



the branching ends of the fibers FIG. 229 .- Silver picture of the olfactory cells 

 from the Olfactory Cells United with in the nasal epithelium of Tropidonotus. 



similar branching end-organs from ^"EST^^S"*' "* ""* 



nerve cells in the bulb, the mitral 



cells, and others. Figure 229 shows these relations by means of the 



silver process used on an embryonic Tropidonotus. 



The relation of the olfactory cell to the second kind of chemico- 

 perceptory cell that we shall study, the gustatory cell, or cell of taste, 

 is a close one as regards function. In regard to its origin and structure, 

 however, it may be strongly contrasted with it. Both perform the same 

 function, but do so in different ways and attain different results. The 

 olfactory cells deal with the finely divided atoms or molecules of sub- 

 stances in a gaseous state and usually dissolved in air or water. The 

 gustatory cells, at least those of man, require more crude masses of the 

 substance and require an immediate contact with them. Also they 

 most probably must always be dissolved in water or some fluid of which 

 water is a part. 



The result is less definitive and delicate from the stimulation of a 

 gustatory cell. We cannot, in this way, detect fine flavors and aromas, 

 as can be done from olfactory cells, but secure only a few coarse impres- 

 sions as sweet, sour, bitter, the warmth impression of alcohol, and such 



