262 



HISTOLOGY 



tastes. The " taste " of our food is largely composed of olfactory im- 

 pressions from the nose. 



In structure the specific cells of the gustatory tissues are very different, 

 in the vertebrates, from those of the olfactory organs. Their discharging 

 end is not the extremity of a process extending into the brain. Instead, 

 the centripetal end of the cell body is rounded, and the receiving nerve 

 cells in the nerve center send afferent nerve fibers to the gustatory cells 

 to receive the stimulus from the cell body. 



The gustatory cells are not found scattered among an epithelium as 

 are the olfactory cells, but associated in small numbers with certain 

 supporting cells that somewhat resemble them in shape. Both of these, 

 in the vertebrates, may be looked upon as simple columnar epithelial 

 elements that were prevented by their function from developing, along 

 with the rest of a former simple epithelium, into the stratified form. 

 These small collections of taste cells, with their supporting cells, form 

 structures known as "taste buds " and are to be found in various parts of 

 the mouth in the higher vertebrates ; while in the Amphibians and fishes 

 they enjoy a wider distribution, even out to the face and head or on 

 fin-rays and barbies developed for this purpose. In man they are to be 

 found on the vallate papillae, the sides of the tongue, and on the outer 

 surface of the epiglottis. 



The specific cell of the tissue is a thin and elongated epithelial form 

 reaching from the surface to the basement membrane where, unlike 



the olfactory cell, it ends. The 

 cell is somewhat enlarged at its 

 middle or lower part to contain 

 the nucleus. Its distal end bears 

 a short rod-like structure, the cell- 

 organ of perception (Fig. 230). 

 There is but little variation in the 

 shape of this kind of cell through- 

 out the vertebrate groups. One 

 can see it thinner and longer in 

 the skin of Lamperta, or shorter 

 and thicker in the skin of several 

 fishes. Its arrangements as a tis- 

 sue with the accessory supporting 

 FIG. 23 o. -Taste bud in tongue of man. g .c., cells is more interesting. The two 



gustatory cells; sup.c., supporting cells; nv.fi., together form isolated groups, with 



the specific cells tending toconcen- 

 trate at the center of each group. 

 A rather diffuse group of this kind is formed in the larval form of 

 Petromyzon. In this case the thread-like taste cells are scattered 



g.c. 



sup 



