GUSTATORY SENSATIONS. 



917 



the glossopharyngeal nerve. (4) It is uncertain whether the hard 

 palate also possesses the sense of taste ; it is usually said not to be present 

 in the middle of the tongue. 



The end-organs of the gustatory nerves are the taste-buds or taste-goblets 

 discovered by Schwalbe and Loven. These are found on the lateral surfaces of 

 the circumvallate papillae (Fig. 331, I) facing the capillary cleft R R of the sur- 

 rounding furrow, more rarely on the surface of the papillae, and on the, opposite 

 side of the furrow. They occur also on the fungiform papillae, on the papillae 

 of the soft palate and on the uvula, but also on the under surface of the epi- 

 glottis, the upper portions of the posterior surface of the larynx and the inner 

 aspect of the arytenoid cartilage, and on the vocal bands. Many of these buds 

 are said to disappear with age. The gustatory goblets, 81 // high and 33 /u thick, are 

 bud-shaped or barrel-shaped cellular structures, embedded in the thick squamous 

 epithelium of the tongue. The outer portions are made up of curved, fusiform, 



FIG. 331. I, Transverse Section through a Circumvallate Papilla: W, the papilla; \i v } , the wall in section; R R, 

 the ring-shaped cleft; K K, the taste-bud in position; N N, nerves. II, Isolated taste-bud; D, cortical 

 portion; K, lower extremity; E, free open extremity, with projecting tips of the taste-cells. Ill, Isolated 

 cortical cells (d) and taste-cells (e). k 



nucleated investing or supporting cells, like the staves of a barrel (Fig. 331, II, 

 D; isolated III, d). Toward the free surface they surround an opening, the 

 porus, and beneath this a small depression. Surrounded by these cells, in the 

 axis of the bud, there are from one to ten taste-cells (II, E), some of which possess 

 a delicate process at their upper extremity (pin-cells III, e), while others do not 

 (rod-cells). The gustatory nerves lose their myelin-sheaths, and form plexuses, 

 always ending free in the taste-buds, either by surrounding the buds with 

 delicate fibrils on the outer side like a basket or by penetrating their interior. 

 They terminate, ultimately, free, on a level with the opening of the taste-bud. 

 After section of the glossopharyngeal nerve, the taste-buds degenerate within 

 thirty hours, and the protecting cells are converted into ordinary epithelial cells in 

 the course of twelve days. Leydig found in the skin of fresh-water fishes goblet- 

 shaped organs similar to the taste-buds. 



The glands of the tongue, to which the ninth cranial nerve sends secretory 

 fibers, are discussed on p. 256; the follicles likewise. 



GUSTATORY SENSATIONS. 



There are four different qualities of taste: the sensations of sweet, 

 bitter, sour and salty. Sour and salty substances irritate also the 

 sensory nerves of the tongue. In greatest dilution, however, they 

 stimulate only the endings of the specific nerves of taste. In all proba- 

 bility a special perceptive fiber exists for each quality of taste (in 

 accordance with the doctrine of the specific energies). 



