258 



THE HUMAN MECHANISM 



Vestibule with Openings 

 of Semicircular Canals 



Scala Vestibuli 



Cochlea 



Eustachian Tube*^-. 



FIG. 102. Diagrammatic representation of the 



membranous labyrinth of the cochlea in relation 



to the structures shown in Figs. 100 and 101 



The scala vestibuli and scala tympani are the two 



portions of the bony cochlea which inclose the 



membranous cochlea 



21. Taste and smell. The end organs of taste are small 

 rounded eminences, or papillce, on the dorsal surface of the 

 tongue, and from these the fibers of the nerves of taste pass 

 to the brain. The end organs of the nerve of smell are situ- 

 ated in the upper portion of the nasal cavity and consist 

 of delicate cells very sensitive to the presence of odors. 

 Sensations of taste are frequently confounded with those of 

 smell. An onion, for example, has little or no taste, as can 



be shown by placing 

 a bit on the tongue 

 when one is holding 

 the breath ; none of 

 the flavor of the 

 onion is perceived. 

 On the other hand, 

 sour, sweet, bitter., 

 Scala'Tympani and salt are true 



sensations of taste. 

 This unconscious 

 blending of tastes 

 with odors in form- 

 ing our ideas of the 

 nature of objects re- 

 calls the formation of visual judgments by the combination 

 of retinal sensations with those aroused by the muscular 

 act of converging the eyeballs. 



22. Cutaneous sensations. The skin is the place of origin 

 of at least three sensations touch, cold, and warmth. These 

 sensations are distinct, as is shown by the observation that 

 on certain points of the skin some*of them may be felt, but 

 not others. This fact is usually interpreted to mean that 

 each sensation has its own set of end organs and nerve 

 fibers. Especially striking is the fact that warmth and cold 

 are not felt by the same spot of skin, which seems to prove 

 conclusively that they are separate sensations. 



