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Froceedings of the Royal Society 
travelling rapidly into tlie internal ear cause the structures there (the 
basilar membrane and rods of Corti) to vibrate,, and- — as we are 
aware from our knowledge of the action of one vibrating body upon 
another — they do this very rapidly. 
Tar otherwise with the senses of smell and taste. When odorous 
particles pass into the olfactory or upper part of the nasal cavity — 
in which the nerves of smell are placed — it is by diffusion from the 
lower or respiratory part of the nose. If the breath be held, and a 
piece of incense paper be burnt in front of the face, some time may 
elapse before the scent is perceived, because the odorous particles 
have ill fact to diffuse into a closed sac. If, on the other hand, the 
experimenter “ sniffs ” the air, the stimulus will be more rapidly 
perceived, because the odorous particles are carried rapidly through 
the lower chamber of the nose, inducing out-currents from the 
upper chamber, which consequently becomes immediately filled by 
odorous particles. In like manner, the closed sac has to get rid of 
odorous particles from within it by this same slow process of 
diffusion, before the odour ceases to be felt. From the nature of 
the stimulation and position of the end-organ, the limitations in 
time of the sensations are not well marked. 
In the case of the sense of taste, the same holds true. Substances 
held in solution are alone tasted; the tongue is covered with a layer 
of mucin derived from mucous and salivary glands, and the nerves 
are not superficial but embedded in the epithelial covering. It 
will be easily understood, that in this case also, the accession of a 
sensation must, from the nature of the stimulus, and the position of 
the end-organ, be gradual in its production and slow in passing off, 
and therefore not strictly limited in time. The watery solution 
has to mix in the first place with the mucin covering the tongue 
before it can reach the end-organs situated in the epithelium. 
In the case of hunger again, the limitations in time are due 
entirely to a condition of things other than mental. The fulness 
of the alimentary canal is associated with a feeling of comfort, and 
when no food is present therewith a feeling of hunger ; and as there 
is every conceivable transition between a condition of full stomach 
and an empty one, so the passage of the one sensation into the other 
must pass through innumerable transition states. 
If it be needed, another example may be mentioned in the case 
