the skin that is touched. A lighter pressure can be felt on the forehead and temples than with any part of the body. (Why is it best for this to be the case?) The greatest delicacy in locating the point of the skin touched is found to be located in the tip of the tongue, the lips, and the ends of the fingers (Exp. 1). (Why is it best that this is so?) This delicacy is least in the middle of the back. The delicacy varies with the number of touch corpuscles in different parts of the skin. The sense of touch is capable of great cultivation, as in the case of the blind.
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Fig. 120.—different Kinds of Touch Bodies at Ends of Nerves.
A, from cornea of the eye; B, from the tongue of a
duck; C, D, E, from the skin of the fingers. (Jegi.)
The temperature sense is given by special nerves called the thermic
nerves (Exp. 2). That the thermic nerves are easily fatigued is noticed
soon after entering a bath of hot water; it is also shown by the fact
that in cold countries the nose or ears of a person may freeze without
his feeling it.
The Muscular Sense.—The special sense of touch gives some sense of weight. A weight upon the skin must be increased by one third before it feels heavier, but by lifting an object so as to bring into action the muscular sense residing in nerves ending in the muscles an increase of only one seventeenth of the original weight can be noticed (Exp. 3). This sense gives us a continual account of the position of the limbs (Exp. 4).
The end organs of taste are located in the papillæ of
the tongue. The tongue has a fuzzy look because of the
numerous papillæ.
