THE SPECIAL SENSES 275 



training, also, the physician acquires the tactus eruditus, or 

 discriminating touch ; but among the blind, delicacy of touch 

 is most remarkable, and it there finds its highest value ; for 

 its possession, in a measure, compensates for the loss of sight 

 by enabling them to read, by means of raised letters, to work 

 with certain tools, and even to play upon musical instruments. 

 A person born without sight, and without hearing or voice, 

 may, by the education of the touch, be rescued from apparent 

 imbecility, and be taught not only to read and write, but even 

 to perform household and other useful labors. 



27. Sensations of Temperature and Weight. Each of these 

 sensations has been described by the physiologists as a special 

 sense, and they are rival candidates, so to speak, for the posi- 

 tion and title of the sixth sense. In the sensation of temper- 

 ature, or the thermal sense, touch bears a part, but the two 

 feelings appear to be distinct. In proof of this, we observe, 

 firstly, that they are not alike intense in the same situations ; 

 as, for example, the skin of the face and elbow, where the 

 sense of touch is feeble, is very sensitive to impressions of 

 heat and cold. Secondly, the ability to recognize temperature 

 may be lost by paralysis, while the sensibility of touch remains 

 unaffected. When the skin comes in contact with a very hot 

 substance, the sensation felt is that of pain not of touch. 

 In like manner, a very cold substance causes pain, not the 

 feeling of cold. So that a red-hot iron, and solid carbonic acid 

 (the temperature of which is 108 below zero), feel alike ; and 

 each, if pressed slightly, will produce a blister. {Read Note 4.) 



4. Qualities Determined by the Sense of Touch. "The eye, by 

 the aid of certain signs, is often able to tell whether a body is hot 

 when, for instance, it is glowing or steaming but a perception of 

 warmth is not possessed by the eye. This is had by the skin alone, 

 and it is of great importance to our preservation that this property is 

 spread over the entire surface ; for it surrounds the body like a pro- 

 tecting wall against its worst enemy cold which, if not thus guarded 

 against at all points, would speedily destroy life. We are warned, how- 

 ever, of the approach of the enemy by a common sensation of the 

 skin, and an inward chill, which is only caused by a coolness of the 



27. Rival candidates for the sixth sense ? Give the two reasons on the subject. 



