288 On (he Sense of Feeling: 



themselves, so as at ouce to embrace the whole superficies. It is therefore a 

 mechanical adaptation, and not the addition of a new sense, which enables 

 us to obtain ideas of figure ; although indeed such parts, as for instance the 

 hands and feet, are found to possess common sensibility in a very high 

 degree. It is not because there is a greater supply of nerves at the ex- 

 tremities of the fingers, than in any other part of the body, nor because 

 the hand is endued with the most delicate sense of touch, since it is 

 surpassed by the lip and other parts, that it is the principal organ of feel- 

 ing ; but simply because from its peculiar mechanism, it is tiie only organ 

 which can give us correct ideas of figure ; and hence the natural distinction 

 between ' lad,' the mere sensibility, and ' touch,' its mechanical applica- 

 tion to the forms of bodies. Tact is a passive, — touch an active sense. 



But there is another property of matter of which tact is cognisant, that 

 of temperature. The sense of heat and cold is perfectly distinct from that 

 of form and solidity, although exercised by the same organ. This sense, 

 however, is only relative, and depends entirely upon the quantity of caloric 

 gained or lost by us in a given instant, compared with that gained or lost 

 in the instant preceding, without any reference to the absolute temperature 

 of the foreign body. Cpeteris paribus, it is indeed true that bodies of a 

 higher temperature than our own feel hot, and of a lower, cold ; never- 

 theless, if after touching a very cold body, we touch one that is less so, 

 we find it warm, although in truth its temperature is below the general 

 temperature of our own frame. It is for this reason that cellars and cathe- 

 dral churches feel warm in winter, and cold in summer ; while, in fact, 

 they only preserve an equable temperature throughout. The relative con- 

 dition of tact is well illustrated by the old story of the ascending and 

 descending travellers upon the Alps ; or, as the experiment may be more 

 conveniently tried at home, with three basins of water. 



But although the anatomist cannot distinguish more than one set of ner- 

 vous filaments on the surface of the body, for these modifications of the 

 general sense, the pathologist, who studies the animal frame under the dis- 

 severing effects of disease, can shew that such a distinction exists. 



There is a disease, in which the patient is able to grasp and estimate 

 the figure of any body, but is utterly unable to appreciate its temperature. 

 Such persons have been known to grasp a hot poker, or to plunge the hand 

 into boiling water, and ifter a certain time to withdraw it, perfectly un- 

 conscious of pain, but with the member covered with blisters. 



Tact, then, places us in immediate communication with the external 

 world, far surpassing, in this respect, the senses of hearing and sight, 

 which require an intermediate substance for their exercise, and are not 

 only very liable to error, but are often corrected by the tiict. I heard it, 

 is good evidence ; I saw it, is better ; but, I felt it, is tolerably con- 

 clusive. 



But this sense is not absolutely infallible. We are accustomed to refer 



I 



