THE SENSE OF FEELING. 269 



thickness of the envelope which occasiong the difference. The thicker the 

 epidermis, the more slowly does the sensation of warmth or cold penetrate to 

 the nerve-ends inbedded in the cutis. In the human hand the thickness of the 

 epidermis is much more considerable in the palm than on the back ; when, 

 therefore, we immerse our hand in cold water, the sensation of cold is sooner 

 perceived in the back than the palm ; but, because a proportionably larger num- 

 ber of nerves terminate in the latter, the feeling eventually reaches a greater 

 degree of intensity in the palm than the back of the hand. The difference of 

 two temperatures isT however, appreciable with competent exactness by the 

 sense of touch, notwithstanding the sources of error which have been noticed ; 

 if we take two vessels with water of different temperatures and in quick suc- 

 cession, dip the same fiuger first in one and then in the other, we can distinguish 

 which is the warmer, which the colder, if the difference be only a fraction 

 (1 — 1) of a degree. But the delicacy of discrimination is not the same with 

 all persons, and practice greatly improves the exercise of this sense. It is 

 further to be remarked that we habitually give ohjeclivily to our perceptions of 

 temperature, as we do to those of pressure, and to all true perceptions of the 

 eense in question. If we touch an object which abstracts heat from the skin, 

 it is not the mere subjective sensation, not the idea of a change r.f temperature 

 in the skin, which presents itself to our consciousness, but the immediate idea 

 of the cold object, to which we impute as a property that quality of our own 

 sensation which we denominate coldness. Only in the case wlien no sensation 

 of pressure accompanies that of temperature, and the skin therefore gives us no 

 perception of an exciting object, are we sensible of the coldness as something 

 subjective, as a state of our own sentient organism. 



We turn now, in the third place, to the sense of place or position — that is, the 

 faculty of our organs of touch which gives us a perception of the situation, size, 

 and form of the jyortions of the shin on wliich cither pressure, or heat or cold, 

 takes effect. It has already been cursorily noticed by what steps we arrive at 

 the ideas of position which are connected with the sensation of touch ; and we here 

 recall the most important particulars. First of all, it is to be observed that 

 there is no room for supposing a direct primary sensation of place ; the new-boru 

 child feels at first only the simple sensation of pressure, without learning there- 

 from that the skin is the place whence the sensation was excited, or recognizing 

 the part of the skin on which the excitation was produced; it, as yet, knows not 

 that it possesses in its skin an outspread organ composed of so many distinct points 

 of sensibility. It is easy to comprehend, moreover, that it cannot be the cours3i 

 of a nerve-fibre which furnishes the idea of place ; that hence it cannot be that 

 simply because some particular nerve terminates in the leg, for instance, the . 

 idea of pressure of the leg connects itself with the sensation generated by that 

 nerve ; in the mere course of the nerve there can be nothing to determine the 

 nature of the resulting idea, nothing to qualify the excitation which acts upon 

 the mind. If the process in the nerve-fibre be the same, the sensation produced 

 will also be the same, whatever may be the direction in which the nervous current 

 is conducted to the brain ; just as the movements of the hand of the electro-mag- 

 netic clock continue the same, whatever the direction of the conducting wire ; 

 the movements furnish no indication of the origin of the operating current. If, 

 therefore, the sensation itself gives occasion for the formation of ideas of place, 

 we are obliged to suppose that through some modidcation a slight but constant 

 peculiarity exists for each separate fibre which is stimulated, and that thus the 

 sensation which is effected by exactly the same cocnpression possesses a some- 

 what different shade when it proceeds, not only from widely separated uervea 

 of the arm or leg, but also from two fibres termininating in close proximity with 

 one another. These presumed peculiarities of the currents in separate fibres of 

 the nerves wo have above indicated by the name of local tokens. Through 



