THE SENSE OF FEELING. 259 



wliole, as the association which, in the mind of a child, connects the physician 

 with the suffering which it is his purpose to relieve. 



Still, were the function of the nerves of feeling limited to the production of 

 pain, we could blame no one for incredulity in regard to their utility. There are 

 a great number, however, of the nerves of feeling, and, indeed, all those whose 

 outer terminations are imbedded in the skin of the general surface of the body, 

 and in the mucous membrane of the cavity of the mouth, which, besides the 

 general feeling of pain under certain conditions, are destined, through a more 

 than ordinary activity, to produce those peculiar modifications of feeling which, 

 from their external causes, we denominate sensations of pressure and tempera- 

 ture, and which, on grounds above indicated, we contradistinguish from the com- 

 mon feeling as true sensations of the sense of touch. The nerves of the outer 

 skin and of the mucous membraae of the mouth we term, therefore, nerves of 

 touch. A pressure applied to the skin gives rise not only to the corresponding 

 sensation of pressure, but to the perception of an object which presses, as well 

 as of its form and size. Touching the skin with a moderately warm or cold 

 body imparts a feeling of warmth or cold. On the other hand, if a muscular 

 part, which likewise possesses nerves of sensation, be laid bare by incision,, 

 there results, not a sensation of pressure, but of pain; not the idea of an in- 

 cisive object, but only a consciousness of subjective hurt ; so, too, from the touch 

 of a hot body there results, not a feeling of warmth, but of pain On what con- 

 "ditions these functional activities of the nerves of the skin depend maybe shown 

 by a simple and easily repeated experiment. These nerves produce the specific 

 sensations of pressure and temperature above referred to, then only, when the 

 external irritants, whether of pressure, of heat, or of cold, operate upon the 

 ends of the nerves existing in the skin, but not when those irritants act upon, 

 the nerve- fibres in their intermediate course between the skin and the Drain. 

 The nerves of sensation which terminate in the skin of a part of the finger be- 

 come combined in their passage to the brain into one stem, which, at the place 

 of the elbow, called by Germans "das Mauschen," runs deep under the outer 

 skin. Now, if we dip the finger of a hand in cold water we perceive a sen- 

 sation of cold ; but if, on the other hand, we immerse the elbow in the same 

 water, though a sensation of cold is at first felt through the skin, after some 

 moments, when the cold has penetrated the skin and reached the nerve-stem be- 

 low, there arises a sensation of pain, which has nothing in common with that of 

 cold, and suggests no idea of an external cold object as cause of the uneasiness. 



How is this to be accounted for? The same irritant operating on the same 

 nerve-fibres, and with so different a result! The difference is founded in this:, 

 that, at the extremities of the nerves on which the cold acts in the skin of both 

 finger and elbow, an organic apparatus exists, which, set in action by the appli- 

 cation of cold, produces in the nerve-fibres a peculiar sort of current, which con- 

 veys to the brain a sensation of cold. If, on the other hand, the cold strikes 

 these nerve-fibres in their passage, it occasions, indeed, an excitation; but, as 

 here the apparatus is wanting to effect a modification of the excitement, only the 

 ordinary nerve-current is set in motion, which communicates the simplest sen- 

 sation, the common feeling, namely, of pain. The same is the result in the case 

 of pressure, which, producing at the cxt'rcmitics only a sensation of pressure, 

 occasions pain when applied to the stem. In making the experiment mentioned, 

 another noticeable distinction will occur to every attentive observer. On im- 

 mersing the fingers we perceive the cold in the portions of skin touched by the 

 cold water; with bandaged eyes we can exactly determine from the sensation 

 on which finger and what parts of the same the cold takes effect. In dipping 

 the elbow, however, till pain arises, we feel this pain, strangely enough, not at 

 the place which is immersed, but in the skin of the hand and finger ; in like 

 manner, these ar? the parts whiL-h pain us when we strike that portion of the 



