SENSE OF TOUCH. 861 



perceived. There was, it is true, a slight sensation of cold in the gastric region ; 

 but, as it only occupied the situation of the anterior wall of the stomach, it was 

 attributable to the abstraction of heat from the abdominal integuments in con- 

 tact with this. In an opposite experiment, the author drank quickly three 

 glasses of milk, the temperature of the first of which was 158, that of the second 

 145, whilst that of the third was intermediate between the two. The sensation 

 of heat could not be traced lower down than that of the cold in the previous ex- 

 periment. At the moment when the fluid entered the stomach, there was a 

 feeling which remained for some time, but which could not be distinguished as 

 heat, being mistakable for cold. In order to ascertain the sensation produced 

 in the large intestine by cold water, an injection of 14 ounces of water of the 

 temperature of 65 was thrown up the rectum } but scarcely any sensation of 

 cold could be perceived from it. In another instance, 21 ounces of water at 

 the same temperature were thrown up, without any resulting sensation of cold. 

 In both these cases, on the return of the enema a few minutes afterwards, a 

 distinct feeling of cold was experienced at the anus. When water of so 

 low a temperature as 45 J was injected, the first feeling excited was a 

 sensation of cold in the immediate neighborhood of the anus, and then a feeble 

 movement in the bowels; but a little time afterwards, there was a faint sensation 

 of cold, especially in the anterior wall of the abdomen. This sensation, how- 

 ever, remained after the return of the water ; and may hence be attributed to 

 the abstraction of warmth from the abdominal integuments, which was proved 

 to take place, the temperature of the surface being lowered 3. So, again, if 

 the cavity of the nose be filled with cold water, the coldness is only perceived 

 in the parts of the cavity which are most endowed with the proper tactile sense, 

 namely, the neighborhood of the nostrils and of the pharynx ; and it is not all 

 discernible in the higher part of the cavity, which is especially subservient to 

 the olfactory sense. But when the water injected is very cold (e. g. 41), a 

 peculiar pain is felt in the upper part of the nasal fossse, extending to the re- 

 gions of the forehead and the lachrymal canals ; this pain, however, is altogether 

 different from the sense of coldness. From the foregoing experiments, it ap- 

 pears fair to conclude that the sensory nerves have no power of receiving im- 

 pressions indicative of difference of temperature, unless those impressions are 

 communicated through a special organ ; but they afford no adequate ground for 

 the supposition that a set of nerve-fibres is provided for their transmission, dis- 

 tinct from those which minister to common sensation. This conclusion is confirmed 

 by the fact that we cannot excite impressions of heat or cold by direct applica- 

 tion to the trunks of nerves which we know must conduct such impressions ; for 

 the parts of the skin, immediately beneath which lie large nerve-trunks, are 

 not more sensitive to moderate heat or cold than are any others ; whilst a greater 

 degree of either is felt as pain, not as a change of temperature. Thus, a 

 mixture of ice and water, applied over the ulnar nerve, affects it in fifteen 

 seconds, and produces severe pain, having no resemblance to cold, such as cannot 

 be excited by the same cold applied to any other region. So the nerve of the 

 tooth-pulp is equally and similarly affected by water of 43 and of 112 ; either 

 application causing a pain exactly similar to that excited by the other, or to 

 that produced by pressure. The same is true of the impressions received through 

 the skin itself, when they pass beyond certain limits of intensity ; thus, the 

 sensation produced by touching frozen mercury is said to be not distinguishable 

 from that which results from touching a red-hot iron. 



867. The improvement in the sense of Touch, in those persons whose depend- 

 ence upon it is increased by the loss of other senses, is well known ; this is 

 doubtless to be in part attributed (as already remarked) to the increased 

 attention which is given to the sensations, and in part, it may be surmised, to 

 an increased development of the tactile organs themselves, resulting from the 



