852 A MANUAL OF PHYSIOLOGY 



way withdrawn from or imparted to the cutaneous tissues 

 with sufficient abruptness, a sensation of cold or heat is 

 experienced. And when two portions of the skin at different 

 temperatures are put in contact, we feel that, relatively to 

 one another, one is warm and the other cold. But it is 

 worthy of remark that it is only difference of temperature, 

 and not absolute height, that we are able to estimate by 

 our sensations. Thus, a hand which has been working in 

 ice-cold water will feel water at 10 as warm ; whereas it 

 would appear cold to a warm hand. When the temperature 

 of the skin is raised above or diminished below a certain 

 limit, the sensation of change of temperature gives place to 

 one of pain ; and this may be considered as due either to 

 excessive stimulation of the end-organs of the temperature 

 sense, or as due to stimulation of the ordinary sensory 

 nerves, which are normally insensible to more moderate 

 variations of temperature. 



The recent researches of Blix, Goldscheider, and others 

 have thrown new light upon the anatomical basis of the 

 sensations which have their origin in the skin. They have 

 found that the whole skin is not endowed with the capacity 

 of distinguishing temperature. The temperature sense is 

 confined to minute areas scattered over the cutaneous 

 surface, some of which are * cold ' points, i.e., respond to 

 variations of temperature only by a sensation of cold, while 

 others are ' warm ' points and respond only by a sensation 

 of heat. ' Cold ' points are present in greater number than 

 'warm.' When a nerve is compressed, the sensibility of 

 the tract supplied by it disappears for cold sooner than for 

 heat. 



The explanation of these facts seems to be that the skin is supplied 

 with several kinds of nerve-fibres, anatomically as well as functionally 

 distinct. Some fibres minister to the sensation of cold, others to 

 that of heat, others to that of pressure, others, perhaps, to that of 

 contact, and others still to pain. And just as stimulation of the 

 optic nerve gives rise to a sensation of light, so stimulation of any 

 one of the cutaneous nerves gives rise to the specific sensation proper 

 to the group to which it belongs. But with the eyes closed a thermal 

 may sometimes be mistaken for a tactile stimulus. 



It is not only of physiological interest, but of practical importance, 



