THE SENSES. 167 



by a thermometer. All that we can with safety infer from our sensations 

 of temperature, is that a given object is warmer or cooler than the skin. 

 Thus the temperature of our skin is the standard; and as this varies from 

 hour to hour according to the activity of the cutaneous circulation, our 

 estimate of the absolute temperature of any body must necessarily vary 

 too. If we put the left hand into water at 40 F. and the right into water 

 at 110 F. and then immerse both in water at 80 F., it will feel warm to 

 the left hand but cool to the right. Again, a piece of metal which has 

 really the same temperature as a given piece of wood will feel much 

 colder, since it conducts away the heat much more rapidly. For the 

 same reason air in motion feels very much cooler than air of the same 

 temperature at rest. 



Perhaps the most striking example of the fallaciousness of our sensa- 

 tions as a measure of temperature is afforded by fever. In a shivering fit 

 of ague the patient feels excessively cold, whereas his actual temperature 

 is several degrees above the normal, while in the sweating stage which 

 succeeds it he feels very warm, whereas really his temperature has fallen 

 several degrees. In the former case the cutaneous circulation is much 

 diminished, in the latter much increased; hence the sensations of cold and 

 heat respectively. 



In some cases we are able to form a fairly accurate estimate of absolute 

 temperature. Thus, by plunging the elbow into a bath, a practised bath- 

 attendant can tell the temperature sometimes within 1 F. 



The temperatures which can be readily discriminated are between 

 50 115 F. (10 45 C.); very low and very high temperature alike 

 produce a burning sensation. A temperature appears higher according 

 to the extent of cutaneous surface exposed to it. Thus, water of a tem- 

 perature which can be readily borne by the hand, is quite intolerable if 

 the whole body be immersed. So, too, water appears much hotter to the 

 hand than to a single finger. 



The delicacy of the sense of temperature coincides in the main with 

 that of touch, and appears to depend largely on the thickness of the skin; 

 hence, in the elbow where the skin is thin, the sense of temperature is 

 delicate, though that of touch is not remarkably so. Weber has further 

 ascertained the following facts: two compass points so near together on 

 the skin that they produce but a single impression, at once give rise to 

 two sensations, when one is hotter than the other. Moreover, of two 

 bodies of equal weight, that which is the colder feels heavier than the 

 other. 



As every sensation is attended with an idea, and leaves behind it an 

 idea in the mind which can be reproduced at will, we are enabled to com- 

 pare the idea of a past sensation with another sensation really present. 

 Thus we can compare the weight of one body with another which we had 

 previously felt, of which the idea is retained in our mind. Weber was 



