"COLD" AND "WARMTH" SENSATIONS. 957 



and in the same area of skin, at different times. Its value is determined 

 by "adaptation." When an area of normal skin is resting at such a 

 thermal equilibrium, i.e. is generating in its own sense organs of cold 

 and warmth no trace of sensation detectable by us, that skin has its 

 thermal sense organs in a state of " complete adaptation " to the thermal 

 conditions of the moment. In a comfortable room we feel at no part of 

 the body either hot or cold, although different parts of the surface are 

 at different temperatures, with almost 10° C. between them, e.g. lobe 

 of ear 28 0, 8 C, tongue 37°"6 C. When we pass from such a room to 

 another which is colder, we experience at first a feeling of cold. 

 But this feeling after a time, if the room be not too cold, passes off. 

 Hering says that under such conditions the temperature of the skin, 

 physically measured, is somewhat lower in the second room. But the 

 thermal sense organs within a certain range adjust themselves to the 

 altered conditions, and a fresh physical temperature is taken for the 

 physiological zero. On then returning to the former room, we experi- 

 ence a sensation of warmth ; and this persists in decreasing degree 

 until the physiological zero temperature has been re-established at the 

 original skin temperature — as measured by the thermometer — once 

 more. This adaptation there is no doubt is much greater in range 

 and speed in some individuals than in others. 



The range of physical temperature through which the subjective 

 zero temperature may oscillate in virtue of "adaptation," can also be 

 illustrated by experiments such as those given above on p. 953, in which 

 a portion of body surface is brought into contact with objects of various 

 temperature and thermal quality. But it plays a more important part 

 in the formation of certain perceptions than of others. The sensa- 

 tions of cold and warmth evoked from the cutaneous organs are in 

 respect to projection like those of touch, intermediate in kind between 

 visual and muscular. In respect to projection, it is easy to distinguish 

 two groups of thermal sensations, the one group much more pro- 

 jected than the other. Many of our thermal sensations are habitually 

 concomitant with tactual, e.g., we touch a warm object to feel if it 

 is hot, etc. 



It has been shown that a cold spot does not evoke a sensation of " touch," 

 if contact of a test-object with it be sufficiently feeble. It does not, however, 

 appear to have yet been shown that by contact more intense no sensation 

 akin to touch is producible at a thermal spot. The glans penis and the cornea, 

 endowed practically only with pain spots and cold spots, yet yield sensations 

 in response to contact which possess some, though perhaps remote, likeness to 

 touch ; and these sensations, evoked from these parts by thermal stimuli 

 acting in contact with them, are different from those evoked by thermal 

 stimuli applied without contact, and the difference appears to me one of 

 quality. These sensations in which the tactual and the thermal senses com- 

 bine are to some extent projected ; and to such an extent, even where the 

 pure tactual component must be slight, e.g. in examining fluids (see above, 

 p. 924), as to suggest that the thermal end-organs themselves display some 

 reaction to tactile objects. The warmth perception resulting from contact with 

 a hot body is referred to the hotness of the hot body ; the expressions 

 "burning hot" "scalding hot," " comfortably warm," etc., are applied not to 

 any part of " me," but partly to the skin and partly to the heated object. It is 

 noteworthy that in the great majority of instances the thermal sensations 

 accompanied by sensible contact are obtained actively, that is to say, by 

 muscular movements which bring the sensifacient surface into contact with the 



