"COLD" AND " WARMTH 1 ' SENSATIONS. 



955 



efficient ; for the nipple, 40° C. suffices. Alrutz 1 found 48° C. for the 

 elbow, and 52" C. for the forehead, sufficient. According to Alrutz, the para- 

 doxical cold sensation can also be evoked in the following ways: — (1) By 

 applying to the inner side of the elbow, or to the front of the thigh, a 

 silver plate (Thunberg's) 2 of 4 c.c. surface and 25 /x. thick, heated to 100° C. 

 A short cold sensation is immediately felt, succeeded by a "hot" sensation, and 

 sometimes by a painful one. With thicker plates the final sensation of pain 

 is of regular occurrence. (2) By fatiguing the warmth spots. A piece of 

 metal at 52° to 54° C. is laid on the front of the forearm. It evokes a hot 

 sensation, then this declines, and a cold sensation is felt pricking through. 

 (3) After a bath of water at 37° to 39° of some duration, the foot is passed 

 quickly through very hot water. The first feeling that then ensues is of 

 " cold so distinct and so pure as to be indistinguishable from cold water " ; 3 

 this subsides, and after it is felt a smarting painful sensation. Cold stimuli, 

 even severe, are not found by Alrutz to give " warmth " or "heat" sensations. 



Some characters of "cold "and "warmth" sensations. — Contact 

 under feeble pressure with an object of the "adequate temperature" elicits 

 from neither a " cold spot " nor a " warmth spot " any tactual sensation. 

 But if the contact, although feeble, be with an object sufficiently cool or 

 hot, it will elicit a corresponding thermal sensation (Goldscheider), which 

 may be combined with sensations which are in part at least tactual. 

 At many, though not at all, thermal " spots," it can also be shown that 

 analgesia exists, at least so far as to tests by pricking with a needle. 

 When tested by a highly-heated metal point, able to elicit almost 

 unbearable smarting, a thermal spot evinces little, or much less, pain, 

 although if the " spot " be a " warmth spot," a hot feeling arises. 

 Goldscheider considers the sensation ordinarily evoked by contact with 

 an object hot enough to be " painful," to be compound of (1) warm 

 sensations of high intensity, due to strong adequate stimulation of 

 " warmth spots " ; (2) tactual sensations evoked by contact in accordance 

 with conditions laid down in the previous chapter ; (3) pain sensations 

 evoked by the physical heat exciting pain-nerves and their endings, in 

 virtue of its property as a general nerve stimulus. 4 The " burning," 

 painful sensation of a hot body, on this view, owes its painful quality, 

 not to over-excitation of " warmth spots," but to concomitant excitation 

 of pain-nerves by the heat. 



When the temperature of the cuticle rises to 48°-49° C, or falls 

 to 12°-11° C, pain, in addition to thermal sensation, results. 5 The 

 above are average figures. The extreme temperatures at which stimuli, 

 when applied to the skin, still evoke purely, i.e. not painful, thermal 

 sensations (if one may for brevity use thermal in that meaning), varies 

 under various conditions — (1) It is different in different skin regions; 

 (2) it depends greatly on the duration of application of the stimulus. 

 The hand dipped into water at 50° C. feels for the first moment a pure 

 " warmth " sensation, without any painful character. The sensation then 

 decreases somewhat, and then increases, rapidly becoming painful. A 

 silver plate of about 4 c.c. surface can be laid on the skin at a tempera- 

 ture of above 110° C, and allowed to cool there, without causing pain, if 

 it be only -01 mm. thick : if it be - 5 mm. thick, it will evoke pain and 



1 Skandin. Arch. f. Physiol., Leipzig, 1897, Bd. vii. ; also Kiesow, op. cit. 

 "Skandin. Arch. f. Physiol., Leipzig, 1897, Bd. vii. 



3 Mind, London and P]dinb., 1898, vol. vii. p. 141. 



4 Goldscheider, loc. cit. 5 Weber, loc. cit. 



G For details, see Donath, '■ Ueber d. Grenze, etc.," Arch. f. Physiol., Leipzig, 1884, S. 694. 





