454 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



37 



29 



] I I ii i ii r r ilif(»i)*iiM>Wiil>liii | i M iiill« » iil»ii M iilil> MN II'lll< l l 



sf 



vc B 



29'- 



■^^— *— * I ii>ii I iiimiiiiiiiiiii I mill 



('Weber's deception'Ji. The pressure sensation caused 

 by cooling the skin has been the subject of thorough 

 examination by later workers. Kiesow (62) con- 

 firmed the existence of 'Weber's deception' and also 

 succeeded in provoking sensations of pressure by 

 application of ether and chloroform to the skin, and 

 Goldscheider & Hahn (33), experimenting with vari- 

 ous solutions and with cooled air, came to the conclu- 

 sion that the mcchanorcccptors could be stimulated 

 by cooling. 



FIG. 23. .Simultaneous records of cold impulses from receptor 

 field on upper surface of cat tongue and of temperature of both 

 surfaces. A, on cooling of the upper surface; B, on cooling of 

 the lower surface; a, temperature of the upper surface; b, tem- 

 perature of lower surface. Time marks, 1 5 cps. [From Hensel & 

 Zotterman (55)-] 



of the cold receptors does not depend upon the direc- 

 tion or slope of intracutaneous temperature gradient. 

 Thus temperature gradients between blood vessels 

 and the receptors, which were suggested as the ade- 

 quate stimulus, cannot be decisive since arrest of the 

 circulation for a minute or so did not notably change 

 the results obtained by the retrograde temperature 

 gradient. 



RESPONSE OF MECH.iiNORECEPTORS TO THERM.'^L STIMU- 

 LATION. When the tongue of the cat or dog is cooled, 

 it is generally possible only to record small cold spikes 

 in the lingual nerve, whereas the large touch and pres- 

 sure spikes cannot be elicited by cooling. However, in 

 a few cases cooling also sets up relatively large spikes 

 in the lingual nerve. Hensel & Zotterman (53) investi- 

 gated this phenomenon further and demonstrated that 

 these larger spikes derived from mechanoceptive 

 nerve fibers. These large spikes usually appear only 

 with severe cooling and disappear within a few seconds 

 at a constant low temperature, whereas small cold 

 spikes appear with slight cooling and persist at con- 

 stant temperatures for long periods (fig. 24). It was 

 shown that this activity of mechanoceptive fibers 

 could not ije due to secondary mechanical stimulation 

 of the pressure receptors by local vasoconstriction nor 

 to stimulation of the nerve trunk by cooling. It is only 

 medium-sized mechanoceptive fibers (8 to 10 /li) 

 which were stimulated by cooling the surface; the 

 larger pressure fibers (12 to 15 m) were not excited. 



These findings offer a ready explanation for the 

 well-known phenomenon first described by Weber (94) 

 that cold weights seem heavier than warm ones 



Injiiience of Nonthermal Agencies 



That menthol evokes cold .sensations when applied 

 on the tongue as well as on the skin is a well-known 

 experience which has been exploited in manifold ways. 

 It has likewise long been known that these cold sensa- 

 tions are not caused by physical cooling of the skin or 

 the mucous membranes but by some chemical action 

 directly on the cold receptors (32). Hensel & Zotter- 

 man (56) recorded the discharge of cold fibers after 

 the application of menthol solutions upon the tongue 

 using well defined thermal stimulation. 



^ *0r', 



tiipiiiiiiii iiniiiiiiiiiiiijutiiiiiiiiiyyiimy 



""""""""""" '""" ■'■■ """ ■"""■" """■ 



■tOOuV 



..MJJJ.I.L:; 



III., 1 



t i i M liiiiii m i H ifc 



C^X'C 



50 



JHlMtwaAid&iii«^4«t«ittjate 



MMlwilllikMiiLd^^ 



£*0 



50 



tmtt^u^mttmJm^iikiii^ditmdtiMithit 



FIG. 24. Records from a thin strand of the cat lingual nerve 

 obtained on applying mechanical and thermal stimuli to the 

 tongue. The Ihin line shows the temperature of the surface of the 

 tongue. A, pressure; B, cooling from 41° to 22°C; C, cooling 

 from 41 ° to 26°C; D, cooling from 41 ° to 2()°C; E, cooling from 

 41° to 32 °C. Time marks, 50 cps. [From Hensel & Zotterman 

 (53)-] 



