GENERAL SENSATIONS. 545 



and the eyelids are especially sensitive to changes of temperature, 

 a fact known by people who want a ready gauge of the heat of a 

 body thus, a barber approaches the curling-tongs to his cheek 

 to measure its temperature before applying it to the hair of his 

 client. The middle of the chest, moreover, is very sensitive to 

 heat, while it is dull in feeling tactile impressions. 



The hand is far from being the best gauge of temperature, for 

 heat appreciation is not developed in a due proportion to the 

 keenness of the tactile sensibility. The larger the surface ex- 

 posed to changes of temperature the more accurate the judgment 

 at which we can arrive the slightest changes being at once rec- 

 ognized when the entire surface of the body is exposed to them. 

 The foregoing facts are well known to persons in the habit of 

 testing the temperature of a warm bath without the aid of a 

 thermometer ; they do not use the limited surface of a sensitive 

 tactile finger-tip, but plunge the entire arm into the water. The 

 elbow, indeed, is the common test used by nurses in ascertaining 

 that the water in which they are about to wash an infant is not 

 too warm for that purpose. 



Great extremes of heat or cold, such, in fact, as would act as 

 stimuli to a nerve fibre, do not give rise to sensations of different 

 temperatures, but simply excite feelings of pain. Thus, if one 

 plunges one's hand into a freezing mixture or into extremely hot 

 water, it is difficult to say at once whether they are hot or cold 

 in both cases pain being the only sensation produced. 



GENERAL SENSATIONS. 



We call general sensations those feelings, pleasurable or other- 

 wise, which can be excited in us, without our being able to refer 

 them to external objects, or compare their sensation with those of 

 the special senses, or even to describe their exact mode of percep- 

 tion. Under this head are enumerated Pain, Hunger, Thirst, 

 Nausea, Giddiness, Shivering, Titillation, Fatigue, etc. 



Of these only pain is commonly referred to any given part, 

 and the attempt to localize pain with exactness soon shows how 

 very different is our power in this respect in the case of pain and 

 in the case of tactile impressions. Thus, when we strike our 



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