that substance. If, for example, the hands be great- 

 iy cooled, and then plunged into fresh pump-wa- 

 ter, the water will communicate the sensation of 

 heat, while the same water, at another time, when 

 the hands were previously warmed, would impress 

 the sensation of cold. In like manner, we are often 

 not conscious of any feeling of cold in our hands or 

 feet, but if we apply them to a less exposed and 

 warmer part of the body, the feeling of cold is im- 

 pressed on that part. The same fallacy with regard 

 to the actual temperature of the body, as indicated 

 by our sensations, exists, when those sensations are 

 connected with internal causes ; for a general feel- 

 ing of cold not unfrequently extends over the body, 

 where no variation in its actual temperature, or in 

 that of the surrounding bodies, has occurred. " In 

 the beginning of an ague fit, when I was all shiver- 

 ing and under a great sense of cold," says Dr Mar- 

 tine, " my skin was two or three degrees warmer 

 than in a natural healthy state V 



186. But the actual temperature of the human 

 body, is not only in a great degree independent of 

 sensation, but also of the variations in temperature 

 which the surrounding medium suffers. Governor 

 Ellis, in the year 1758, observed, that a person re- 

 maining in a medium higher in temperature than 

 that of his own body, preserved, nevertheless, his 

 natural standard heat. Dr Fordyce went successive- 

 ly into three rooms heated to 90, 11Q, and 120. 

 He staid in the first room five minutes, which gently 



* Qn Thermometers* p. 150. 



P3 



