SENSE OP TOUCH. 165 



shivering with cold, and both sensations are produced by the 

 same temperature. Frozen mercury excites the same sensa- 

 tion as red hot iron. A piece of marble will feel colder than 

 a woollen garment, although both be of the same temperature, 

 because the marble is a better conductor of heat than wool- 

 len ; a deep cellar appears warm to us in winter, and cold in 

 summer, though its temperature is nearly the same all the 

 year round. During the voyages made by Captain Parry 

 to discover the north-west passage, it was found that after 

 having lived for some days in a temperature of 15 or 20 de- 

 grees below zero, it felt quite mild and comfortable when the 

 thermometer rose to zero and conversely. The sense, there- 

 fore, only gives us an idea of the relative, not the actual 

 heat of bodies/ 



22. (The sense of feeling may become blunted to, an extra- 

 ordinary degree) \Chabert, the Fire King, was said to have 

 been in the habit of swallowing forty grains of phosphorus 

 at once ; washing his hands in melted lead ; and drinking 

 boiling oil, without any apparent injury. There is a great 

 difference in the degree of sensibility of the mucous mem- 

 brane, in different individuals, some being able without in- 

 convenience, to swallow fluids of a temperature which 

 would be very uncomfortable to others/ 



23. The tactile power of the skin is not proportionate to 

 its sensibility. Thus the arm-pits, flanks, soies of the feet, 

 and other parts of the body, have slight power of distinguish- 

 ing objects by touch, although they are very sensible. It 

 would be difficult to make a person laugh by tickling the 

 ends of his fingers, and yet we have seen that their sense of 

 touch is more delicate than that of any other portion of the 

 skin. All the surfaces and solids of the body possess a kind 

 of sensibility, peculiar to themselves, and in disease may give 

 sensations, but this a different property from that of touch. 



Questions. What is a sensation ? How are they divided? What 



