PHYSIOLOGICAL PARADOXES. 



arrangements being made, and who is blind- 

 folded to prevent him from seeing vapour from 

 the warmer water, hold his hands for a minute 

 one in the water in A and the other in that in 

 B, and then say which is the warmer. He will, 

 of course, say that A is decidedly warmer than 

 B. Let him then take his hands out of A and 

 B, and put them immediately into C and D, 

 which are both of the same temperature, and 

 say at once which is the warmer. He will 

 be sure to say that D is, unless he knows the 



A B C D 



FlQ. 58 THE NERVES AND IMPERFECT SENSE OF TEMPERATURE. 



trick from previous experience, and wishes to 

 have the amusement of spoiling the trial. 



The reason of his mistake is very plain. 

 The hand which went into C had previously 

 been in very warm water, so that C felt much 

 colder. The hand in D had previously been 

 in cold water, so that D felt much warmer. The 

 sensation of relative temperature or change of 

 temperature is much finer than that of actual 

 temperature, so that while the right hand feels 

 a clear sensation of being warmed, and the left 

 of being cooled, the judgment inevitably decides 

 that the agent which is producing the former 

 effect is itself warmer than the other. 



The paradox can be pushed a little further 

 260 



