42 



seating a mode of sensation without any special organ, 

 and described as a vital or internal sense diffused over the 

 whole body, by means of which we are sensible of what 

 takes place within us, is now generally recognised. Sen- 

 sation is said to consist in the mind receiving, through the 

 medium of the nervous system, and, usually, as the result 

 of the action of an external cause, a knowledge of certain 

 qualities or conditions, not of external bodies, but of the 

 nerves of sense themselves, and these qualities of the nerves 

 of sense are in all different, the nerve of each sense having 

 its own peculiar quality. Smell, sight, and hearing depend 

 for their manifestation on the existence of a special nerve 

 for each ; whereas taste appears to be a property common 

 to branches of two nerves, and touch is not confined 

 to particular parts of the body, of small extent, like the 

 other senses ; on the contrary, all parts capable of per- 

 ceiving the presence of the stimulus by ordinary sensation 

 are, in certain degrees, the seat of this sense; for touch 

 is simply a modification or exaltation of common sensation 

 or sensibility. The nerves on which the sense of touch 

 depends are, therefore, the same as those which confer 

 ordinary sensation on the different parts of the body. 1 



Touch may be regarded as the universal, fundamental 

 sense possessed by all sentient animals, as Mr. Herbert 

 Spencer 'has ably demonstrated how the other senses, by 

 evolution and specialization, could have arisen from the 

 sense of touch. Tactile sensations, and the sensations of 

 temperature, are alike subject to heredity. Prosper Lucas 

 says that " parents transmit to their children the most 

 singular perfections and imperfections of touch. There 

 are, probably, in the skin, no modes of hyperaesthesia, or 

 1 Kirkes' Physiology. 



