STRUCTURE OF SENSIFEROUS ORGANS 315 



have anything to do with that epidermis of which 

 gustatory and tactile and, at any rate, the lower 

 forms of auditory and visual, organs are obvious 

 modifications. 



Whatever he the apparent diversities among 

 the sensiferous apparatuses, however, they share 

 certain common characters. Each consists of a 

 receptive, a transmissive, and a sensificatory 

 portion. The essential part of the first is an 

 epithelium, of the second, nerve fibres, of the 

 third, a part of the brain; the sensation is always 

 the consequence of the mode of motion excited in 

 the receptive, and sent along the transmissive, to 

 the sensificatory part of the sensiferous apparatus. 

 And, in all the senses, there is no likeness what- 

 ever between the object of sense, which is matter 

 in motion, and the sensation, which is an im- 

 material phenomenon. 



On the hypothesis which appears to me to be 

 the most convenient, sensation is a product of the 

 sensiferous apparatus caused by certain modes of 

 motion which are set up in it by impulses from 

 without. The sensiferous apparatuses are, as it 

 were, factories, all of which at the one end receive 

 raw materials of a similar kind namely, modes of 

 motion while, at the other, each turns out a 

 special product, the feeling which constitutes the 

 kind of sensation characteristic of it. 



Or, to make use of a closer comparison, each 



