LIFE AND MIND 



of organs of sense. One of the most notable 

 achievements of modern biology is the discov- 

 ery — due among others, to Huschke, Remak, 

 Milne - Edwards, and Huxley — that all the 

 sense-organs are but successive modifications of 

 tactile structures, or rather, of those simple der- 

 mal structures which in the higher organisms 

 are specialized as tactile. The most perfect or- 

 gans of touch are the vibriss^e or whiskers of the 

 cat, which act as long levers in communicating 

 impulses to the nerve fibres that terminate in 

 clusters about the dermal sacs in which they are 

 inserted. Yet these whiskers are merely spe- 

 cialized forms of just such hairs as those which 

 cover the bodies of most mammals, and which 

 are found evanescent upon the human skin, em- 

 bedded in minute sacs or reentrant folds. Now 

 it is a demonstrated fact that the eye and ear 

 are morphologically identical with vibrissa. The 

 bulb of the eye and the auditory chamber are 

 nothing but extremely metamorphosed hair- 

 sacs, and the same is true of the olfactory cham- 

 ber. The crystalline lens is a differentiated hair, 

 the aqueous and vitreous humours are liquefied 

 dermal tissue, and the otolites of the ear are 

 " concretions from the contents of an epider- 

 mic sac." In view of these astounding disclo- 

 sures of embryology, we may readily assent to 

 Mr. Spencer's statement that modern science 

 justifies the guess of Demokritos, " that all the 

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