STUDENT LIFE AND EARLY MANHOOD 



world after the publication of his great text-book of 

 physiology. Here were found not only all the facts 

 of the science then known, but also the discussion 

 of principles. In particular, the physiology of 

 nerves, of nerve centres, and of the senses, was ex- 

 pounded in a manner that hitherto had not been 

 attempted. Miiller also laid the foundations of the 

 school of modern experimental psychology by placing 

 on a clear basis the mode of action of external 

 stimuli on the terminal organs of sense. He showed 

 that in whatever way a terminal organ is stimulated, 

 the result is the same in consciousness, according to 

 the nature of the particular terminal organ. Thus 

 if we stimulate the retina of the eye by light, or 

 electricity, or heat, or mechanical pressure, as by a 

 blow, the result will always be the same namely, 

 the sensation of a flash of light, possibly of colour. 

 Further, the same result follows any kind of irritation 

 of the optic nerve, which conveys the impulses from 

 the retina to the brain ; and from this he deduced the 

 great law of the specific sensibility of nerves, by 

 which he meant that each nerve of special sense has, 

 as it were, its own sensibility, so that, in whatever 

 way it may be stimulated, the result will always be 

 the same. This doctrine was especially fruitful in 

 the hands of Helmholtz, Fechner, Brucke, Hering, 

 and many others. It was a great step to recognise 

 that the ' sensation due to a particular nerve may 

 vary in intensity, but not in quality, and therefore 



