ABSTRACT
The excitation of a peripheral sensory apparatus, a tactile corpuscle for example, provokes a particular sensation, and no other stimulus, even that of an analogous corpuscle differently situated, will give the same sensation. Similarly, the appearance of a light whose image is thrown on a particular point of the retina will give a particular sensation, while an analogous excitation of any other part of the body will either give no sensation at all or one that is analogous but not identical—as in the case of the excitation of another retinal area.
