The five senses of man.

  • Bernstein, Julius.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: The five senses of man. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    eye may have all the appearance of a sound one, it may receive the rays of light and form an image of objects on its background, and nevertheless no sensation can be produced, for the connection with the brain, the centre of the nervous system, is wanting. The case is the same with the deaf ear, and with the arm devoid of feeling. The sensory organs are, therefore, only instruments of the mind, which has its seat in the brain, and by means of nerves makes use of these instruments to obtain information of external objects. The forces which operate in the outer world—namely, light, heat, sound, motion, and chemical affinity—produce in the sensory organs an irritation of the sensory nerves connected with them, and these convey the irritation which is there received throughout their entire length to the brain. Each organ of sense has its own specific irritation by which it is excited. The terminations of the optic nerve in the eye can only be excited by light-waves, not by sound-waves, and the latter can only excite the terminations of the auditory nerve in the ear. For the tactile nerves of the skin mechanical pressure and heat are specific excitements ; for the nerves of taste and smell some chemical substance is necessary. The sensation itself evidently first takes place in the brain. The sensation of light does not take place in the eye, where there is only an impression of light upon the expanded surface of the optic nerve ; the sensation of light cannot, however, take place in the optic nerve itself, for it merely conveys the fact of the existence of the irritation to the brain. The sensation of light, a process to us most obscure, begins rather in the brain, which is