Illustrations of instinct deduced from the habits of British animals / By Jonathan Couch.

  • Jonathan Couch
Date:
1847
Catalogue details

Licence: Public Domain Mark

Credit: Illustrations of instinct deduced from the habits of British animals / By Jonathan Couch. Source: Wellcome Collection.

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    sensibility of these organs becomes deranged by what must be considered a morbid action, the nature of the perception is altered; and the impression of what we must call the true taste, sight, or smell is converted into another which is offensive and unnatural. The optic nerve, under deranged or excessive excitement, sees every object in a changed or aggravated condition*: the flame of a candle is obscured, or is seen as a blaze; a sparkle appears like a fire; and the painful sense of vision continues even after the eyes are closed. The senses of taste and smell are still more easily and frequently deranged: a vitiation of the sense of taste, or its suspension, is in some persons permanent; and the former may be commonly traced to a change in the nature of the secretion of saliva: for this taste is often most perceptible when nothing extraneous has been received into the mouth. At other times it is due to a false perception in the nerve of that organ, when, even if a naturally agreeable object be presented to it, a disgusting sensation is experienced ; which feeling of disgust will be continued by sympathy of remem- brance, long after the condition that produced it has ceased: a circumstance that will account for * That condition of visual perception, which is termed Daltonism, is best explained on the principles here advanced: for as the only natural stimulus to the optic nerve is light, it is easy to understand how the fibres of the optic nerve may be in such a state, that a peculiarly-coloured ray may produce no impression, or only an imperfect one. The nerve may be incapable of receiving any other than a morbid or modified impulse, and the sensation communicated must be of a corresponding nature.
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