Observations on certain parts of the animal oeconomy / by John Hunter.

  • Hunter, John, 1728-1793.
Date:
MDCCXCII [1792]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on certain parts of the animal oeconomy / by John Hunter. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    ON THE COLOUR OF THE PIGMENTUM OF THE EYE IN DIFFERENT ANIMALS. IN the eyes of all animals which I have examined, there is a fubftance approaching to the nature and appearance of a membrane, called the pigmentum, which lines the choroid coat, and is fomewhat fimilar to the rete mucofum which lies under the cuticle of the human body; and there is alfo fome of the fame kind of fubftance diifufed through the cellular- membrane, which unites the choroid with the fclerotic coat. My inten- tion, at prefent, is only to communicate the obfervations I have made on this fubjeft, and its ufe, confining myfelf to the confideration of that kind of it which lines the tunica choroides of the clafs Mammalia, and of birds : in doing which I fhall alfo take occafion to fpeak of the difference of colour occurring in animals of the fame fpecies. Although an accu- rate examination of the appearances of a fimilar fubftance in the eyes of fome fifties might illuftrate the fubjedt, we cannot avail ourfelves of that, as from not being fufficiently acquainted with the eifefts of light on the eyes of that clafs of animals. The propagation, or continuance of animals in their diftindl clafles, is an eftabliftied law of Nature; and, in a general way, is preferved with a tolerable degree of uniformity : but in the individuals of each fpecies, va- rieties are every day produced in colour, ftiape, fize, and difpofition. Some of thefe changes are permanent with refpedt to the propagation of the animal; becoming fo far a part of its nature as to be continued in the offspring. Animals living in a free and natural ftate are fubjecft to few deviations from their fpecific charadler; but Nature is lefs uniform in its operations