The seat of vision determined : and, by the discovery of a new function in the organ, a foundation laid for explaining its mechanism and the various phenomena, on principles hitherto unattempted / by Andrew Horn.

Horn, Andrew

Date:: 1813

Credit: The seat of vision determined : and, by the discovery of a new function in the organ, a foundation laid for explaining its mechanism and the various phenomena, on principles hitherto unattempted / by Andrew Horn. Source: Wellcome Collection.

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

41/118 page 35

$M. Pecquet and others, that the retina, and not the choroides, ought, for various reasons, to be regarded as the proper or- gan that receives the impressions of the rays of light, and communicates them by the optic nerve to the common sensory. Mariotte, in support of his hypothe- sis, considered the transparency of the retina, a strong argument against the function usually assigned it. He observ- ed that like air, or water, or the crystal- line and other humours, it can receive little or no impression from the rays of light; like them, it must transmit the rays to another substance better qualified to re- ceive and stop their impressions. He therefore concluded, that the opacity of the choroides, pervaded by the pigmentum nigrum, evidently points out its office, and shews that it is designed, by nature, to be the principal organ of vision. ' w • * I. * •. ' * I r . Jj\ t * J' He was further confirmed in his opinion of the small degree of sensibility in the d 2$