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XXVIII. Observations on the Spectra of the Eye and the Seat 

 of Vision. By Mrs. Griffiths.* 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 

 HP HE main object which induced me to communicate the 



■*■ curious discovery of the vision of the retina, was to elicit 

 the attention of the English philosophers to that part of it 

 which related to the seat of vision. This question has been 

 lost sight of entirely; and although I have been gratified with 

 the zeal with which Sir David Brewster has pursued the ex- 

 periment, yet it has taken a different course from the one I so 

 much desired. 



In the remarks on my communication, the Editor observes 

 that " some of the conclusions in the paper, especially those 

 about the seat of vision, are not correct." It is not specified 

 in what the error consists. I assert on good grounds that the 

 office of the retina is to contract and dilate the pupil. When 

 the pupil contracts, the intersections or meshes of the retina 

 are elongated, and of course they are thinner, and the inter- 

 stices or squares between are larger. When the pupil dilates, 

 the lines, or meshes, or intersections, whatever they may be 

 called, are thicker, and the spaces between are smaller. 

 Surely this proves that the retina is of an elastic nature, and 

 its office is sufficiently well denned. ^ 



Is it philosophical to suppose that a part of the eye so sin- 

 gularly constructed can transmit the impressions of external 

 objects to the sensory ? It is composed of squares, with re- 

 gular intervals of interstices, and these squares are for ever 

 varying with every change of light ; in which way, there- 

 fore, could this separate apparatus transmit all the various 

 forms which are presented by external objects ? Perhaps there 

 is no portion of the eye so little adapted to the purpose of 

 transmitting objects or impressions as the retina, and I would 

 enlarge on this point did I not think that some abler pen 

 would soon appear to discuss the matter in a fuller form. I 

 wish the fact to be established, that the seat of vision does not 

 belong to any one part of the eye in particular, but that the 

 whole apparatus of the eye is necessary to the conveyance of 

 external impressions to the sensory. 



I consider the eye, as it respects mental vision, as an ex- 

 ternal object, and that under different modifications of light 

 every portion of it can be seen. For instance,Mr.W.G. Horner 

 can see the " blood-vessels of the retina." I can see the retina, 

 the opening of the pupil, the crystalline lens, the air-bubbles 



• See Lond. and Edinb. Phil. Mag. vol. iv. pp. 43, 115, 241,262, and 

 354.— Edit. 



