Mrs. Griffiths on the Spectra of the Eye and Seat of Vision. 193 



in the aqueous chamber; the aqueous humour itself flowing in 

 and circulating incessantly; the fixed spots on the outer sur- 

 face of the crystalline lens ; and the connected floating links 

 of air-bubbles, which, when numerous, cause the disease in the 

 eye called amaurosis # . 



The whole apparatus of the eye is therefore, to the mina\ 

 of no more importance than the internal machinery of a watch 

 is to the hour-hand of the dial-plate. The machinery of the 

 watch and of the eye is in constant motion, but no one part of 

 either is the direct cause of the movement of the hour-hand, 

 or of the perception of impressions. 



The mind sees the time as specified by the motion of the 

 hands, and the mind has the perception of impressions as spe- 

 cified by the simultaneous operations of the different portions 

 of the eyeball. By inspection, all the machinery of the watch 

 is visible to the mind, and by inspection, all the machinery of 

 the eye is visible to the mind likewise. 



The impression of external objects is instantaneous, and is 

 not transmitted from the object to any one particular part, 

 and thence to the sensory. Vision is impaired when any one 

 part of the eye is diseased, although the retina, so universally 

 admitted to be the seat of vision, is in a healthy state. 



The physiological or mechanical seat of touch lies at the 

 end of the fingers, at the ends of the toes and tongue, and in 

 the lips, that is, the qualities of bodies are rendered percep- 

 tible to the sensory through the agency of these parts of the 

 body. No one supposes that the seat of touch resides in any 

 particular part of the skin itself, whether finger, tongue, or 

 lip. The sensation of touch is produced by direct pressure, 

 a pressure which is instantaneous, which commences at the 

 point of contact, and ends in the brain, whence the mind takes 

 immediate cognizance of it. 



So it is with all the senses ; there is an instantaneous com- 

 munication between the outward points which come into con- 

 tact with tangible bodies and their qualities, and the central 

 point in which consciousness dwells. 



Seeing, being the most complicated of all the senses, re- 

 quires a more complicated apparatus to convey impressions to 

 the mind. The different parts are for the admission, the modi- 

 fication, and the absorption of light, whilst amongst this curious 

 machinery the adjustment and continued action of these se- 

 veral parts are maintained by certain muscular and valvulous 



* We apprehend that this is not the case. Although it is certainly stated 

 by some medical writers that the appearance of these muscce volit antes t as 

 they are termed by pathologists, indicates in certain cases the commence- 

 ment of amaurosis, yet they do not, we believe, actually constitute any form 

 of that disease. — Edit. 



Third Series. Vol. 5. No. 27. Sept. 1834. 2 C 



