480 Dr Autson on Single and Correct Vision, by means of 
those which follow impressions made on different points of the sur- 
Jace of the body. 
I.. Of the first of these facts, 7. e. the single vision by means 
of double images, it is well known that an explanation was pro- 
posed by Newron, fully considered by Rerp, and since support- 
ed by Wotxasron (often calied the Theory of WoLtuaston, but 
quite incorrectly), proceeding on the supposition of a semi-decus- 
sation of the human optic nerves at their commissure ; whereby 
the fibres, from the right half of the retina of each eye, go to the 
right optic fobe* in the brain, and vice versa; the consequence 
of which may probably be, that the fibres which connect them- 
selves with, or terminate at corresponding points of the retine, 
may originate at the same points in the optic lobes. If this be 
so, impressions made on corresponding points of the retinz are in 
fact impressions made on the same points in the optic lobes ; 
and, as they are effectual in exciting sensations in the mind, 
only inasmuch as they are made on the optic lobes, they must 
necessarily co-operate in exciting the same sensations. 
Dr Rerp fairly admits that, if the anatomical part of this 
theory were ascertained to be correct, “it would lead us a step 
forward in discovering the cause of the correspondence and sym- 
pathy of the two retine ;’—he ought rather to have said—the 
cause of single vision by impressions made on corresponding 
points of the two retine. I think we may add, that it is the 
only step which we can conceive to be taken, or can desire to take, 
in that inquiry. And I will farther venture to maintain, that a 
precisely similar step may be taken, even with more confidence, 
as to the correct vision by means of inverted images. 
We must admit, that the anatomical evidence of the theory 
* The term optic lobe is here used as a short expression for that portion (per- 
haps not yet absolutely determined) of the contents of the cranium, from which the 
optic nerves originate, and on which their sensibility depends. 
