236 Scientific Proceedings, Royal Dublin Society. 
perhaps faintly. This involved a visual perception in the mind, 
faint, but sufficient on this occasion to be seen with sufficient dis- 
tinctness when not overpowered by objects seen in the ordinary 
way through the eyes. 
The experience I had myself was one which frequently occurred 
tome whena lad. Several of us boys were fond of witnessing 
sham fights in the Phoenix Park, at which some of the most con- 
spicuous objects were the single horsemen who now and then 
galloped at full speed, with orders, from one part of the field to 
another. Almost always, after a day spent in viewing this spectacle, 
as I lay in bed at night I saw vividly what seemed to be a tiny 
horseman galloping violently from right to left, or from left to right 
asthe case might be. All the movements of the horse were repro- 
duced, the dashing about of the sabre-tasche, the coloured uniform, 
the movements of the horseman. It cannot have been in the retina 
that this revival took place. It must have been in a much more 
deep-seated part of the brain. 
It would, I think, be of very great interest to ascertain from 
the inhabitants of a blind asylum, whether those who have recently 
had their retinas extirpated, or rendered functionless, continue to 
dream of scenery, so long as the memory of visual perceptions is 
recent. I should expect they would, as the structures which 
they have lost do not seem to be concerned in either memory or 
dreaming. 
From a review of all the evidence it appears clear that the retinal 
image isonly one of the stepping-stones in a rather long progress 
from the object in nature to the event in the brain, which is the 
direct adjunct of visual perception. Why, then, it may be asked, is 
an image necessary? Why is it never absent ? Why is not some- 
thing quite different sometimes substituted for it P The following 
is, I think, a sufficient answer. There must be some difference in the 
events occurring in the occipital lobe in order that two points of an 
object may be seen distinct from oneanother. ‘To bring this about 
either a different nervelet must have been acted upon in the organ 
of sight, or the same nervelet must have been differently acted on. 
In the case that actually occurs, it would appear that a different 
nervelet is acted upon when the points of the object are sufficiently 
separated to be seen as two, and that a difference of action on the 
same nervelet is reserved for exhibiting to us variations of bright- 
