'(669) 
Eye, it cannot be doubted, but that this deficiency of Vifion 
15 upon the optick Nerve. 
1 his Difcovery I communicated to many of my friends, who 
found the fame thing, though not always juftac the fame diftan- 
ces-, 'which diverfity Iadfcnbed to the different fituation of the 
Optick Nerve. You have made it your felf,in his Majefltes Libra- 
ry y where I (hewed it to thofeof your llluftrious Affemhly^ and 
you as well as I, found the like variety, there being fome, who, 
at the diftances mention d, loft the fight of a Paper, 8 inch, large, 
and others ; who ceafed not to fee it, but when it was fome- 
what lefs-, which appears not how it can becaufed but by the 
differing magnitudes of the Optick . Nerve in different Eyes/ 
This Experiment hath given me caufe to doubt, Whether 
Vifion was indeed perfonrfd in the Retina (as is the Common 
opinion) or rather in that other Membrane,which at the bottom 
of the Eye is feen through the Retina, and is called the chord- 
des. For if Vifion were made in the Retina , it feems that then 
it fliould be made whereever the Retina is ; and fince the fame co- 
vers the whole Nerve, as well as the reft of the bottom of the 
Eye, there appears no reafon tome, why there lbould be no Vi- 
fion in the place of the Of tick Nerve where it is: on the contra- 
ry., if it be in the Choroids that Vifion is made, it feems evident, 
'that the reafon.why there is none on the optick Nerve, is,becaufe 
that that Membrane (the Choroides) parts from the Edges of the 
faid Nerve, and covers not the middle thereof, as it does the reft 
of the bottom of the Eye. 
Upon this, I defire, you would give me your thoughts with 
freedom, fince I am none of thofe that love to obtrude Conje- 
ctures for Demonftrations. 
T o which the main of M. Pecquets Anfwer if, as follow es y 
Very one wonders,that no perfon before you hath been aware 
of this Privation of Sight, which every one now finds, after 
you have given notice of it. But as to the Sequele^ you draw 
from this Difcovery, I fee it not cogent, to abandon the Plea 
of the Retina for being the principal Organ of Vifion. For (not to 
infift here on other confiderations) it will be fufficient, now to 
takenotice, that at the place of the of tick N-erve there is fome- 
