0fO 
things that may very welt caufe this lofs of the Objeft. There 
are the Fejjels of the Retina, the trunks whereof are big enough to 
give a hindrance to Vifion, Thefe VdTels, which are no other but 
the ramifications of the Veins and Arteries, are derived from the 
Heart, and having no communication with the brain, they can- 
not carry thither the Species of the Obje&s. If therefore the Vi= 
fual rays, itfuing from an Objed^fall on thefe Veflfels at the place 
of their Trunk or main Body, 'tis certain that thelmpreilion, 
made thereby, will produce no Vifion, and that the pi&ure of 
that Object will be deficient as when on a white paper in an ob- 
fcure Chamber, there is fome black fpot, or in it feme hole con- 
fiderably bigg : for the more fenlible this blacknefs or hole is, the 
more of the image of the obje<5l it intercepts from our Eyes. It 
Is not fo in refpedl of the fmall ramifications, that iflTue from thofe 
trunks, and fhoot into the Retina. For if they be met with 
at the place of the bottom of the Eye, where Vifion is made di- 
ftin&^they will not render the image of the Object deficient, be- 
caufe they are fo fmall, as not to be fenfible. Thus it is, that in 
Looking-glaflfes, when they want lead or tin in any place big 
enough to be perceived, the image, we there fee ; appears to have 
a hole 5 which happens not, when there is but fo fmall a one, as 
might be made by the point of a needle. 
Thus much being obferved as to the dedu&ion, made from this 
Experiment , I fhall further note, That that paper, the fight 
whereof is loft, muft be further or nearer off, according to the 
diverfity of the ftru6ture of Eyes. For fome loofe this pa- 
per at the diftance of two feet , fome at a lefs, others at a great- 
er diftance fome loofe it a little higher, others a little lower, ac- 
cording as the trunks of the veflfels are fituated in refpedi of the 
Optick Nerves and fome loofe more of it than others, accord- 
ing as thofe veflfels are bigger or fmaller. ftnd becaufe 'tis hard to 
determine precifely the place, where the object is loft in all forts 
of Eyes, we have ground to believe, that this lofs is not always 
made on the extent of the Nerve, where the Retina is, but fome- 
rimebefides it, where the chorofdes is found. For the trunks of 
the Veflfels of the Retina are big and long enough to extend on 
this or that fide of the Nerve, and fo to hide fome part of the 
cborotdes, according to their Magnitude. And in this cafe it will 
be 
