Page:Philosophical Transactions - Volume 013.djvu/189

 image; and lastly sensation could be better continued to the Tense Fibres of the Pia mater by the one, then to the brain by the softer of the other.

Although this last Objection does not directly strike at my Notion of Vision (because a correspondence of Fibres may be understood as well in one as t' other); yet it may not be amiss to consider it particularly; because I have formerly asserted and do still, that Vision can be no way better performed then by the Fibres of the Retina, however other senses may require in their action a greater stiffness in the Membranes that are subservient to them, which some of late will have to be the only instruments of sense. First then it is certain that (as I said before) the Retina is no more transparent if so much as the oiled paper in the lantern, which yet serves well enough to intercept the turning images of it. Secondly, That being of a whitish colour, and resembling thereby the white Paper in the dark house, it is fitter to receive the images of colour'd objects then the dark shade of the Choroeides. Thirdly, It being the more inward or medullary expansion of the Optic Nerve it can more immediatly transmit any motions to the Meditullium of the brain (or the common sensory) then the other part, which by its continuation to the pia mater does not reach it; and this I urg'd formerly, which has not yet been answer'd by any of Monsieur Mariotte's followers. Fourthly, The blood-Vessels running upon it is as well an objection against the Choroeides (if the latter be not chiefly a Plexus of the same as has been lately well argued), because this Coat lies under the Retina, and consequently under them too and therefore hereby is only prov'd that in some positions of our body, or in some Stations, we do not so well view an Object as in others, and this is very true. Fifthly, As to the Tensness of the Fibres, I before observ'd that the Retina has as much as those of a Spider's Web, and this is sufficient, nay more suitable to the finer stroaks of the etherial or lucid matter and the nice actings of this sense, which is not re-