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On the Eye |
Excerpted from Opus Maius V, Perspectiva 1 |
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Therefore the eye has three tunics, or little garments, and three humors, and one web like a spider's web. And its first tunic comes from the innermost tunic of the nerve, which comes from the pia mater according to all authors. And it expands from the extremity of the nerve where it enters the fissure of the bone, and it branches out like a concave net (rete) into its first part. Therefore it is called the rete or retina, according to Avicenna in his third book on medicine and also according to Constantine, and it has veins, arteries, and fine nerves. Then its second part is coarser, as Avicenna says, and it expands spherically to the front of the eye, having a fissure in the middle of its front part, so that the species of light and color and of other visible things is able to go through the middle of the eye to the nerve that comes from the brain. Et a tunica nervi que venit a dura matre secundum omnes expanditur secunda tunica oculi, que habet duas partes. Nam prima pars componitur ex venis et nervis et arteriis, et vocatur secundina, quia est similis secundine. Et secunda pars expanditur usque ad cuiusdam spere que circulatur super extremitatem uvee; et est sicut cornu clarum, et ideo vocatur cornea. Tertia tunica oculi fit ex illa pellicula nervi tertia que venit a membrana cranei; et eius pars prima coniungitur ossi oculi, et ideo est dura et solida, et ideo dicitur sclyros. Aliqui etiam voluerunt esse pauciores, et hoc mulitiplici consideratione; sed de hiis non est curandum, quia violenta est eorum interpretatio et deviat a recta ratione. Aliqui etiam septem tunicas posuerunt; sed falsum est, quia telam araneae pro tunica computaverunt, cum non sit. Et illi qui dicunt tres esse totam primam tunicam vocant uveam; et totam secundam vocant corneam; et totam tertiam vocant consolidativam. |