The Greater Work (Opus Majus), Vol. 2

CHAPTER III.

The humours of the eye.

And this tunic contains within itself three humours and one web. For from the anterior part of that tunic arises one small and subtle web in the manner of a spider's web, and in this is contained the body that is called the glaciale icy body or crystallinum crystalline lens, or grandinosum hail-like body, and this body is placed directly upon the extremity of the nerve. But it has two parts; one is interior near the extremity of the nerve, and is similar to liquefied glass, for which reason it is called the vitreus vitreous humour. The other anterior part is similar to ice, and hail, and crystal, whiter than the vitreous humour, and is called the anterior glacialis, not having another proper name among the author of perspective. But it is called among others the crystallinus crystalline humour, or glacialis, or grandinosus, because it is similar to them, and the whole body contained within the web is thus called from this part of it. Then towards the anterior of the eye, outside the web, one humour similar to the white of an egg fills the anterior concavity of the uvea, and on one side it touches the anterior of the glacialis, and from the other it enters the hole of the uvea, and it touches up to the cornea, so that the spherical convexity of this humour touches the concavity of the cornea, and it is called the albugineus aqueous humour. There will be, therefore, the cornea, and the albugineus humour, and the glacialis, and the vitreus, and the extremity of the nerve consequently, so that the species of things may pass through the middle of all of them up to the brain. And Avicenna says in the fourth book On Animals that the retina leads nourishment in truth to the parts of the eye, and it contains the vitreus, as Constantinus says, and the author of perspective agrees, wishing that the lower part of the uvea should contain the vitreus humour, and at the end of its course carrying blood in its veins and arteries well-digested, by which the vitreus humour may be made and nourished, insofar as the vitreus can nourish the crystallinus humour. For, as Avicenna says in the third book of Medicine, the vitreus humour is the nourishment of the crystallinus. And Constantinus says this. Hence, because the crystallinus is overly white and clear, blood is not suitable for it as immediate nourishment, but it needs nourishment intermediate between blood and the crystallinus, and of this