The nomenclature of the cranial nerves adopted by Manfredi is taken from Mondino and is almost identical with that of Galen, whose classification is summarized above.[194] Manfredi’s description of Galen’s fourth pair is confused and inadequate, but his account of Galen’s sixth pair is an improvement upon Mondino.
The ‘rete mirabile’ is an interesting survival of Galenic anatomy. This structure is hardly present in man, but is developed in the lower animals, and especially in calves, upon whose bodies Galen worked. The father of physiology regarded the ‘rete mirabile’ as the place where the psychic pneuma was elaborated.[195] Galen’s findings in the lower animals were assiduously transferred to the human body, to which his descriptions are much less applicable, while his views on the pneuma lasted in more or less misunderstood form well into the seventeenth century.
(b) THE EYE
Tractate i, Chapter 3
(folio 11 recto) The socket of the eye is not over-depressed, for it has to receive the images (spetie) of visible things. Nor does it project greatly, lest it should be liable to injury from exterior violence. For the eyes of man being very soft and susceptible, nature provided eyebrows as a shield above, and eyelids as protectors in front, and made moreover the projections of the maxillae and the nose, so that the eyes should be guarded on every side. So great was the solicitude of nature for these members.
Seven are the tunics of the eye and three its humours. Three front coatings join with three coatings at the back like six shields, the edges of every pair joining each to each, the outer being larger and containing the others. The seventh tunic is largest of all, and encloses the whole eye, and therefore it is called conjunctiva because it joins and surrounds the whole eye except the place where the pupil is, and that small part [is covered] by the cornea. Now this first tunic where it covers the outside part is seen to be white.
The second tunic in its front part is called cornea because it resembles horn in its substance and colour; and this covering is transparent, so that the images of visible things may penetrate through it. And it is also solid and large and composed of four membranes, so that being near external things it should not receive hurt. With this [corneal tunic] is united posteriorly another tunic [the third] called sclerotic, i.e. hard. These two coverings have their origin in the membrane about the brain, that is in the dura mater, just as the first tunic arises from the membrane over the skull, called almochatim.
The fourth tunic as to its front part is called uvea [because] it is like a seed of a black grape, and in its midst is a hole called the pupil. Nature made this tunic opaque so that the visual spirit should be conserved and not dissipated by the light outside. Moreover nature made the opening in the tunic that the image might penetrate freely; while it is narrow, so that the visual spirit should be concentrated. Thus when the said pupil, or rather hole, dilates more than usual, either naturally or accidentally, the sight becomes imperfect. [The uveal tunic] joins posteriorly the fifth tunic, called secundina because it is made like the after-birth, i.e. the membrane in which the child is enveloped in its mother’s womb, and it arises from the pia mater.
The sixth coating in front is called arachnoid because it is formed after the manner of a spider’s web, and posteriorly it joins the seventh coating, called retina, because it is made like a net.