264 SPECIAL ANATOMY. 



with their anterior extremities, in order to attach themselves to the 

 Sclerotica ; so that, in consequence of the thickness and strength 

 of the capsule, each passes away, as it were, over a trochlea. 



a. The most external of the coats of the eye. They determine 

 the shape of the organ. They are the stiff Sclerotica and the 

 transparent cornea. 



497. 1. Sclerotica (s. tunica albuginea s. cornea opaca), 



the white coat. 



a strong, opaque membrane, forms a segment of a sphere, the anterior sixth 

 of which is represented by the transparent cornea. It consists of short fibrous 

 fasciculi interlacing with each other in every direction, is bluish, brilliant 

 (inwardly brown), provided with few vessels, and not at all with nerves. [?] 

 Rigid, and not extensible, it is thinnest anteriorly in the neighbourhood of the 

 Cornea, behind, where a foramen for the Optic nerve perforates it, thickest. 

 The foramen for the optic nerve lies rather internally to the axis of the globe. 

 The external surface of the Sclerotica is covered before by the conjunctiva 

 connected with it by loose uniting tissue, and by the tendons of the mus- 

 cles of the globe. The internal surface is wrinkled, brown, and connected 

 by delicate uniting tissue and the obliquely passing ciliary vessels with the 

 tun. Choroidea. The ciliary nerves pass from behind forwards between the 

 two coats. 



The anterior border is circular, bevelled off on the internal surface ob- 

 liquely backwards (sulcus Sclerotica), for the reception of the corresponding 

 bevelled border of the Cornea. Both are firmly united together. Between 

 them and the ligam. ciliare, which is here, also, attached, we find (in animals) 

 sinus circularis venosus iridis s. canalis Fontante, a very narrow circular 

 canal which receives the veins and the blood of the iris, which is driven 

 out from these during enlargement of the pupil, and is said to give off vv. 

 ciliares anticce ; but in Man it is placed in the substance of the Cornea (as 

 canalis Schlemmit). 



The Sclerotica is to be considered as a continuation of the dura Mater upon 

 the Optic nerve ; [?] the pia mater and arachnoidea do not pass into the eye. 

 At the foramen for n. opticus a lamina cribrosa was formerly described, that 

 is, a perforated plate which apparently arises from the manner in which the 

 neurilemma leaves the fasciculi of the n. Opticus at this place. 



Vessels : a few arteries from artt. ciliares ; Veins more numerous, in con- 

 nexion with the canals of the Cornea; Lymphatics are probably present. 

 Nerves not yet demonstrated. 



498. 2. (Tunica) Cornea, the transparent Cornea, 



is a thick, transparent, strong, but elastic membrane, forming the segment of 

 a smaller (also more convex) sphere than the Sclerotic, and the anterior part 

 of the bulbus. Its anterior convex surface is covered by Epithelium, a conti- 



