SECT. 230. J VESSELS OF FGETAL EYE. 579 



The vessels which occur in the eye of the foetus, even in the 

 transparent media, present many points of interest. The vitreous 

 body possesses on its outer surface, between the hyaloid membrane 

 and the retina, a pretty wide vascular network, which is supplied 

 by branches distributed from the arteria centralis retinae at its 

 entrance into the eye; anteriorly at the border of the lens, this 

 network forms a circular vessel upon the zonule of Zinn, the cir- 

 culus arteriosus Mascagnii, from which vessels then proceed to 

 the membrana capsulo-pupillaris, to be immediately described. 

 Besides these vessels, a special arteria Ju/aloiclea, likewise derived 

 from the arteria centralis retinae, passes through the vitreous body 

 in the so-called hyaloid canal directly to the lens, and ends in a 

 multitude of branches, which join at very acute angles, in a mem- 

 brane lying close upon the posterior wall of the capsule of the 

 lens. This membrane is, indeed, a part of an outer vascular 

 capsule, which at first accurately surrounds the lens ; and whose 

 anterior wall is supplied by continuations of the hyaloid artery 

 round the border of the lens, together with branches which unite 

 with this vessel from the circulus arteriosus Mascagnii, and the 

 anterior border of the uvea. Subsequently, when the lens retracts 

 from the cornea on which it was at first closely applied, and the 

 iris buds forth from the border of the uvea, the anterior wall of 

 the vascular capsule of the lens is divided into two parts; a middle 

 anterior part, which proceeds from the pupillary margin of the iris, 

 and is connected with this membrane by vessels so as to close the 

 pupil {membrana puj ilia lis) ; and, secondly, an outer posterior 

 part, which passes backwards from the same point to the border 

 of the lens (membrana capsulo-pupillaris). The more the iris and 

 the chambers of the eye are developed and the lens recedes, the 

 more distinct this latter portion of the vascular capsule becomes; 

 till at last it appears as a delicate membrane traversing the 

 posterior chamber of the aqueous humour. The venous blood of 

 all the parts mentioned, is returned by the veins of the iris, and 

 the blood of the outer surface of the vitreous body returns also by 

 the veins of the retina, and perhaps, also, by a vena hyaloidea 

 (whose existence is doubted by many authors, and never observed 

 by myself), which is said to take the same course as the arteries. 

 With regard to the genetical signification of the vascular capsule, 

 nothing has hitherto been ascertained concerning it. I found it 

 composed of a homogeneous tissue, with a few interspersed cells ; 

 and I regard it as a structure corresponding to the cutis, which 

 becomes detached from the general integument along with a part 



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