396 SPECIAL HISTOLOGY. 



a vascular circle, the circulus arteriosus Mascagnii, from 

 which again vessels are given off to the membrana capsulo- 

 pupillaris, presently to be described. Besides this, a special 

 arteria hyaloidea, also derived from the central artery of the 

 retina, runs in the so-termed canalis hyaloideus, in a straight 

 line through the vitreous body, to the lens, and ramifies in the 

 most elegant arborescent manner, at very acute angles, in a 

 membrane closely applied to the posterior wall of the lenticular 

 capsule. This is nothing else than a portion of an external 

 vascular capsule, which at first very closely surrounds the lens, 

 and in its anterior wall is supplied by the continuations of the 

 hyaloid artery, coming round the border of the lens towards 

 the front, with which branches of the circulus arteriosus 

 Mascagnii and of the anterior border of the uvea are con- 

 nected. Afterwards, when the lens retreats from the cornea, 

 with which it is, at first, in close apposition, and the iris buds 

 out from the border of the uvea, the anterior wall of the vas- 

 cular lenticular capsule is divided into two portions : one central 

 and anterior, which, arising from the border of the iris, and 

 connected with that membrane by vessels, closes the pupil — 

 the membrana pupillaris ; and another, external and posterior, 

 extending backwards from the same points upon the border of 

 the lens — the membrana capsulo-pupillaris . The latter becomes 

 more and more distinct as the iris and aqueous chambers are 

 developed and the lens retreats, until at last it represents a 

 delicate membrane stretching across the posterior chamber. 

 The venous blood from all these parts is returned through 

 the veins of the iris, and from the outer surface of the vitreous 

 body, also through those of the retina, and perhaps through 

 a vena hyaloidea, said to take the same course as the artery, 

 but of the existence of which many authors doubt, and which 

 I have never myself seen. With respect to the genetic import 

 of the vascular capsule, nothing has as yet been ascertained. 

 I find it to be composed of a homogeneous tissue, with a few 

 scattered cells, and regard it as a structure corresponding to 

 the cutis, which, in the formation of the lens, is detached 

 from the skin, together with a portion of the epidermis, and 

 remains in the eye. The vitreous body, then, may be under- 

 stood as modified subcutaneous connective tissue, — a supposi- 

 tion not at all incongruous with the observations above 



