Prof. Anders.. n Stuart. [F. 



differs from those formerly given by me, in that T now consider the 

 membrane limiting the canal of Petit posteriorly as an artificial 

 product, the result of the action of reagents (by precipitation or con- 

 densation). There I agree with Iwanoff. I am bound, however, to 

 maintain, in opposition to Meckel, the existence of tlie canal of Petit, 

 such as I have described it ; that the zonula and the vitreous body 

 appear to .touch each other is but the result of the compression which 

 they undergo during section. And so a cleavage of the hyaloid near 

 the ora serrata does not take place." Iwanoff says, "In the vicinity 

 of the ciliary processes the vitreous separates itself from the zonnla, 

 so that its entire anterior surface, or that which is turned towards 

 the canal of Petit and the lens, is not covered by any special mem- 

 brane; neither by a prolongation of the limitans, as stated by Henle, 

 n'>r by a special membrana hyaloidea, as was formerly supposed." 

 Then, "At the ora serrata the several concentric layers of the cortex 

 (of the vitreous) are so crowded together that the surface of the 

 nucleos is separated from the limitans only by a very thin but plainly 

 fibr< us layer. The fibres of this layer run parallel to the surface of 

 the \ iiieous in wavy bundles, and are .not unlike bundles of connective 

 tigsae=. The entire layer, thus changed, finally turns and passes 

 towards the axis of the eye, thus completely covering the anterior 

 snrface of the vitreous. Since we here, in fact, have not a single but 

 several layers crowded together, and only loosely united with one 

 another, it is easy to see how one might suppose that behind the lens 

 there lay a special membrane covering tlie corpus vitreum, especially 

 since the most superficial of these layers is perfectly smooth." Finally, 

 " The tissue of the vitreous is here condensed to form a limiting layer, 

 in the same manner as Bowman's membrane is formed by a condensa- 

 tion of the snbstantia propria of the cornea ; an independent membiane 

 the hyaloidea does not exist at this place." 



What occurs to me then, considering the eminence of the authori- 

 ties on each side of the question, is that the methods of demonstration 

 have not been sufficiently conclusive. After seeing it as I have seen 

 it, nnd shown it to others, I cannot for one moment doubt its existence, 

 for the proof of its existence could not possibly be more conclusive 

 if c;m even be dissected off and examined in any perfectly fresh 

 unaltered ox eye. 



As Aeby has already:, I find, published, the eyeball is best left to 

 decompose for some twenty-four "hours or longer, according to the 

 external temperature, and then, on opening the sclerotic and choroid 

 tissues carefully with fine blunt-pointed scissors, the vitreous and lens, 

 nnited by the suspensory ligament, drop out in a mass, or at least 

 nre very easily expressed. The suspensory ligament is now snipped 

 all round, and the lens in its capsule removed. 



When this has been done, according to the one side, the bed of the 



