57 2 VITREOUS BODY. [SECT. 228. 



lias also found mucus in the vitreous body of the adult, Virchoiv 

 believes himself warranted in classifying the tissue of the em- 

 bryonic corpus vitreum with what he calls ' mucous tissue/ but 

 which I regard as embryonic connective tissue (see § 23); and he 

 further assumes, that in the course of development the structure 

 undergoes a change, by which the cells perish and the intercellular 

 substance alone remains. For my own part, an examination of 

 the vitreous body in the embryoes of man and of animals, as well 

 as in children and young animals, has revealed to me nothing else 

 than a homogeneous, muciferous matrix, with numerous, granular, 

 nucleated cells, round or elongated, and measuring croo^" to 

 001'", distributed pretty regularly through it at distances of O'Oi" 

 to o - o2'", or even 003'". I have also observed stellate anastomosing 

 cells, but always on the outer side only of the hyaloid membrane, 

 and these were readily demonstrated to be developing capillaries, 

 obtaining a connection with the well-known vessels external to 

 the hyaloid, as soon as those vessels began to convey blood. I have 

 never seen with the microscope any positive trace of the mem- 

 branes which are described by Hannover in the vitreous humour; 

 and yet I venture to assert, that such membranes, if they existed, 

 must be just as easy of recognition in their folds as the extremely 

 delicate hyaloid membrane itself. In the vitreous body of the 

 adult, only the homogeneous matrix was found to remain, the cells 

 having disappeared. I have often, however, met with scanty and 

 indistinct remains of these cells, especially in the parts of the 

 vitreous humour adjoining the lens and the hyaloid membrane. — 

 From these observations, I draw the conclusion, that the vitreous 

 body does possess, at an early period, a kind of structure which 

 most resembles embrvonic connective tissue; but that subse- 

 quently, at least in its inner parts, every trace of this structure 

 disappears, so that it comes to consist exclusively of a more or less 

 consistent mucus (see § 23). 



Zonula Zinnii. — At the ora serrata, the vitreous body comes 

 into intimate contact with the retina, and this again with the 

 choroid, so that it is extremely difficult to elucidate the true con- 

 dition of the nature of the structure which has been above de- 

 scribed as the zonule of Zinn. If it be exposed from M'ithout, 

 black pigment from the ciliary process always remains adherent to 

 it at certain spots, and often for a considerable extent. If places 

 be chosen for examination where this is not the case, the zonula 

 is found to have an outermost greyish layer, which extends exactly 

 to the point where the ciliary processes join with the zonula, and 



