HISTOLOGY OF THE VITREOUS HUMOUR. 353 



vesicle. In fully developed cells of this kind a single vesicle 

 only exists, which completely fills the entire cavity, and only 

 leaves a little space at the periphery for a nucleus surrounded 

 by a small quantity of protoplasm. Sometimes two vesicles 

 occur, separated from each other by a straight line. In other 

 cases there are several vesicles which appear to be surrounded 

 by a common sheath, the contour of which is perfectly 

 spherical. 



The vesicles just described are not only found in the round 

 cells, but are seated also on the processes of the stellate cells ; 

 where they sometimes attain a colossal size, exceeding that 

 of the cells themselves. We meet with these at all periods 

 of life, though chiefly in old people, and in the posterior, por- 

 tions of the vitreous. 



All these cells possess the property of contractility. They 

 change their form and perhaps also their place. The contracti- 

 lity of the round cells containing vesicles is less in proportion 

 to the size of the vesicles, and the more consequently the pro- 

 toplasm has diminished. 



The views in respect to the existence and the nature of the cells are 

 as various as those on the structure of the stroraa. 



We are indebted to Virchow for the first special investigations that 

 were made upon the cells. In the embryo of a Pig four inches in 

 length he found, distributed at tolerably regular distances through the 

 homogeneous intercellular substance, round, nucleated, sometimes 

 multinucleated and coarsely granular cells. 



According to Kolliker, the cells occur especially in young persons ; 

 he saw them indeed in some adults, but scattered and indistinct, and 

 chiefly near the lens and hyaloid membrane. Weber, on the other 

 hand, found stellate anastomosing cells throughout the whole vitreous. 

 Hannover and Finkbeiner describe an epithelium covering the hyaloid 

 membrane, and this, according to the last-named author, invests also 

 the several septa in its interior. The same view is also entertained by 

 Coccius. Ritter observed an epithelium with ramified cells only on 

 tbe internal surface of the hyaloid, but no cells, on the other hand, 

 within the vitreous. 



The fibres of the zonula, as has been already stated, spring 

 from the vitreous, and from that part of it which has not yet 

 reached the ora serrata retinae. The zonula-fibres arise near 



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