24 



forty, were traces of the hyaloid artery found, and even in these 

 two the independent formation of the hyaloid canal was plainly 

 shown. 



Our own results may be summed up thus : the hyaloid canal, or 

 the hyaloid portion of the vitreous body, formed by a denser ar- 

 rangement of the vitreous fibers and including a loose and irregular 

 fibrous tissue, is a constant structure in the eye of the adult pig. It 

 is of almost uniform width throughout, and extends through the 

 entire posterior chamber of the eye from the optic disc to the lens, 

 from which it is separated by the thin membranelike lining of the 

 fossa patellaris. In rare cases it contains remnants of the hyaloid 

 artery, which, however, show no relationship to its walls. The hya- 

 loid canal in the eye of the adult pig, is, therefore, not a temporary 

 formation nor is it to be attributed to the hyaloid artery. 



Szent-Gyorgyi, who has made extensive investigations of the 

 structure of the hyaloid canal in the eyes of adult animals, including 

 the pig, maintains that the relationship of the vitreous body fibers 

 to the ciliary portion of the retina is a secondary formation, attrib- 

 utable to the tendency of the vitreous fibers to attach themselves to 

 any structure near them, and that in consequence this relationship 

 does not warrant a conclusion as to the origin of these fibers, which 

 must be sought rather in the vitreous body itself with its native 

 faculty of growth and differentiation. But it is plain that the 

 structure of the adult eye does not of itself reveal whether the con- 

 ditions found there are primary or secondary. Nor is it always 

 safe to attempt the reconstruction of the ontogeny of a species from 

 its supposed phylogenetic development. Only the careful study 

 of the various phases of embryonic development shows whether the 

 union between the vitreous fibers and the ciliary retina is a secon- 

 dary formation or has genetic significance. A comparison of figures 

 8 and 19 reveals at once the untenability of Szent-Gyorgyi 's 

 opinion, and disposes at the same time effectively of the view of 

 Lenhossek, adopted and modified by his brilliant followers, v. Szily 

 and Szent-Gyorgyi, that the vitreous body, separating from its place 

 of origin, becomes a syncytium, capable of independent nutrition, 

 growth, differentiation and regeneration. The union between the 

 vitreous body and the ciliary retina can be traced uninterruptedly 

 from the first appearance of the vitreous fibers to the formation of 

 the permanent vitreous body. The latter, therefore, no less than 



