11 



surprising that v. Lenhossek should have overlooked the more 

 numerous, more massive, and more prominent fibers arising from the 

 retina. The retinal fibers, moreover, are a permanent formation, 

 as will appear from further study; the lenticular fibers are very 

 early separated from their mother cells by the formation of the lens 

 capsule, as v. Lenhossek himself points out. Wolfrum is of the 

 opinion that the lenticular fibers serve as an apparatus for retaining 

 the lens vesicle in its place after it has separated from the body 

 ectoderm. The peculiar shape of the lens vesicle at this time seems 

 to lend color to this theory. Whether or not the lens fibers contrib- 

 ute to the formation of the primitive vitreous body, their influence 

 is neither predominant over, nor equal to, that of the retina, while 

 after the formation of the lens capsule, no further connection exists 

 between the lens and the vitreous body. Kolliker says of v. Len- 

 hossek 's theory : The lenticular vitreous body of v. Lenhossek does 

 not exist (page 18). 



The purely retinal, i. e., ectodermal origin of the primitive 

 vitreous body, as described in this chapter, has found defenders 

 in many modern investigators. It may suffice to mention Tornatola, 

 Addario, Wolfrum, v. Szily, v. Kolliker, Mavas, Magitot, and See- 

 felder. Mavas and Magitot thus sum up the results of their in- 

 vestigation on the origin and the development of the vitreous body 

 in the human eye : The primitive vitreous body is of retinal original. 

 It consists of a very delicate fibrous mass, arising from the marginal 

 zone of the embryonic retina. This marginal layer is formed by 

 protoplasmic prolongations of the supporting cells, which are the 

 first to differentiate in the inner layer of the optic vesicle. The 

 primitive vitreous body is, therefore, an exoplastic formation of this 

 layer (page 127). 



II PERIOD OF MESODERMAL INVASION OF THE VITREOUS BODY 

 The primitive simple condition of the vitreous body soon under- 

 goes a radical change, brought about by the entrance of the complex 

 hyaloid vascular system and numerous mesodermal elements. The 

 relationship of these structures to the vitreous body is of paramount 

 importance in judging of the true character and the further develop- 

 ment of the latter. 



The hyaloid artery, a branch of the arteria centralis retinae, 

 entering the optic cup through the still partly open choroid fissure, 

 at first appears as a single solid trunk, pushing its way far into the 



