19 



to determine the structure and the nature of these cells, but nowhere 

 does there appear any connection between them and the vitreous 

 body fibers. 



The vitreous body proper is represented by a great mass of very 

 delicate fibers, arising exclusively from a small region of the anterior 

 portion of the retina, the pars coeca retince. From here they descend 

 in fairly heavy bundles towards the center of the bulbus in the 

 region of the optic nerve. Several of these fiber bundles pass closely 

 along the retina, while the others grow slightly inward in the direc- 

 tion of the lens and then turning backward join the first near the 

 optic nerve (Figure 18). Between these two heavier portions of 

 the vitreous body we have a rather large space filled with an irregu- 

 lar mass of fibrous tissue. The vitreous body, therefore,- is com- 

 posed of two rather prominent masses or layers of fibers, the one 

 forming the outer portions near the retina, and the other lining the 

 hyaloid canal, while the intervening region contains a very loosely 

 arranged fibrous mass. The outer portion of the vitreous fibers has 

 been quite generally held to be a special membrane and called the 

 hyaloid membrane. Careful investigation shows that the vitreous 

 fibers are, indeed, more closely arranged in this region, but they do 

 not coalesce to form a distinct membrane. The internal limiting 

 membrane of the retina seems rather to be common to both the retina 

 and the vitreous body. This view is held by most recent investiga- 

 tors (Kolliker, Szily, Wolf rum, Mavas, Magitot, Seef elder, Szent- 

 Gyorgyi), who insist that the supposition of the existence of a mem- 

 brane enveloping the vitreous body and distinct from the internal 

 limiting membrane of the retina is not based upon fact. In this 

 connection we may call attention to the peculiar fact that, when 

 shrinkage of the vitreous body takes place, the retinal membrane 

 quite generally adheres to the vitreous body, which shows the inti- 

 mate union of the two. The inner mass of vitreous body fibers 

 separates the vitreous body proper from the so-called hyaloid canal. 

 This portion of the vitreous body, the existence, size, and real struc- 

 ture of which have been the subject of much controversy, is clearly 

 shown in figure 18. 



Figure 17 shows its relation to the other parts of the eye, its rela- 

 tive size and its shape. It roughly resembles a funnel, with its mouth 

 towards the lens, and the stem surrounding the optic papilla. While 

 quite narrow in the inner portion of the eye, it widens very much 



