10 



investigation will show that this primitive condition of the vitreous 

 body, although obscured and modified by the ingrowing mesoderm, 

 remains essentially the same. A comparison of figures 2 and 19 

 shows rather that the mesodermal elements are only temporary 

 structures in the vitreous body, which both in its primitive and in 

 its final stage of development is purely ectodermal. 



Neither do our observations agree with the views of Kessler that 

 the vitreous body is an amorphous, gelatinous mass, the product of a 

 process of transudation from the blood vessels (page 81). Its 

 fibrous structure is so uniform, regular, and constant in all sections, 

 whatever method is used in their preparation, that we can not regard 

 the vitreous body as an amorphous mass. To dispose of the fibers as 

 artificial productions of the reagents used in the preparation of the 

 material, would be to do violence to fact. 



By a careful study of the vitreous body in the sheep 's eye, Van 

 Pee arrives at the conclusion, that the radial fibers are, indeed, of 

 retinal or ectodermal origin, but that the more prominent parallel 

 fibers, which constitute the bulk of the vitreous body, are mesodermal 

 in their origin, arising from the mesenchyme between the optic cup 

 and the body wall. These fibers then pass through the narrow peri- 

 lenticular opening and form the major part of the vitreous body. 

 It is true, as will be seen from figure 2, that at a later stage of 

 development numerous mesoderm cells with long protoplasmic out- 

 growths enter into the vitreous body, and the significance of this 

 formation will be considered in its place, but it is equally true, that 

 in the earlier stages, which are under consideration here, and which 

 show the vitreous body in its primitive and simplest form, both the 

 radial and the parallel fibers are exclusively the product of the basal 

 cells of the retina and lens. In the eye of the pig, mesodermal 

 vitreous fibers are hot found at this stage of development. 



Lenhossek, in a lengthy monograph, attempts to demonstrate 

 that all the fibers constituting the structural parts of the vitreous 

 body, are the product of the basal cells of the lens, and that the 

 retina has no share in their production. All our preparations show 

 the lenticular fibers first described by v. Lenhossek and later by his 

 pupil, v. Szily. They are especially prominent in embryos of 10 

 and 11 mm length, radiating from all parts of the lens, and enter- 

 ing into communication with the retinal fibers, the extra-ocular 

 mesoderm, and even with the body ectoderm. But we can not regard 

 them as the exclusive structural parts of the vitreous body. It is 



