366 HISTOLOGY. 



form, constitute a dense mass, the nucleus of the lens. The outer fibers 

 of the cortical substance are softer. They have smooth borders, and nuclei 

 which are chiefly in the equatorial plane. Their protoplasm is transformed 

 into a clear fluid substance, said to be chiefly a globulin. The fibers are 

 united to one another by a small amount of cement substance, which is 

 more abundant at the poles; after maceration of the lens it generally radiates 

 from either pole, forming a stellate figure around each. These have three 

 rays in older embryos and ordinarily nine rays in the adult. The lens 

 fibers all run in the meridional direction from the anterior stellate rays to 

 the posterior. The nearer the anterior pole they arise, the further 

 from the posterior pole they terminate, and vice versa, since no fiber is 

 long enough to extend from one pole to the other. The fibers of the cor- 

 tical substance are said to form about 2000 radial lamellae comparable 

 with the segments of an orange. Owing to the differences in consistency 

 of fibers of various ages, concentric lamellae may be separated in hardened 

 lenses. 



VITREOUS BODY. 



The corpus vitreum consists of the fluid vitreous humor and loose 

 fibrous strands of stroma. Although some recent pathological cases sug- 

 gest that the latter are arranged like the septa of an orange, it has not been 

 established that they have any definite arrangement. The cells of the 

 vitreous body are round forms, probably leucocytes, and stellate or spindle 

 shaped forms representing the connective tissue which invaded the vitreous 

 body with the blood vessels. The latter have atrophied and been resorbed. 

 Opaque flakes which occur normally and float into the field of vision 

 as "muscae volitantes," have been ascribed to fragments of degenerated 

 tissue; vascuolated degenerating cells have been observed. Crystals 

 may form and settle in the lower part of the bulb. The vitreous body is 

 bounded by a very resistant thick fibrous layer which does not justify the 

 term hyaloid membrane. 



TUNICA VASCULOSA. 



Chorioid. Between the sclera and the chorioid there is a loose tissue 

 containing many elastic fibers and branched pigment cells, together with 

 flat non-pigmented cells. In separating the sclera from the chorioid this , 

 layer is divided into the lamina fusca of the sclera and the lamina supra- 

 chorioidea. Internal to the latter is the lamina vasculosa which forms the 

 greater part of the chorioid. It contains many large blood vessels imbedded 

 in a loose elastic connective tissue, some of its cells being branched and 

 pigmented ; others without pigment are flat and arranged in layers surround- 



