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From pepsin-solubilized vitreous body collagen three different precipitates were collected by differential salt precipitation. These three different protein fractions contain hydroxyproline and show different patterns in poly-acrylamide gel electrophoresis suggesting different collagen types.

Some proteolytic enzymes were examined for zonulolytic activity. Thermolysin, proteinase K, and pronase E are more reactive in zonulolysis than trypsin. At present no definitive statement is possible about the destructive reaction of these enzymes on the other tissues of the eye.

The course of zonular fibers in the area of pars plicata corporis ciliaris could be shown down to the pigmented epithelial layer and its basement membrane. Single fibrils enter in a connection with the plasma membrane in all investigated parts. Fibrils could be observed in the cytoplasm of the ora serrata. For the other areas (pars plicata corporis ciliaris, pars plana) this can be suggested too.

By our investigations we found identity of collagen and zonula fibers protein. In Disk-electrophoresis both the zonula fibers and the fibers of the vitreous show the a-component only. Therefore it is likely that these proteins are closely related.

Characteristically stained polyacrylamide gels can be obtained by disk-electrophoresis in acid medium of several tissues of the bovine eye. The technique permits to prove different types of collagen in the eye, and allows the differentiation and identification of the tissues. By these results the different tissues of the eye can be divided into three groups.1.Tissues showing two a collagen components in polyacrylamide gel (cornea, sclera, iris, ciliary body, anterior lens capsule, and the pigmented epithelium of the retina).2.Tissues possessing one a component only (zonula fiber and vitreous body).3.Tissues which show neither the a nor the ß and ? component of collagen (lens nucleous and retina without pigmented epithelium).

Three areas in which zonular fibers of Zinn enter were demonstrated with the aid of scanning electron microscopy.1.The area, which applied to the edge of the lens.2.The area of Pars plicata corporis ciliaris.3.The area of Pars plana.

Some proteases, i.e. trypsin, a-chymotrypsin, thermolysin, proteinase K, a-amylase, collagenase, and papain were investigated on their effect on isolated zonular fibers. All these enzymes but collagenase were zonulolytic active. An attack on the ground substance of the fibers by substances solving glycosaminoglycans and proteoglycans (hyaluronidase, EDTA, guanidinium chloride, H2O2) showed an increased effect of the enzymes used. These results suggest that the interfibrillar matrix has a protective function on the zonular fibers.

We were able to confirm experimentally the finding of Hofmann and Lembeck, i.e. that zonulolysis is dependent on tension of the fibres. A better zonulolytic effect is caused in our opinion both by exposure of the fibres and by enlargement of the substrate surface.