OX VITREOUS HUMOUR. 1. THE RESIDUAL PROTEIN

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Abstract
The ox vitreous humor consists of 2 parts, a hyaluronic acid and protein jelly and an insoluble residue. This residue is obtained by Suspending fresh vitreous in various baths of saline under conditions of refrigeration until diffusion of the soluble substances is complete. Part of the residue is transformed into a soluble prepn. to facilitate its further study. The residue is arranged as a fine meshwork or fibers and is partly anisotropic. It is of considerable tensile strength. It is practically identical with collagen derived from the ox cornea although collagen lacks such high tensile strength. For example, they are both composed of: N2 = 15.3% (for residue) = 16% (for collagen), carbohydrate = 6%, amino acids proline, hydroxy-proline, glycine, glutamic acid, aspartic acid and alanine as shown by the amino acid chromatogram. They do not contain hexosamine. They are dissolved by pepsin but not by trypsin. They are liquified by collagenase derived from Clostridium welchii. They have similar X-ray appearances. But a collagen fiber shows maximal swelling in acid, minimal swelling in neutral and intermediate swelling in alkaline solns., whereas the vitreous shows the reverse, changes being of maximum size at neutrality. This inconsistency is, however, only apparent. When a collagen fiber swells it shortens, thus when collagen fibers are arranged in a network, as they are in the vitreous, swelling of the individual fibers is associated with contraction of the mass due to the shortening process. Salts which lessen the acid or alkaline swelling of gelatin similarly lessen the shrinkage of the vitreous residue. The degree of depression depends on the valency of the anion when an acid medium is being considered, and of the cation when the medium is alkaline.

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