The mucopolysaccharides of the ground substance of the human brain.

The concept of the presence of mucopolysaccharides forming an interstitial ground substance in central nervous tissues is revived. The biochemical reports of both neutral and acid mucopolysaccharides in both gray and white matter of the normal brain are reviewed. The earlier histochemical reports and the histochemical studies in this laboratory are appraised and are thought to demonstrate the presence of neutral mucopolysaccharides in both gray and white matter, more evident in the former. These mucopolysaccharides are thought somewhat greater in the arcuate white matter than in the deeper white matter and greater in the striae of white matter coursing through the corpus striatum than in the internal capsule. The presence of acid mucopolysaccharides in normal brain substance is not clearly demonstrated histochemically, though they have been noted in some oligodendrogliomas and in rare well differentiated astrocytomas. The possibility is suggested that acid mucopolysaccharides are present, as the biochemical studies indicate, but that their acid groups are normally blocked or otherwise rendered non-reactive, preventing their histochemical disclosure in normal tissues but serving as a source of those seen in pathologic conditions. The concept of a ground substance has important implications for the understanding of the distribution of excellular fluid in brain tissues in both the normal state and in edema.