A positive periodic acid-Schiff reaction occurs between the cell bodies in the gray matter of the adult central nervous system. Since this reaction is not exhibited by neuroglia fibers, nerve processes, or cell bodies, it has been suggested that there is an additional element in the central nervous system, the ground substance, which is probably of a carbohydrate-protein nature (Hess,5 1953). Trypan blue, administered intravenously or intraperitoneally, is a valid test substance for the presence or absence of a blood-brain barrier (King,10 1939). Intravenous trypan blue does not stain the adult brain (Goldmann,4 1913), indicating the presence of a blood-brain barrier. On the other hand, intravenous trypan blue stains the brains of several newborn animals (Behnsen,1 1927; Stern and Peyrot,15 1927; Penta,* 1932), indicating the absence of a blood-brain barrier. The mouse brain stains easily and extensively with trypan blue until 2 weeks of age,
HESS A. Blood-Brain Barrier and Ground Substance of Central Nervous System: Effect of Brain Wounds. AMA Arch NeurPsych. 1955;74(2):149–157. doi:10.1001/archneurpsyc.1955.02330140033006
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