A spreading cerebral elema may be produced by local freeze-injtıry of tlhe brain. This type of edena resembles that seen in tnan after focal lorain dannage anl proviles a convenient experimental model for studying this problet. Cere-brul edenu: after freeze-injury litis been extensively studied at tlhe light micro-scopic level by IKlatzo and his: ssociats (1–1). After an intravenous injection of albumin labelel with fluorescing compounds or radioisotopes, the tracer protein passel into the lorain only in the area of injury. The labeled allumin tlın tnigritel from the site of injury concotnittııt with the spreid of cleını. The levelopment of a satisfactory lhistoelhemical procedure for lhorseradish peroxidase (5-6) has małe possible its use as a protein traver for electron mieroscopy. This metluol lı: s provedl very tseful in tıltrustructural stulics of the novement of protein between tihe viscular und extracellular spaces of verious tisstes including tlhe brain. łtese, lrightınan. Becker. Hirano and otlhers (7–13) lı: ve slıown that lıorseradislı peroxilase given intravenously lid not pass the intact vascular endotlheliunn of tlıe brain.(ln tlie other lıand, if the trarer was introluced into the ventriels, sular: chnoid spatce or lirectly into the brain subst: unre it enterel undi ınovel freely tlhrough the extracellular space of rortex end white mitter.

In the study reportel here, experimental cerebral edena was produccd by means of a cerebral frecze-injury. The ultrastructural clanges associated with passage of plasma protein across the capillary wall were studiel using intravenous lhorseralish peroxilase. The location of this exogenous plasma protein in the cerebral neuropil. its manner of spread and its relationship to the various