The Presence of a Barrier Between the Bloodstream and the Brain

Multiple Choice

The presence of a barrier between the bloodstream and the brain is suggested by the observation that

A) all cells of the body are stained by a dye injected into the bloodstream.
B) injection of dye into the bloodstream stains all cells but those of the brain and spinal cord.
C) the gut is stained by a dye injected into the brain ventricles.
D) injection of dye into the spinal cord stains the cells of the gut.
E) injection of dye into the gut stains the cells of the spinal cord.