In carcinoma of the brain the parenchyma of the invaded portions appears to be replaced by more or less dense masses of carcinoma cells grouped around distended blood vessels, or it may remain in the form of islets surrounded by strands of cancer tissue. Buchholz,1 Gallavardin and Varay2 assert that the brain tissue is not actually destroyed but is merely "pushed aside" by the tumor mass within it ("eingesprengt") without provoking reactive phenomena. They say the glia may show proliferation in the immediate neighborhood of the tumor, but the mesodermic tissues—blood vessels and pia—show no reaction. De Fano3 also emphasizes the absence of mesodermic reaction in carcinoma produced experimentally by transplantation in the brains of mice and rats. Only in animals "partially immune" did he find plasma cells or lymphocytes and "the nerve elements, the ganglion cells, undergoing atrophy." "Lasting proliferation of neuroglia seems," he says, "to