Abstract
The impact of electron microscopy on our concepts of neurophysiology and neurochemistry already has been far reaching. In particular has this been true in the areas of extracellular space, water transport, blood-brain barrier, neurosecretion and synaptic transmission. Its contributions in the field of neoplasia are so recent and so scant that one can only conjecture that the correlation of abnormal structure with abnormal function can be carried over into the cytochemical analysis of the lesions; and that electron microscopy will offer a technic for studying the site of action of the cytotoxic agents.