Publisher Summary This chapter analyzes possible histological basis of inhibition. Histological evidence, on the whole, supports the notion that inhibition requires specific inhibitory neurons. There are many histological reasons to assume that most of the specific inhibitory neurons either have relatively short axons or are even of Golgi's type XI. It is remarkable that all specific inhibitory neurons hitherto identified are short ones that, in general, bridge distances of a few millimeters. This offers some clues for the investigation of these neurons by histological means—by cutting all important extraneous connections of certain parts of the gray matter—a goal achieved, for example, by isolating slabs of nervous tissue from the remaining parts of the central nervous system (CNS) but leaving intact their blood supply, all nervous elements that originate outside can be brought to degeneration. In such isolated slabs, nerve cells and their synaptic connections can survive indefinitely, and after about two months of survival time, all nervous elements encountered intact, particularly synapses, may safely be considered as originating from neurons that have survived in the slab. This procedure is, therefore, suited to separate from a large number of synapses normally present those that belong to short neurons or short connections.