Behaviour of Bielschowsky-stained Neurofibrillæ between Crossed Nicols

Abstract

ARTIFICIAL cultivation of tissues in vitro has little affected the field of investigation in organic neurology. The older histological methods are still irreplaceable, and of special value is that of Bielschowsky, which renders distinguishable the minute neurofibrillæ at all stages of development save possibly the earliest at which nervous conducting structures are present. Bielschowsky's method involves the staining of the fibrillæ probably with a complex compound of silver formed through the interaction of certain of its salts in solution with the chemical constituents left in the nerve after treatment with a series of ‘fixative’ reagents. At least, that is a possible explanation of the visible results viewed through the microscope. The colour of the fibrillæ varies from a dark to a very dark brown or black, and unfortunately non-nervous structures are also coloured a lighter brown or yellow, so that the actual identification of the fibrillæ is in practice inferred from their visible form and connexions as well as from their appearance more or less sharply contrasted with their immediate surroundings.