Recent Studies of the Morphology of the Neurone in Health and Disease

Abstract

Normal Neurone THE modern conception of the structure of the neurone is founded mainly on the work of Cajal and of Nissl. Earlier observers, such as Waller, His, and Ranvier, had established the connection of the axone with the nerve cell and paved the way for the neurone theory, which was formulated almost in its present form by Cajal (1891) on the basis of purely morphological study. To his method of impregnation with reduced silver nitrate we owe our knowledge of the neurofibrillar structure of the neurone and of its reactions to injury or disease. Modern knowledge of the changes in the structure of the nerve cell in disease is, however, chiefly based on Nissl's studies by his polychrome methylene blue method. His classification stands to-day with minor modifications as the basis of neuronal pathology. The end of the life-work of Nissl and Cajal, therefore, forms a convenient starting-point for a survey of recent studies on the morphology of the neurone. It will be convenient first to examine the normal structure of the neurone as indicated by these researches, and secondly to review additions to knowledge of the changes which the neurone undergoes in disease.THE PERIKARYON Physical Constitution.-The examination of the fresh nerve cell with the ultra-microscope by Marinesco (1911) and Mott (1912) did not reveal any constituents which other methods had not shown. Rather, it made them cast doubts on the existence of Nissl granules and neurofibrils in a preformed state. It seemed to them that these structures could not be brought out without special staining technique and were to that extent artefacts. To-day, however,