For some years past the leading authorities have been generally agreed that the neuroglia is a tissue composed exclusively of special cells and their processes. Ramon y Cajal, for example, describes it as consisting of small cells provided with very fine, wavy, and only slightly ramified processes, which, after a variable course, terminate freely or attach themselves to the surface of the capillaries. From observations made with the aid of a new method, Professor Weigert, of Frankfurt, has arrived at a theory regarding the constitution of the neuroglia which is diametrically opposed to this now generally accepted view. He published a preliminary note on the subject in 1890, but it was only a year ago that he gave a full account of his researches, together with a description of an important improvement in his method. This improved method, in which methyl violet is the staining agent employed, is one that is exceedingly complicated and troublesome to carry out. It gives preparations in which the neuroglia-fibres and the nuclei of the neuroglia-cells are stained violet, while the protoplasm of the cells remains unstained and invisible. The reaction succeeds only in the human subject, and, as a rule, only with tissues that are moderately fresh. The results that he has obtained with this method have led Weigert to advocate the view that the neuroglia-fibres, which have hitherto been regarded as processes of the Deiters' cells, are chemically distinct, and morphologically separate, from the cell-protoplasm; in other words that the fibres which are stained violet in his preparations are not processes of the cells, but are completely differentiated from them. It is clear that we cannot rightly understand the nature of the pathological changes that occur in the neuroglia until this question of the structure of the normal tissue is settled in our minds. Weigert's theory is certain to give rise to a large amount of discussion in the near future. I wish now to offer merely a small contribution to that discussion. I have for some weeks been working with Weigert's method in the course of a study of the normal histology and pathological anatomy of the neuroglia. Already I feel convinced in my own mind that Weigert has been led into an error by certain fallacious appearances produced by his method, and that the older view of the structure of the neuroglia is the correct one.