Dr. Gierke, of Breslau, has, in two articles in the “Neurologisches Centralblatt” (Numbers 16 and 17, 1883), given the results of special researches on the neuroglia. He accuses Deiters, Boll, Golgi, and Jastrowitz of making incorrect descriptions, and of mistaking the results of their own reagents and dyes for natural structures. Gierki promises to publish his researches at greater length with illustrations, which are highly necessary in the description of delicate tissues. In the meantime he gives a number of details which could only be fairly reproduced by translating his papers. The neuroglia is the supporting tissue or frame-work of the nervous centres. It forms one-third of the substance of the grey matter, and its cells throw out branching processes which, taking the shape of flattened fibres, form sheaths for the nerve tubes. These never lie against one another, as Boll imagined. The cells of the neuroglia in the spinal cord of the sheep have a diameter of from 0·005 to 0·008 mm., and their processes are sometimes as long as from 0·4 to 0·2 mm. The neuroglia is everywhere, save at a part of the medulla oblongata, where the nerve tubes of the stratum zonale Arnoldi crowd upon one another, and lie directly under the pia mater. In other places, as in the substantia gelatinosa Rolandi, the neuroglia prevails, and there are few nerve elements. In contradiction to those who hold that the perivascular spaces may be owing to retraction of the dead tissues or contraction of vessels, Dr. Gierke maintains that there is not the slightest doubt that the perivascular spaces exist in the living brain. They are of varying calibre, and their strongly developed cellular ramifications are analogous to the sinuses in the lymphatic gland. In some places, as in the central canal of the spinal cord, he has found the large vessels surrounded by perivascular canals, which he has traced into real lymphatics.
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