. Cunningham's Text-book of anatomy. Anatomy. NEUKOGLIA. 511 morphological difference between a dendrite and an axon disappears, and van Gehuchten's functional distinction alone remains characteristic, viz., that the axon is cellulifugal and conducts impulses away from the cell, whilst the dendrites are cellulipetal and conduct impulses towards the cell. It is, however, more in accordance with the facts to regard the sensory neurones as genetically quite distinct from the rest of the nervous system (see p. -±98). Neuroglia.—The neuroglia is the supporting tissue of the cerebro-spinal axis. It
. Cunningham's Text-book of anatomy. Anatomy. NEUKOGLIA. 511 morphological difference between a dendrite and an axon disappears, and van Gehuchten's functional distinction alone remains characteristic, viz., that the axon is cellulifugal and conducts impulses away from the cell, whilst the dendrites are cellulipetal and conduct impulses towards the cell. It is, however, more in accordance with the facts to regard the sensory neurones as genetically quite distinct from the rest of the nervous system (see p. -±98). Neuroglia.—The neuroglia is the supporting tissue of the cerebro-spinal axis. It may be considered to include two different forms of tissue, viz., the lining ependymal cells and the neuroglia proper. We place these under the one heading, seeing that they have a common developmental origin. The ependymal cells are the columnar epithelial cells which line the central canal of the spinal medulla and the ventricles of the brain. In the embryonic con- dition a process from the deep extremity of each cell, traverses the entire thickness of the neural wall, and reaches the surface. It is not known whether this process exists in the adult. The neuroglia proper is present in both the white and the gray matter of the cerebro-spinal axis. It constitutes an all- pervading basis substance, in which the various nerve elements are embedded in such a way that they are all bound together into a consistent mass, and are yet all severally isolated from each other. Neuroglia consists of cells and fine filaments. The fibrils are present in enormous numbers, and by their interlacements they constitute what appears to be a fine feltwork. At the points where the fibrils intercross may be seen the flattened glial cells. Whilst the neuroglia is for the most part intimately intermixed with the nerve elements, there are, in both brain and spinal medulla, certain localities where it is spread out in more or less pure layers. Thus, upon the surface of the .brain and of the spinal med
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