. Diseases & disorders of the horse : a treatise on equine medicine and surgery. Horses; Horses -- Diseases; Horse Diseases. 96 A nerve-fibre is a microscopic element composed of a proper wall anct contents. The wall is the sheath we mentioned, and it is a thin elastic membrane. The contents comprise in the centre a solid core, called the axis cylinder, along which the nerve current passes. In many fibres, between the axis cylinder and the wall, is found a viscid substance called the medulla. Those fibres which do not contain the medulla, and which are specially characteristic of the sympa
. Diseases & disorders of the horse : a treatise on equine medicine and surgery. Horses; Horses -- Diseases; Horse Diseases. 96 A nerve-fibre is a microscopic element composed of a proper wall anct contents. The wall is the sheath we mentioned, and it is a thin elastic membrane. The contents comprise in the centre a solid core, called the axis cylinder, along which the nerve current passes. In many fibres, between the axis cylinder and the wall, is found a viscid substance called the medulla. Those fibres which do not contain the medulla, and which are specially characteristic of the sympathetic system, are called non-medullated. The majority of nerve-fibres measure about ^^ of an inch in diameter,. The nerve-cells are large nucleated bodies of very variable shape, and they have one or more prolongations extending from them. These prolongations or poles establish relations with the nerve-fibres, and constitute the origin of the In the above figures, A shows some nerve cells of dilTerent shapes. I> shows a stellate cell from a developing animal, magnified 400 diameters. When a cerebro-spinal nerve is irritated by pinching, there is either pain manifested, or there is twitching of one or more muscles, to which the nerve distributes its fibres. From various considerations, it is certain that pain is- always the result of change in the nerve cells of the brain. Therefore, in such experiments as those referred to, it seems to the experimenter that the irritation of the nerve-fibre is conducted in one of two directions, either ta the brain the central termination of the fibre, when there is pain, or to a muscle when there is movement. The effects of these simple experiments arc the types of what always occur, when nerve-fibres are engaged in the performance of their functions (Kirke). The brain of the horse and of the other higher animals is formed of a central white part composed of fibres, and an outer convoluted portion of grey matter composed of nerve-
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