. Cunningham's Text-book of anatomy. Anatomy. 532 THE NEEVOUS SYSTEM. to form an irregular and very imperfect fibrous framework of support. The neuroglia is disposed in a layer of varyiug thickness around the medulla, subjacent to the pia mater, and is carried into the medulla so as to give a coating to both sides of the various pial septa. The neuroglia is disposed also around the various nerve-fibres, so that each of these may be said to lie in a canal or tunnel of this substance. The nerve-fibres are all medullated, but they are not provided with primitive sheaths. It is the medullary subst
. Cunningham's Text-book of anatomy. Anatomy. 532 THE NEEVOUS SYSTEM. to form an irregular and very imperfect fibrous framework of support. The neuroglia is disposed in a layer of varyiug thickness around the medulla, subjacent to the pia mater, and is carried into the medulla so as to give a coating to both sides of the various pial septa. The neuroglia is disposed also around the various nerve-fibres, so that each of these may be said to lie in a canal or tunnel of this substance. The nerve-fibres are all medullated, but they are not provided with primitive sheaths. It is the medullary substance of the nerve-fibres which gives to the white matter its opaque, milky-white appearance. When a thin transverse section of the medulla is .stained in carmine and examined under the microscope the white matter presents the appearance of a series of closely applied circles, each with a dot in the centre. The dot is the transversely divided axis-cylinder of a nerve-fibre, and the dark ring which forms the circumference of the circle represents the wall of the neuroglial canal which is occupied by the fibre. The medullary substance is very faintly seen. It presents a filmy or cloudy appearance between the axis-cylinder and the neuroglial ring. Arrangement of the Nerve-fibres of the White Matter in Fasciculi or Tracts.—When the white matter of a healthy adult spinal medulla is examined, the fibres which compose it are seen to vary consider- ably in point of size; and although there are special places where large fibres—or it may be small fibres —are present in greater numbers than elsewhere, yet, as a rule, both great and small fibres are mixed up together. No conclusive evidence can be obtained in such a medulla, by any means at our disposal, of the fact that the longitudinally arranged fibres are grouped together in more or less definite tracts or fasciculi, the fibres of which run a definite course and present definite connexions. Yet this is known to be the case, and t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
