. A treatise on nervous and mental diseases, for students and practitioners of medicine. 8. In Fig. 42 is seen a drawing from a photo-micrograph, madefor me by Dr. Henry McDonald, of these same anterior horn cellsas observed under the microscope, magnified 360 times. It gives aclear idea of the way in which they lie in the meshes of the con-nective tissue, with their processes reaching out in different direc-tions, and surroimded by their peri-cellular spaces. Since we have become in a measure acquainted with the structureof the spinal cord, we shall see how the nerve fibres run from theanteri
. A treatise on nervous and mental diseases, for students and practitioners of medicine. 8. In Fig. 42 is seen a drawing from a photo-micrograph, madefor me by Dr. Henry McDonald, of these same anterior horn cellsas observed under the microscope, magnified 360 times. It gives aclear idea of the way in which they lie in the meshes of the con-nective tissue, with their processes reaching out in different direc-tions, and surroimded by their peri-cellular spaces. Since we have become in a measure acquainted with the structureof the spinal cord, we shall see how the nerve fibres run from theanterior and posterior roots. At first we shall occupy ourselves withthe motor or anterior nerve roots. These fibres pass through the 60 IlSrTRODUCTORY. antero-lateral column, spreading out widely. They then enter theanterior horns, passing to the ganglion cell through the axis-cylinderprocess, a few passing to the cells of the opposite anterior hornthrough the anterior commissure. From these anterior horn cellsthe fibres pass to the anterior and lateral pyramidal columns—to the Fig. Drawing of cells from the anterior horns of the spinal cord. Obtained by tappingthe fresh cord of an ox. former along the bottom of the anterior median fissure, to the latterin a way that is as yet a matter of conjecture. The fibres from theposterior or sensory nerve roots enter the cord, first going to theganglion upon the posterior root, which innervates these posteriorroot fibres in the same way in which the anterior horn cellsinnervate the anterior nerve root fibres. Thus, as we shall see instudying myelitis of the anterior horns, a degeneration of these ante- ANATOMY. 61 rior horn cells causes degenerative changes in the anterior nerve rootfibres. In the same way, section or disease of the ganghon uponthe posterior root causes degeneration of the peripheral nerve fibres Fig. 42.
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