. A text-book of human physiology . With regard to the further connection ofthe two kinds of fibers we distinguish: (1) asecondary efferent path; (2) a secondary affer-ent path; and (3) the paths by which afferentpass over into efferent imi)ulses. Those tracts which connect the nerve cellsof the anterior horn with the higher centerswe designate as secondary efferent paths. Theyare the paths by which impulses liberated in thecells of the higher centers are conveyed to themotor cells of the anterior horn. The fibers entering the cord from the spinalganglia are brought into relation with the cell
. A text-book of human physiology . With regard to the further connection ofthe two kinds of fibers we distinguish: (1) asecondary efferent path; (2) a secondary affer-ent path; and (3) the paths by which afferentpass over into efferent imi)ulses. Those tracts which connect the nerve cellsof the anterior horn with the higher centerswe designate as secondary efferent paths. Theyare the paths by which impulses liberated in thecells of the higher centers are conveyed to themotor cells of the anterior horn. The fibers entering the cord from the spinalganglia are brought into relation with the cells of the posterior horn whoseaxis-cylinder processes constitute the secondary afferent paths. It is by thesepaths that impulses are transmitted to the higher centers. The transition from afferent to efferent i)aths may occur in several simplest instance is when an afferent nerve fiber or one of its collateralsconnects directly with the motor cell of an efferent nerve fiber or with some ofits processes by means of Fig. —Schema, after Kollikerand Leiihoss6k. A, motor cellswith root fibers; B, spinal ganglioncell with its processes; C, a sen-sory collateral; D, column cell withT-shaped branching processes; E,collaterals of the same. 564 PHYSIOLOGY OF THE NERVE CELL AND THE SPINAL CORD Again a nerve cell with its processes, etc., may be intercalated as a new ele-ment between two primary paths, as shown in the schema (Fig. 255) based onthe neuron theorj. The terminal libers of an afferent nerve fiber (B) or itscollaterals (C) unite with a nerve cell (column cell) somewhere in the centralnervous system (D). This cell sends foi-th an axis-cylinder process which hasseveral collaterals (E) and these in turn serve to bring it into contact withan anterior horn cell (A). By this arrangement it is evident that an impulsecoming via a single afferent fiber is transmitted to a large number of efferentfibers. If now we imagine one or more such cells interposed between
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