. The development of the chick; an introduction to embryology . Fig. 141. — Transverse section through the spinalcord of a 9-day chick, prepared by the methodof Golgi. (After Ramon y Cajal.)Col., Collaterals, d. R., Dorsal root. G., Gray matter. Gn., Ganglion. Nbl. 4, Neuroblast of the ventral horn (motor), v. R., Ventral root. W., White matter. In the course of the later development the cell-body movesto one side so that the central and peripheral branches appearnearly continuous (Fig. 141). Farther shifting of the cell-bodyproduces the characteristic form of the ganglionic nerve-cell withrou
. The development of the chick; an introduction to embryology . Fig. 141. — Transverse section through the spinalcord of a 9-day chick, prepared by the methodof Golgi. (After Ramon y Cajal.)Col., Collaterals, d. R., Dorsal root. G., Gray matter. Gn., Ganglion. Nbl. 4, Neuroblast of the ventral horn (motor), v. R., Ventral root. W., White matter. In the course of the later development the cell-body movesto one side so that the central and peripheral branches appearnearly continuous (Fig. 141). Farther shifting of the cell-bodyproduces the characteristic form of the ganglionic nerve-cell withrounded body provided with stem from which the central andperipheral branches pass off in opposite directions. The centralprocess enters the marginal velum near its dorsal boundary and 238 THE DEVELOPMENT OF THE CHICK there bifurcates, producing two branches, one of which growstowards the head and the other towards the tail in the dorsal Fig. 142. — Six centripetal axones of the dorsal root, rigorously copied from a good preparation prepared according to the method of Golgi. From a longitudinal and tangential section of the dorsal column of the spinal cord of an 8- day chick. (After Ramon y Cajal.) Col., Collaterals. 1, 2, 3, 4, 5, 6, the axonesentering the cord. column of the white matter. The ascending and descendingbranches send off lateral branches, collaterals, which pass deeperinto the cord, and ramify in the gray matter of the dorsal horn. THE NERVOUS SYSTEM 239 Fig. 142 represents six central processes of ganglionic neuroblastsentering the cord and branching as described. After this preliminary account of the neuroblasts we maytake up the development of the spinal cord, brain, and peripheralnervous system. II. The Development of the Spinal Cord We have seen that the epithelial cells of the neural tubestretch from the lumen of the central canal to the exterior, andthat the nuclei are arranged so as to leave t
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