Note 176 — Chapter VII · THE ELEMENTARY STRUCTURE OF THE NERVOUS SYSTEM.

Ranvier, in the Comptes Rendus, 1875, Vol. LXXXI. p. 1276. This observation throws light on the fact that cell processes are sometimes seen entering nerve-roots (§ 124).

The very remarkable observations of Mr. F. Balfour, On the Development of the Spinal Nerves in Elasmobranch Fishes (Philos. Trans., Vol. CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk arise from histological changes in a mass of cells at first all alike; not that ganglion-cells are formed and from their processes elongate into fibres. The nerve, he says, forms a continuation of its root rather than of its ganglion (p. 181); which accords with Ranvier’s view.