The transmission of impulses through the ciliary ganglion

THE transmission of impulses through the ganglia of the sympathetic chain has recently been studied by Bishop & Heinbecker [1932], Brown [1934], Fischer & Lowenbach [1933], Bronk et al. [1935], Eccles [1935 a, b, c], and Obrador & Odoriz [1936]. Of the parasympathetic system, the ciliary ganglion has been chosen for study as it is accessible, compact and comparatively large. Langley & Anderson [1892] inferred from the paralysis produced by nicotine that the ganglion is a relay station in the pupil constrictor tract. This was confirmed by the investigation of the effect of asphyxia by Langendorff [1894], and by the degeneration experiments of Apolant [1896]. Accounts of the anatomy of the ganglion and its roots have been given by Jegorow [1886] and Christensen [1936]. These authors are agreed that in the cat the ciliary ganglion has a motor root, but no macroscopic sensory or sympathetic roots. However, some sensory fibres reach the ganglion from the nasociliary nerve via a communicating branch to the lateral short ciliary nerve. These fibres form Jegorow's " long root ". Attempts to demonstrate a sympathetic root microscopically have been unsuccessful [Apolant, 1896; Christensen, 1936], although chromatolytic changes in the ciliary ganglion after removal of the superior cervical ganglion have been described [Fritz, 1899]. It has been suggested by Mazzantini [1927] and by Muller [1931] that the ganglion acts as co-ordinating centre for pupil dilator and constrictor impulses. The earlier work on the histology of the ganglion is reviewed by Muller & Dahl [1910]. Its structure has been reinvestigated by Beauvieux & Dupas [1926], Pines [1927], Pines & Friedman [1929] and Slavich L1932]. Pines reaffirms that the ciliary ganglion of