3. AUTONOMIC NERVOUS SYSTEMS
115
1. OCULOMOTOR NERVE
Oculomotor nerves are absent from forms with reduced eyes, but
where present they supply preganglionic fibers to the ciliary ganglion,
from which postganglionic fibers pass to the eyeball (Fig. 2). Stimulation of the oculomotor nerves causes pupillary dilatation in the teleost
Uranoscopus scaber (Young, 1931a) and in one selachian, Scyllium,
although this was not seen in two others (Mustelus, Trygon; Young,
1933a). This response is in marked contrast to the pupillary constriction
dil.
Fig. 2. Diagram of a ventral view of the anterior sympathetic system in Uratioscoprrs, showing the sympathetic and parasympathetic innervation of the iris. cil. gn.,
ciliary ganglion; dil., pupil dilator muscle; n. splanch., anterior splanchnic nerve; sph.,
pupil sphincter muscle; sp. 1, first spinal nerve; cranial nerves numbered 11, 111,
IV, V, VIL, IX, and X. ( . . . ) Sympathetic pathways and ( - - - ) parasympathetic
path\\.ays; positions of ganglionic synapses shown by filled circles. Redrawn, slightly
modified, from Fig. 1 of Young (1931a).