VII. 20 



AUTONOMIC NERVES OF TELEOSTS 



223 



that nerve, this ramus carrying post-ganglionic fibres to the skin. 

 Some of these fibres control the melanophores, causing them to 

 contract (p. 259). In elasmobranchs there are no grey rami communi- 

 cantes and no sympathetic system in the head (p. 173); the differences 

 between the two groups are therefore very striking. 



HI prof Viymp 



Fig. 139. Diagram of the autonomic nervous system of Uranoscopus seen from the side. 



bl. mesonephric bladder; cil.gn. ciliary ganglion; dors, dorsal root; n.sph. nerve to anal 

 sphincter; n.spl. splanchnic nerve; prof, nervus ophthalmicus profundus; rad. brev. short 

 root of ciliary ganglion; r.comm. ramus communicans (including both white and grey fibres); 

 stan. 'corpuscle of Stannius' (adrenal cortical tissue?); ventr. ventral root; ///, oculomotor 

 nerve; V— X symp. sympathetic ganglia associated with the cranial nerves. (From Young, 



Quart. J. Micr. Sci. 75.) 



Fig. 140. Tracing of the contractions of a strip of the stomach muscle of the angler- 

 fish, Lophins, attached to a lever. Time in minutes. At A, faradic stimulation of the 

 vagus nerve. Drugs then added to the solution to make, at B acetyl choline 1/1,000,000; 

 at c acetyl choline 1/100,000; at D adrenaline 1/100,000. 

 (From Young, Proc. Roy. Soc. 120.) 



Little is known about the parasympathetic system of bony fishes. 

 The oculomotor nerve carries fibres to the iris, which work in the 

 opposite direction to fibres from the sympathetic (p. 214). There is 

 also a well-developed vagal system, but so far as is known no para- 

 sympathetic fibres in other cranial nerves and probably no sacral 

 parasympathetic system. Electrical stimulation of the vagus nerve 



