332 THE NERVOUS SYSTEM 



All the fibres which convey impulses to the skin end 

 in the ganglia of the lateral chain. Here post-gangUonic 

 fibres (grey rami communicantes) arise and join the seg 

 mental somatic nerves. It follows, therefore, that in the 

 thoracico-lumbar region each spinal nerve has a white 

 ramus leaving it and a grey ramus joining it. In seg- 

 ments of the body from which the sympathetic does not 

 arise only a grey ramus, derived from another segment, 

 is present (Fig. 61). 



The detailed distribution and action of the sympathetic 

 is shown in the Table given on p. 333. 



Cranial Autonomic 



Third Nerve. — The visceral fibres have their cell-station 

 in the cihary ganglia. They are motor to the sphincter 

 pupillse and cihary muscles. 



Seventh Nerve.— The visceral branch is the chorda 

 tympani which supphes secretory and vaso-dilator fibres 

 to the submaxillary and subhngual glands. The cell- 

 stations for the subungual gland are in the submaxillary 

 ganglia, and those for the submaxillary gland in the gland 

 itself. 



Ninth Nerve. — ^A small branch of this nerve is secretory 

 and vaso-dilator to the parotid gland. Its cell-station is 

 the otic ganghon. 



Vagus. — The fibres are motor to the bronchial muscles, 

 the oesophagus, stomach and small intestine, secretory to 

 the glands of the stomach, and inhibitory to the heart. 

 The cell-stations are situated peripherally, e. g. in the heart, 

 at the sino-auricular node. In the intestine they are 

 probably represented by the cells of Auerbach's plexus. 



Sacral Autonomic 



The pre-ganglionic fibres form the pelvic nerve or nervus 

 erigens. The cell-stations are in the hypogastric plexus 

 situated at the neck of the bladder. Stimulation causes 

 vaso-dilatation of the penis (erection), contraction of the 



