498 



THE NERVOUS SYSTEM. 



FIG. 128. 



ated beneath the base of the skull, on the inner side of the inferior max- 

 illary division of the fifth pair. It receives filaments of communication 

 from the carotid plexus ; a motor root from the facial by the small super- 

 ficial petrosal nerve, as well as one or two short fibres from the infe- 

 rior maxillary division of the 

 fifth pair; and a sensitive root 

 from the glossopharyngeal by the 

 nerve of Jacobson. Its branches 

 are sent to the internal muscle 

 of the malleus in the middle ear 

 (tensor tympani), to the circum- 

 flexus palati, and to the mucous 

 membrane of the tympanum and 

 Eustachian tube. 



The continuation of the sym- 

 pathetic nerve in the neck con- 

 sists of two and sometimes three 

 ganglia, the superior, middle, and 

 inferior, communicating with 

 each other and the cervical spinal 

 nerves. Its filaments follow the 

 course of the carotid artery and 

 its branches, forming by their 

 inosculations the corresponding 

 arterial plexuses, and supplying 

 fibres of distribution to the thy- 

 roid gland, the larynx, trachea, 

 pharynx, and oesophagus. By 

 the superior, middle, and infe- 

 rior cardiac nerves it also sup- 

 plies fibres to the cardiac plexus, 

 and through it to the heart. 



In the chest, the communica- 

 tions of the sympathetic ganglia 

 with the spinal nerves are double ; 

 each ganglion receiving two fila- 

 ments from the intercostal nerve 

 next above it. The nerves orig- 

 inating from the ganglia are dis- 

 tributed to the plexuses on the 

 thoracic aorta, and to those of the lungs and oesophagus. 



In the abdomen, the sympathetic system consists mainly of an aggre- 

 gation of ganglionic enlargements situated on the cceliac artery, known 

 as the semilunar or cceliac ganglion. From this centre a multitude 

 of diverging and inosculating branches are sent out, which, from their 

 common origin and radiating course, are termed the "solar plexus." 

 Its secondary plexuses, accompanying the branches of the abdominal 



GANGLIA AND NERVES OF THE SYMPATHETIC 



SYSTEM. 



