216 HUMAN PHYSIOLOGY. 



the facial and sensor filaments from the glossopharyngeal and fifth 

 nerves ; sends filaments to the mucous membrane of the tympanic 

 cavity and to the tensor tympani muscle. 



4. The submaxillary ganglion, situated in the submaxillary gland, 

 receives filaments from the chorda tympani, sensor filaments from 

 the lingual branch of the fifth nerve, and filaments from the sym- 

 pathetic. The chorda tympani nerve supplies vaso-dilator and 

 secretor fibers to the submaxillary and sublingual glands. The 

 fifth nerve endows the glands with sensibility, while the sympa- 

 thetic supplies vaso-constrictor fibers to the blood-vessels of the 

 glands. 



Cervical Ganglia. 



The superior cervical ganglion is fusiform in shape, of a grayish- 

 red color, and situated opposite the second and third cervical ver- 

 tebra ; it sends branches to form the carotid and cavernous plexuses, 

 which branches follow the course of the carotid arteries to their 

 distribution; also sends branches to join the glossopharyngeal and 

 pneumogastric, to form the pharyngeal plexus. 



The middle cervical ganglion, the smallest of the three, is oc- 

 casionally absent ; it is situated opposite the fifth cervical vertebra ; 

 sends branches to the superior and inferior cervical ganglia and to the 

 thyroid artery. 



The inferior cervical ganglion, irregular in form, is situated oppo- 

 site the last cervical vertebra ; it is frequently united with the first 

 thoracic ganglion. 



The superior, middle, and inferior cardiac nerves, arising from 

 these cervical ganglia, pass downward and forward to form the deep 

 and superficial cardiac plexuses located at the bifurcation of the 

 trachea, from which branches are distributed to the heart, coronary 

 arteries, etc. 



The thoracic ganglia are usually twelve in number, and are 

 placed against the heads of the ribs behind the pleura ; they are 

 small in size and gray in color ; they communicate with the cerebro- 

 spinal nerves by two filaments, one of which is white, the other gray. 



The great splanchnic nerve is formed by the union of branches 

 from the sixth, seventh, eighth, and ninth ganglia ; it passes through 

 the diaphragm to the semilunar ganglion. 



The lesser splanchnic nerve is formed by the union of filaments 



