652 TEXT-BOOK OF PHYSIOLOGY 



ligament of the lens whereupon the latter becomes more convex on its ant( 

 rior surface, and hence adjusted for near vision. These and similar facts 

 are shown by stimulation and division of these nerves either pre- or post- 

 ganglionic with induced electric currents. 



The Functions of the Bulbar Autonomic Nerves. The efferent pre- 

 ganglionic nerve -fibers contained primarily in the nerve of Wrisberg or pars 

 intermedia, and secondarily in the facial nerve may be divided into two 

 groups, viz.: (a) those passing by way of the great petrosal nerve to the spheno- 

 palatine ganglion, and (b) those passing by way of the chorda-tympani nerve 

 to the submaxillary and sublingual ganglia. The functions of the great 

 petrosal fibers together with their post-ganglionic continuations (the spheno- 

 palatine ganglion and its branches) are (a) To inhibit the contraction of the 

 blood-vessels of the mucous membrane of the nose, soft palate, upper part of 

 the pharynx, the roof of the mouth and upper lip, and (b) to augment the 

 secretion of the mucous glands of the corresponding region. The functions 

 of the chorda-tympani fibers and their ganglionic continuations (the sub- 

 maxillary and sublingual ganglia and their branches) are (a) To inhibit the 

 tonus of the blood-vessels of the submaxillary and sublingual glands and 

 (b) to augment the activities of their epithelium and thus increase their 

 secretions. 



The function of the efferent pre-ganglionic fibers contained in the trunk 

 of the glosso-pharyngeal nerve together with -their post-ganglionic continua- 

 tions (the otic ganglion and its branches) are (a) To inhibit the contraction 

 of the blood-vessels of the parotid gland and (b) to augment the activities of 

 its epithelium and thus increase its secretion. 



The efferent pre-ganglionic nerve-fibers contained in the trunk of the 

 vagus nerve together with their post-ganglionic continuations are as follows: 

 (a) To inhibit the tonus and contractile power of the heart-muscle; (b) to 

 inhibit and sometimes augment the contraction of the esophagus and of the 

 sphincter car dice] (c) to inhibit the tonus of the cardiac end of the stomach for 

 the purpose of receiving incoming amounts of food; (d) to augment the tonus 

 and the contractile power of the gastric musculature and the pyloric sphinc- 

 ter; (e) to augment and sometimes inhibit the tonus of the bronchial muscula- 

 ture; (/) to inhibit the sphincter muscle of the common bile duct and to aug- 

 ment the tonus and contractile power of the visceral muscles in the walls of 

 the gall-bladder; (g) to augment the tonus and contractile power of the vis- 

 ceral muscles of the walls of the small intestine, and (h) to augment and some- 

 times to inhibit the activities of the epithelium of the gastric and pancreatic 

 glands and thus increase their secretions. These various phenomena result 

 when these various efferent nerves are divided and their peripheral extremi- 

 ties are appropriately stimulated. 



The Functions of the Thoracic and Lumbar Autonomic Nerves. 

 The efferent pre-ganglionic nerve-fibers that leave the spinal cord in the 

 ventral roots of the thoracic and upper lumbar nerves together with their 

 post-ganglionic continuations, have been shown by experiment to be vaso- 

 motor (constrictor), secreto-motor, viscero-motor and in some animals pilo- 

 motor in functions. The origin, course and distribution of these nerve -fibers 

 have been stated on pages 377 and 473. The specific functions of these 

 fibers will depend on the regions of the body to which they are distributed 

 (See page 648.) 



