474 DIGESTION. 



motion of the jaws in chewing a tasteless substance does not 

 induce secretion. The gland receives two secreting nerves, 

 one of which is derived from the facial, and the other from the 

 sympathetic. The branch from the facial is the lesser superfi- 

 cial petrosal nerve, which leaves the facial in the petrous por- 

 tion of the temporal bone, passes to the otic ganglion, and 

 thence to join the auriculo-tcmporal branch of the fifth, in 

 which it proceeds to the gland. These facts have been experi- 

 mentally ascertained by observing, first, that irritation of the 

 roots of the facial within the cranium determines flow of saliva 

 from the parotid gland ; secondly, that excitation of the fifth 

 nerve within the cranium has no such effect ; and, thirdly, 

 that after section of the facial nerve at its exit from the stylo- 

 mastoid foramen, the application of stimuli to the mouth de- 

 termines secretion from the parotid as before. These facts, 

 taken in combination, show that the secreting fibres for the 

 parotid are given off by the facial in its passage through the 

 petrous part of the temporal bone. This conclusion receives 

 direct confirmation from an experiment of Bernard, who found 

 that destruction of the facial nerve in the temporal bone stops 

 the secretion of the parotid. 



Of the three nerves given off by the facial in its passage 

 through the temporal bone, viz., the chorda tympani, the greater 

 superficial petrosal and the lesser, the last-mentioned was 

 proved by Bernard by exclusion to contain the secreting fibres 

 for the parotid, for he showed that the chorda could be divided 

 in the tympanum without affecting the parotid secretion ; and 

 j-ards the greater superficial petrosal, it was known ana- 

 tomically that it did not go to the parotid, and also found ex- 

 perimentally that excision of Meckel's ganglion had no effect 

 on that gland. Bernard's conclusion has received direct con- 

 firmation from later experiments, which have shown, first, that 

 the secreting function of the parotid gland is much impaired 

 by the extirpation of the otic ganglion, and entirely annulled 

 by section of the auriculo-temporal nerve. After division of 

 this nerve. Schiff has shown that discharge of saliva cannot be 

 induced by the application of stimuli to the mouth, and that 

 electrical excitation of the peripheral end excites secretion just 

 in the same way as excitation of the chorda tympani. 1 



1 For :i description of the method of dividing the facial at its exit from 

 tin- st\ lomastoid foramen, see Eekhard's JScitr'.ige y.nr Anatomic und 

 Physiologic, JM. III. p. 49. Section of the facial within the temporal 

 lione is described iii Bernard, Lemons sur la Physiol. et la Pathol. du 

 S\st. N'crv., II. ])]). r>8 and 141. As regards section of the chorda in 

 the tympanum, excision of the sphenopalatine ganglion, and division 

 >f the Lesser suj.erticial petrosal nerve, nee, Schirt, Physiol. de la Diges- 

 tion, tom. 1. ].. 2'J!. Excision of the otic ganglion, do. p. 227. For 

 the method of exciting the aurieulo-tcmporal nerve, see Nawrocki Stud, 

 d. Physiol lust, zu Brcslau, lit. IV. p. loo. 



