SECTION VII. 



THE DIGESTIVE SYSTEM. 

 CHAPTER XXXI. 



THE INNERVATION OF THE SALIVARY GLANDS. 



The general nature of THE NERVE CONTROL OF SECRETORY 

 GLANDS is most readily studied on the submaxillary gland of the 

 dog or cat. The responses are not exactly alike in the two animals, 

 but the results typify glandular innervation in general. 



Demonstration 8. A dog is anaesthetized preferably by 

 . urethane (p. 72) and tracheal and carotid cannulae are inserted. 

 An incision is made along the inner border of the ramus of the lower 

 jaw extending from the mouth to the angle of the jaw. The digas- 

 tric muscle is exposed and is strongly retracted outwards so as to 

 expose the mylohyoid muscle, the fibres of which run transversely 

 to the wound. The hypoglossal nerve is seen extending backwards 

 behind the posterior edge of the mylohyoid. A probe or blunt 

 dissector is pushed under the latter muscle and its fibres cut in the 

 same line as the main wound. This exposes the ducts of the sub- 

 maxillary (and sublingual) glands with the lingual nerve crossing 

 them. A ligature ,is tied on this nerveySew-- the d-uc4s and the 



t.t. -^-t<>^^|^^v>A^p^ 



nerve cut peripheral to the hgafture^after which it is traced up under 

 the ramus of the jaw, the small branch which arises from it and 

 proceeds forwards being cut. Just above where this branch comes 

 off another branch passes backwards and downwards to join the 

 ducts a short distance from the 'place of crossing of the lingual. 

 This is the chorda tympani nerve. It can be prepared for artificial 

 stimulation by tying a second ligature round the lingual nerve 

 above where the chorda arises and cutting above the ligature. 

 By holding up the piece of lingual by the two ligatures the elec- 

 trodes can be readily applied to the chorda. ' ' / 



J ^^ **4UC4LCZ4L 9*4O'CU'v>u4 



Before attempting to insert a cannula in Wharton's duct the 

 chorda should be stimulated with a feeble tetanizing current after 



226 



