64 



ELEMENTARY PHYSIOLOGY. XI. 



away the skin over the lower jaw. Cut through the 

 superficial muscles connecting the shoulder and sternum 

 with the head. 



Near the mid line of the lower jaw will be seen two 

 nerves on each side, the hypoglossal and the glosso- 

 pharyngeal. Near the symphysis of the jaw the hypo- 

 glossal which is the more superficial of the two lies 

 on the outer side of the glossopharyngeal (cp. Fig. 20). 



Fig. 20. p.h., petrohyoid muscle; gl. 9 glossopharyngeal nerve; %., hypo- 

 glossal nerve; ?;., vagus; /., laryngeal branch; j., internal jugular 

 vein; br., brachial nerve. 



Trace them backwards ; the hypoglossal crosses first the 

 glossopharyngeal and then the branches of the aorta. 

 The glossopharyngeal on coming to the aortic branches 

 runs towards the angle of the jaw, along the upper 

 border of a small band of muscle (part of the petro- 

 hyoid). 



|v The course of the vagus is most easily followed by 

 cutting away the sternum, putting a seeker through the 

 anterior part of the skull from behind and tying the 



