DISSECTION OF THE HEAD AND NKCK 269 



venae jugularis superior) situated? What is the relation of this 

 vein to the other structures contained within the " vascular 

 sheath" of the deep cervical fascia! Observe the entrance of 

 the inferior petrosal sinus (sinus petrosus inferior) into the 

 superior bulb of the vein. Pass a probe through the sinus from 

 the skull cavity into the bulb. Find the pharyngeal plexus 

 (plexus pharyngeus) and tributary veins (Vv. pharyngeae). 

 The following tributaries of the internal jugular have been 

 studied already, but they may now be reviewed with advantage : 



(a) Lingual vein (V. lingualis). 



(b) Superior thyreoid veins (Vv. thyreoideae superior -es). 



(c) Common facial vein (V. facialis communis). 



Slit open the internal jugular vein and observe the valve. 

 In what part of the vein is it situated? How many flaps are to 

 be seen! 



Hypoglossal Nerve (N. hypoglossus). (Vide Figs. 92 and 112.) 



Divide the V. jugularis interna five centimetres below the 

 base of the skull and turn the upper part upward so as to expose 

 the N. hypoglossus better as it emerges from the canalis hypo- 

 glossi (0. T. anterior condyloid foramen). Note the close con- 

 nection of the nerve with the ganglion nodosum of the N. vagus. 

 At what point does the N. hypoglossus enter the anterior triangle 

 of the neck! Note its relation to the A. occipitalis. Demon- 

 strate, if possible, the branches of communication (1) with the 

 superior cervical ganglion of the sympathetic, (2) with the gan- 

 glion nodosum of the N. vagus, and (3) especially with the Nn. 

 cervicales I. and II. What is the significance of the fibres to the 

 N. hypoglossus from the cervical nerves! Make a list of (1) the 

 muscles supplied by the N. hypoglossus proper and (2) the mus- 

 cles supplied by fibres of cervical nerves running in the N. 

 hypoglossus. Eeview the branches of the N. hypoglossus already 

 studied, viz., (1) ramus descendens, (2) ansa hypoglossi, (3) 

 ramus thyreohyoideus, and (4) rami linguales. 



Accessory Nerve (N. accessorius) (O. T. Spinal Accessory). (Vide 



Fig. 92.) 



What is its relation to the N. vagus and N. glossopharyngeus 

 in the jugular foramen! Study 



(a) Internal ramus (ramus internus] (0. T. accessory portion). Follow 

 it to where it fuses with the N. vagus. 



