PRACTICAL DIRECTIONS. 459 



2. The superior vena cava (p. 316). Find its branches. Trace 

 the azygos as far back as the diaphragm without dissecting it at all. 



Find the division of the innominate (p. 318) into subclavian and 

 external jugular. 

 Trace next 



3. The external jugular (p. 319). Remove the skin from the 

 side of the face and trace its branches (Fig. 131). The internal 

 jugular, vena facialis profunda, the submentahs, and the deep 

 terminal branches of the posterior facial cannot be followed at this 

 time; veins shown on Fig. 131 should all be found, however. 



4. Trace the thyrocervical axis and its branches (p. 293). Add 

 them to your diagram of the subclavian. 



5. Follow the common carotid artery (p. 283) and internal 

 jugular vein (p. 320). Find the division of the common carotid into 

 its terminal branches and then dissect its lateral branches and those 

 of the internal jugular (see Fig. 119). 



6. The external carotid (p. 285, and Fig. 119). Follow its 

 branches with the exception of the internal maxillary. 



7. The internal maxillary (p. 287). Find its inferior alveolar 

 branch first and follow it by cutting away with bone-forceps the ven- 

 tral border of the lower jaw. To follow its other branches and those 

 of the carotid plexus, remove the zygomatic arch, cut the temporal, 

 masseter, and pterygoid muscles, and cut the mandible behind the 

 incisor teeth and remove it. The branches which pass into the 

 skull are not to be followed at present. The posterior facial vein 

 (p. 323), the vena facialis profunda (p. 323), and the submental vein 

 (p. 323) may be followed at the same time. 



8. The internal carotid (p. 285). Follow it to the point where 

 it enters the cranium. 



9. Trace the other branches of the costocervical axis (p. 292). 

 To do this, cut the arteries and nerves of the axilla on the side on 

 which they have been dissected, allowing the arm to fall backward. 

 Then trace the branches of the costocervical axis with tracer, scalpel, 

 and bone-forceps, taking care not to injure the vertebral artery. 

 Add these branches to your diagram of the subclavian. 



10. The vertebral artery (p. 291). Trace it to the foramen 

 transversarium of the sixth cervical vertebra. Then with bone-forceps 

 follow it to the atlas and into the atlantal foramen. Add this to 

 your diagram of the subclavian. 



11. The basilar artery (p. 291) and the other arteries of the 

 brain (p. 289) are best studied on a preparation, similar to that 

 shown in Fig. 121. To obtain such a preparation it is only neces- 

 sary to remove the brain (for directions, see p. 462) of a specimen 

 in which the arteries have been injected. 



(12. Veins of the brain and dura mater (p. 324). These can be 

 worked out only with much difficulty, except on specimens injected 

 with gelatine. The skull must be chipped away and the veins 

 followed without destroying them.) 



