THE HEAD AND NECK. 



69 



tween the subclavian vein and artery on the outer surface of the first rib. You 

 will again see the nerves that are to form the brachial plexus coming through 

 between the scalenus anticus and scalenus medius muscles above the subclavian 

 artery. You will find the phrenic nerve lying on the anterior surface of the 

 scalenus anticus muscle. You will in time trace it between the subclavian vein 

 and artery into the thorax, down in front of the root of the lung, to the diaphragm, 

 and all the serous membranes continging the diaphragm, for distribution. 



Origin of the Scaleni Muscles. To aid the memory, remember the num- 

 erals 3, 6, 3. The scalenus anticus arises from the anterior tubercles of the lower 

 three transverse processes ; the scalenus medius from the lower six ; the scale- 

 nus posticus from the lower three. The last two arise from posterior tubercles. 

 Remember, scarcely any two dissections will show exactly the same origin ; 



I!i</ht posterior cerebral artery 



Left posterior cerebral artery 



Basilar artery 



BASILAR PROCESS, OCCIPITAL BONE 



Intracranial portion of vertebral artery 

 Reetus capitis lateralis muscle 



FIRST CER VIC A L NER VE 



Commencement of vertebral vein 



SECOND CERVICAL NERVE 



Vertebral plexus of reins 



THIRD CERVICAL NERVE 



Vertebral portion of vertebral artery 

 FOURTH CERVICAL NERVE 



Vertebral plexus of veins 

 FIFTH CERVICAL NERVE 



SIXTH CERVICAL NERVE 



Inferior thyroid artery 



Longus colli muBde 



Cervical portion of vertebral artery 



Internal jugular vein, hooked a little 

 aside 



Vertebral vein, cut 

 Subclavian artery 



Right and left svpe- 



* rior cerebellur 



arteries 



OCCIPITAL BONE 



Bectus capUis pos- 

 ticus minor mus- 

 cle 



Occipital portion of vertebral artery 



Arleria princejm cerrlcis 



Semispiualis colli muscle 



Deep cervical artery 



Scalenus anticus muscle, cut 

 Thyroid axis, hooked a little aside 

 Subclarian vein 



FIG. 40. SCI! KM K OK THK YKRTKUKA1, ARTKRY. 



The internal jugular and vertebral veins are hooked aside to expose the artery. 



hence it is, scarcely any two authors will give the origin of these muscles alike. 

 The foregoing is a general average and easily remembered 3, 6, 3. 



The Levator Anguli Scapulae Muscle. It is necessary to have exact 

 knowledge of this muscle, to understand your dissection of the plexuses. This 

 muscle arises from the posterior tubercles of the transverse processes of the 

 upper three. You will find the tendons of origin of this muscle becoming fleshy. 

 They will unite to form a flat muscle, two inches broad. This muscle will be 

 inserted into the middle lip of the vertebral border of the scapula, from the 

 superior angle to the vertebral end of the scapular spine. Find its nerve-supply 

 coming from the cervical plexus. 



