CIRCULATORY APPARATUS. 89 



Branches. 



An anastomosing branch, with the internal collateral form- 

 ing the supra-carpal arch above the pisiform bone. 



A few to the tendons and skin. 



One passing upwards, anastomosing with the interossei. The 

 digital vessels are similar to those of the posterior limb, with which 

 they will be described. 



COMMON CAROTIDS. 



These two vessels supplying the head and neck, arise by a com- 

 mon trunk, from the right axillary at its origin, called the cephalic. 

 This passes forward under the trachea to anterior entrance of the 

 chest, where it divides into its two branches; each common carotid 

 passes upward along the trachea to the larynx, where it divides 

 into the occipital, external and internal carotids. 



Branches. 



Small ones to the muscles, oesophagus and trachea. 



Thyro-laryngeal, to thyroid gland, larynx and pharynx. 



Accessory thyroid, to thyroid and cervical muscles. 



Occipital. 



Passes alongside of internal carotid, under inferior arch of 

 atlas, through anterior foramen in its transverse process, dividing 

 into occipito-muscular and cerebro-spinal. 

 Branches. 



Prevertebral, to muscles of neck and dura mater. 



Mastoid, through parieto-temporal canal to dura and temporal 

 muscles. 



Atloido-muscular, passes backward to anastomose with vertebral. 



Occipito-muscular, inward to rrruscles and skin of occipital 

 region. 



Cerebro-spinal. 



Enters spinal canal and divides into two branches, one of which 

 passes backward and unites with its fellow of the opposite side, 

 forming the median spinal artery.^ The anterior branch unites 

 with its fellow, forming the basilar. 



Basilar. 



Passes under the medulla, runs forward to the anterior border 

 of the pons. 

 Branches. 



Small vessels to pons, medulla and cranial nerves. 



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