DISSECTION OF THE VASCULAR SYSTEM. 59 
12. The Internal Maxillary Artery. Just beyond the 
origin of the facial the external carotid divides into 
‘two branches, the larger being the internal maxillary, 
distributed to the inner side of the mandible, maxilla, 
etc.; the smaller branch is 
13. The Temporal Artery, distributed to the mus- 
cles and integument of the side of the head. 
14. The Right Sub-clavian Artery. Beyond the ori- 
gin of the two common carotids the brachio-cephalic 
artery is known as the right sub-clavian artery. The 
chief branches are as follows: 
I5. The Vertebral Artery, a branch which passes 
dorsally to reach the vertebral canal of the spinal 
column, through which it reaches the interior of the 
skull to supply the brain. 
16. The Superior Intercostal Artery comes off quite 
close to the vertebral, sometimes forming a branch of 
Pit le is distributed to the three: antenor ribs. 
17. The Sternal (7x¢ernal mammary) Artery, given 
off a little beyond the last. In company with the 
artery of the other side it passes along the under sur- 
face of the sternum, supplying it and the adjacent por- 
tions of the ribs. 
18% The Thyroid Axis arises usually somewhat 
nearer the heart than the last, but from the anterior 
border of the sub-clavian. It seems to be homologous 
with the thyroid axis of human anatomy, but has a 
different distribution. It divides into branches which 
supply the muscles of the root of the neck and of 
the supra-scapular region. 
I9. The Pectoral Branches. Beyond the thyroid 
axis the sub-clavian artery, now knownas the axzllary, 
gives off one or two branches which are distributed 
chiefly to the pectoral muscle. 
