THE FACIAL AND OCCIPITAL ARTERIES. 399 



Xizc. This artery varies much in size, and in the extent of its distribution. It has been 

 observed, very rarely however, to end as the submental, not reaching the side of the face : 

 in some cases it supplies the face only as high as the lower lip ; and it often fails to supply 

 the lateral nasal and angular branches. The deficiency of the facial artery is most frequently 

 compensated for by an enlargement of the nasal branch of the ophthalmic at the inner side of 

 the orbit ; occasionally by branches from the transverse facial, or internal maxillary artery. 

 As a rare occurrence it has been found larger than usual, and replacing the nasal and 

 frontal branches of the ophthalmic. 



Jii-anehes. The ascending palatine artery is in some instances transferred to the external 

 carotid. This branch varies in size and the extent to which it reaches. Not unfrequently it 

 is expended without furnishing any branch to the soft palate. When it is thus reduced in 

 size, the pharyngeal artery takes its place in the soft palate. The sitlmoital branch has been 

 observed to take its rise from the sublingual artery. On the other hand, the facial artery, 

 instead of the lingual, sometimes furnishes the branch which supplies the sublingual gland. 

 The two coronary arteries sometimes arise by a common trunk ; and one or other of these 

 vessels may be smaller than usual, the corresponding artery of the opposite side being 

 enlarged and supplying the deficiency. 



4. Occipital artery (iv). The occipital artery, arising from the posterior 

 part of the external carotid, usually opposite the facial or a little higher up, is 

 directed upwards and backwards, beneath the posterior belly of the digastric 

 muscle, to the interval between the transverse process of the atlas and the mastoid 

 process of the temporal bone. Here it turns backwards along the skull, lying in 

 the occipital groove of the temporal bone, internal to the mastoid process and the 

 sterno-magtoid, splenius, trachelo-mastoid and digastric muscles, and resting on the 

 rectus lateralis, obliquus superior, and complexus. Lastly, issuing between the 

 cranial attachments of the sterno-mastoid and trapezius, it ascends beneath the 

 integument on the back of the head, accompanied by the great occipital nerve, and 

 divides into branches, which are distributed upon the upper and back part of the 

 cranium. While in the neck, the occipital artery crosses over the internal carotid 

 artery, the pneumo-gastric and spinal accessory nerves, and the internal jugular 

 vein ; and the hypoglossal nerve winds from behind forwards over it at its origin. 



Branches. (a) Small muscular offsets to the digastric, stylo-hyoid, splenius, and 

 trachelo-mastoid muscles, and one of larger size to the sterno-mastoid. This sterno- 

 mastoid branch is very constant : arising generally from the occipital artery close to 

 its commencement, but not unfrequently from the trunk of the external carotid, it 

 turns downwards over the loop formed by the hypoglossal nerve, and enters the 

 muscle in company with the spinal accessory nerve. 



(&) A small twig, the mastoid branch, enters the skull through the mastoid 

 foramen, and ramifies in the diploe and the dura mater. 



(c) The cervical branch, ramus cervicalis princeps, is distributed to the muscles 

 of the upper and back part of the neck. Descending a short way, this vessel divides 

 into a superficial and a deep branch. The former ramifies beneath the splenius, 

 sending offsets through that muscle to the trapezius ; while the deep branch passes 

 beneath the complexus, and anastomoses with branches of the vertebral artery, and 

 with the deep cervical artery. The size of this branch varies much, and it is often 

 represented by two or more smaller offsets. 



(d) The superficial or cranial branches pursue a tortuous course between the 

 integument and the occipito-frontalis muscle ; and in proceeding upwards on the 

 skull they separate into diverging branches, which anastomose freely with one 

 another, as well as with the branches of the opposite artery, of the posterior auricular 

 artery, and of the superficial temporal artery. 



Varieties. Origin. The occipital artery is occasionally derived from the internal 

 carotid, or from the ascending cervical branch of the inferior thyroid an offset of the 

 subclavian artery. 



Course. The occipitial artery sometimes passes outside the trachelo-mastoid instead of 

 internal to it. The chief portion of the vessel has been found to pass over the sterno-mastoid 



