821 



SUBCLAVIAN ARTERIES. 



Branches of the inferior thyroid artery. 

 a. Arteria cervicalis ascendens. This branch 

 (arising from the upper convexity of the thy- 

 roid, where that vessel changes its direction to 

 pass downwards and inwards beneath the 

 carotid sheath) passes upwards on the super- 

 ficial surface of the scalenus anticus, parallel 

 and internal to the phrenic nerve. The cer- 

 vicalis ascendens (frequently as large as the 

 thyroid itself) furnishes numerous muscular 

 branches to the levator anguli scapulae, longus 

 colli, rectus capitis anticus major, and to the 

 scaleni muscles, some of which anastomose 

 with branches of the occipital artery ; it like- 

 wise gives off spinal branches, which enter the 

 spinal canal along the cervical nerves, and 

 are distributed to the cord, anastomosing both 

 within and without the canal of the vertebra 

 with the vertebral artery. 



By some anatomists the cervicalis ascen- 

 dens is regarded as a branch of the thyroid 

 axis, from which it not unfrequently arises ; 

 in some rare instances it has originated di- 

 rectly from the subclavian artery. Sometimes 

 it is of very large size, and takes the place of 

 the occipital artery or of the cervicalis pro- 

 funda. 



b. The inferior thyroid artery furnishes se- 

 veral descending branches, which from their 

 destination may be termed cesophageal, tra- 

 cheal, and bronchial. 



c. Terminal or thyroid branches. The 

 inferior thyroid artery becomes extremely 

 tortuous as it approaches the thyroid gland ; 

 at last it divides into two or three large 

 branches, which enter the gland by its deep 

 surface, and which, in the substance and around 

 the margin of the gland, communicate freely 

 with the corresponding artery from the oppo- 

 site side, and with the superior thyroids of" 

 the external carotid. 



The reader is now referred to the article 

 SCAPULAR REGION, in which the remaining 

 branches of the thyroid axis, viz. the supra- 

 scapular and transverse cervical arteries, have 

 already been followed to their ultimate distri- 

 bution ; it will be only necessary in this place 

 to describe the cervical portions of these two 

 collateral branches. 



2. Supra-scapular artery (Artcria transvcr- 

 salis humeri). This artery is at first directed 

 downwards, but having reached the shelter of 

 the clavicle, it passes nearly horizontally out- 

 wards to the superior costa of the scapula. It 

 crosses over the phrenic nerve, the scalenus 

 anticus muscle, and the subclavian vein ; it 

 then runs outwards in contact with the vein, 

 and bound to it by cellular tissue ; it next 

 passes across the subclavian artery and bra- 

 chial plexus of nerves, and finally arrives at the 

 supra-spinal fossa, which it enters by passing 

 over the superior ligament of the scapula. 



The supra-scapular artery has, anterior to it, 

 the sterno-mastoid muscle, the clavicle, and the 

 omo-hyoid and trapczius muscles. It accu- 

 rately corresponds to the base of the supra- 

 clavicular space. 



3. Arteria Transversals Colli. This artery 

 is larger than the preceding ; from its origin 



it passes transversely outwards over the sca- 

 lenus anticus muscle and the phrenic nerve ; 

 at the outer edge of this muscle, it inclines 

 backwards and runs through the midst of the 

 branches of the brachial plexus. The artery 

 at this stage crosses the summit of the omo- 

 clavicular triangle, above the level of the 

 subclavian artery. In the space between the 

 sterno-mastoid and the trapezius, the trans- 

 verse cervical artery gives off a large branch, 

 the cervicalis superficialis, which is destined 

 for superficial structures, integuments, pla- 

 tysma, glands, and superficial layer of mus- 

 cles. 



The cervicalis superficiahs ascends in the 

 posterior superior triangle of the neck, through 

 a chain of conglobate glands, and through the 

 meshes of the cervical plexus of nerves, anas- 

 tomosing with branches of the occipital and 

 vertebral arteries, and passing finally under 

 cover of the trapezius, to which it distributes 

 numerous twigs, as also to the levator anguli 

 scapulae and splenius. 



After this the continued trunk of the trans- 

 verse cervical artery is usually called posterior 

 scapular artery, which has elsewhere been 

 described. 



The posterior scapular, and the cervicalis 

 supcrjicialis arteries, very frequently arise se- 

 parately, instead of springing by a common 

 trunk from the thyroid axis; in such cases the 

 posterior scapular is usually given off by the 

 suhclavian artery external to the scaleni. 



IV, Arteria Cervicalis profunda. ~| These ar- 



V. Superior Intercostal Artery. ] teries (as 

 has been already mentioned) generally arise 

 by a short trunk common to both, from the 

 subclavian in its second stage. An analogy 

 may thus be observed between this trunk and 

 the aortic intercostal arteries ; for, like them, 

 it divides into an anterior or intercostal branch 

 (the superior intercostal artery), and a poste- 

 rior or muscular branch (the cervicalis pro- 

 funda). The cervicalis profunda passes from 

 its origin backwards and upwards, between 

 the transverse process of the last cervical ver- 

 tebra and the first rib. When a supernumerary 

 cervical rib exists, the artery then passes be- 

 tween this latter and the first dorsal rib. It 

 thus gains the posterior aspect of the neck, 

 and ascends between the spinous and trans- 

 verse processes of the vertebrae, separated from 

 the laminae by the deep layer of muscles, and 

 covered by the great complexus muscle. 



In this course the cervicalis profunda anas- 

 tomoses with the large muscular branches 

 which descend from the occipital and verte- 

 bral arteries. 



The deep cervical artery sometimes passes 

 backwards at a higher or lower level than that 

 above specified ; these deviations must be rare, 

 since none of them existed in 40 subjects ex- 

 amined specially with reference to this subject 

 by Cruveilhier. In the extensive tables col- 

 lected by Professor Quain, and which have 

 already been frequently alluded to in this ar- 

 ticle, seventeen instances are given where 

 this artery passed between the first and second 

 rib; in a very few examples, it escaped from 



