THE XECK 



11 Go 



drawn from the cricoid cartila^^es to tlio centre of tlie clavicl*-. The lowest c(»rd 

 (eighth cervical) is just ahovf and Ix'liind th<' sul»clavian artt-rv. 



Collateral circulation after ligature of the common carotid (tig. 677). — 

 This takes place hy means (jf (1) tiie free connnunication wiiich exists ])etween tlici 

 opposite carotids, both witliout and within the cranivnn; and (2) hv cnlargenn-nt 

 of the branches of the subclavian artery on the same side as that on which the 

 carotid has been tied. Thus, outside the cranium, the su])erif>r an<l inferior 

 tliyroids are the chief vessels employed (fig. <>77). Witliin the cranium the 

 vertebral n-placcs the internal enrotid. 



Collateral circulation after ligature of the second and third parts of the 

 subclavian (tig. 677 j. — Here the following three sets of vessels are tho.se chiefly 

 employed: 



The suprascapular, the posterior) .,, (The acromio-th..racic. infra- aii.l 



- ^ ' ^ "- witli - subscapular, and dorsalis scap- 



/ uhe. 



scapular, 



The superior intercostal, the aortic ') 

 intercostals, and the internal - 

 mammarv, ) 



with 



f Tlie long thoracic and scapular 

 [ arteries. 



Numerous unnamed branches") 

 passing through the axilla from - 

 branches of the subclavian, ) 



with 



Branches of the axillarv. 



Deep cervical fascia. — The arrangement of this mu.st be remembered — {a) 

 above, and {U) l)elow. the hyoid bone. The latter is far the more important. 



(a) Arrangement above the hyoid bone. — Here two chief layers, .superficial 



Fig. r>78. — Di.\geam of the Layers of the Deep Cervical Fascia ik a.\ A.nteho- 

 posTERioR Section opposite to the Sternum. (Tillaux.) 



^The prevertebral layer can be seen passing down in front of" the longiis c-olli.) 



\ Superficial layer of superficial 

 faacia 



Sterno-clavicular layer 



Reduplication of this layer pass- 

 ing behind the sterno-thyrold. 

 Tracheal layer separated from 

 the trachea, and encloslDK the 

 left innominate vein, and be- 

 coming continuous with the 

 pericardium 



Space occupied by aterno-byoid 



lyft innominalf irin 

 — Innominata 



Pericardium 



and deep, can he made out: — (i) The superficial, traced ujiwards from the hyoid 

 bone, encloi^es the submaxillary gland, jiassing over the mylo-hyoid, and. a.^cending. 

 gives off the masseteric and parotid fa.><cia-, and is attached to the lower border of 

 the zygoma, fii) The deeper layer, which forms the stylo-mandibular ligament, 

 is important in its i^wer of checking over-action of the external jiterygoid. (/<) 

 Below the hyoid bone. — The imi»ortance of the fascia here is infinitely greater. 

 70 



