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PLATE XXXIX. 



MUSCLES 



A Sterno-mastoid. 



A' Its separate sternal origin. 



B Sterno-hyoid. 



C Sterno-thyroid. 



D Thyro-hyoid. 



E Omo-hyoid. 



E' Tendon of omo-hyoid. 



F Hyoglossus. 



G Stylo-hyoid. 



H Digastric. 



I Thyro-hyoid membrane. 



K Supra-liyoid aponeurosis, tying the 



tendon of digastric to hyoid bone. 

 L Mylo-hyoid. 

 M Masseter. 

 N Platysma. 

 Parotid gland. 

 P Submaxillary gland. 

 R Retrahens aurem. 

 S Mastoid process. 

 T Pectoralis major. 

 V Clavicle. 



VESSELS 



a Facial artery. 



b Submental branch of facial. 



c Posterior auricular artery. 



d External jugular vein. 



f Anterior division of the temporo-maxil- 



lary vein joining facial. 

 / Facial vein. 

 g Anterior jugular vein. 

 h Submental vein which forms a junction 



with the anterior jugular. 



.NERVES 



1 Superficialis colli. 



2 Its communication with the facial. 



3 Great auricular. 



4 Infra-mandibular branch of facial. 



5 Mylo-hyoid branch of inferior dental. 



6 Posterior auricular branch of the facial. 



7 Hypoglossal. 



8 Thyro-hyoid branch of the hypoglossal. 



9 Branch from the descendens noni 



(cervicis) to the sterno-hyoid. 



In this plate great care was taken to keep the anterior edge of the sterno-mastoid 

 as nearly in its normal position as it was possible. 



To mark out the course of the external jugular vein draw aline from the angle of 

 the jaw to the middle of the clavicle ; the vein runs deep to and parallel with the fibres 

 of the platysma muscle, thus in venesection the incision must be made transversely to 

 the course of the vein, so that the muscle fibres may gape and expose it. 



The posterior external jugular, very variable in size, is the remains of an im- 

 portant foetal vein which drained the blood from the lateral sinus through the post-glenoid 

 foramen. This persists in the adult as the mastoid vein which communicates with the 

 lateral sinus and empties externally into the posterior external jugular. (Professor 

 Macalister considers this the true external jugular.) 



The anterior jugular is very variable in size, and its communication across the front 

 of the neck with the one on the opposite side must be borne in mind during tracheotomy, 

 as it is often much congested. In the lower part of its course under the sterno-mastoid 

 it runs parallel to the clavicle, and in tcnotomy of the muscle for torticollis this should be 

 remembered. 



