DISSECTION OP THE HEAD AND NECK. 145 



and then lies in a groove on the surface of the gland ; but this part of 



its course is not to be examined at present. At the lower extremity of 



the parotid it is joined by a large branch — the submaxillary vein ; and 



it then passes into the jugular furrow, in which it descends to the 



entrance to the chest. The upper boundary of the furrow, it will now 



be observed, is formed by the mastoido-humeralis, and the lower by the 



sterno-maxillaris. In the upper half of this groove the vein rests on the 



subscapulo-hyoideus muscle, which there separates the vessel from the 



carotid artery ; but in the lower half the vein rests on the side of the 



trachea, and is in direct contact with the carotid, which lies above and 



slightly internal to it. The jugular of the left side differs from the 



right in being related, in the lower part of the groove, to the oesophagus 



as well as the trachea. At the entrance to the chest the right and left 



jugulars unite with one another and with the axillary veins, thus forming 



the initial portion of the anterior vena cava. 



The jugular receives, in the part of its course now exposed, the 

 following branches : — 



1. The Submaxillary or Facial vein, which joins the jugular at an 

 acute angle in which lies the inferior extremity of the parotid gland. 



2. The Thyroid vein, bringing blood from the thyroid body and 

 larynx. 



3. Innominate cutaneous, muscular, cesopliageal, and tracheal branches, 

 whose disposition is not constant. 



4. The Cephalic vein, which enters the jugular near its termination. 

 [The single jugular of the horse is generally said to be the representative of the external 



jugular of man ; the internal jugular, under that view, being undeveloped in the soliped. 

 This I believe to be a mistake, and for the foUowing reasons. The external jugular of 

 man runs on the surface of the platysma (panniculus), and never beneath it as does the 

 vein of the horse ; moreover, it is a vessel of very variable volume, being frequently small, 

 and sometimes absent. On the other hand, the cervical part of the internal jugular of 

 man has a situation exactly corresponding to that of the horse's vein, save that the latter 

 vessel is generaUy superficially placed to the subscapulo-hyoid (omo-hyoid) ; and m the 

 horse I have seen the jugular, otherwise normal, pass under that muscle, keeping com- 

 pany with the carotid artery for the whole of its course.] 



The Stbeno-maxillaeis (Plate 27). This muscle corresponds to the 

 inner portion of the stemo-mastoid of man. It arises from the carini- 

 form cartilage of the sternum, and is inserted by a flat tendon into the 

 angle of the inferior maxilla. In the lower half of the neck the muscle 

 lies below the trachea, and covers the sterno-thyro-hyoideus muscle. 

 In this position the right and left muscles are in contact, but about the 

 middle of the neck they diverge, and cross obliquely upwards and 

 forwards over the trachea and the subscapulo-hyoideus muscle. Its 

 terminal tendon is included between the parotid and submaxillary glands. 

 The upper edge of the muscle forms the lower boundary of the jugular 

 furrow In its lower part the muscle is thick and rounded, but it 

 becomes more slender and flattened as it is traced upwards. 



