608 THE VASCULAR SYSTEMS 



submaxillary gland, superficial to which is the facial vein, while embedded in it are 

 the facial artery, and its glandular branches; beneath this gland, on the surface of 

 the Mylohyoid muscle, are the submental artery and the mylohyoid artery and 

 nerve. The posterior part of this triangle is separated! from the anterior part, 

 by the stylomaxillary ligament: it contains the external carotid artery, ascending 

 deeply in the substance of the parotid gland; this vessel here lies in front of, and 

 superficial to, the internal carotid, being crossed by the facial nerve, and gives off in 

 its course the posterior auricular, temporal, and internal maxillary branches; more 

 deeply are the internal carotid artery, the internal jugular vein, and the vagus 

 nerve, separated from the external carotid by the Styloglossus and Stvlopharyn- 

 geus muscles and the glossopharyngeal nerve. 1 



The suprahyoid triangle is limited behind by the anterior belly of the Digastric, 

 in front by the middle line of the neck between the symphysis menti and the hyoid 

 bone, below by the body of the hyoid bone; its floor is formed by the Mylohyoid. 

 It contains one or two lymph nodes and some small veins; the latter unite to 

 form the anterior jugular vein. 



The posterior triangle is bounded, in front, by the Sternomastoid muscle; 

 behind, by the anterior margin of the Trapezius; its base corresponds to the middle 

 third of the clavicle; its apex, to the occiput. The space is crossed, about an incii 

 above {he clavicle, bv the posterior belly of the Omohyoid, which divides it un- 

 equally into two, an upper or occipital and a lower or subclavian triangle. 



The occipital triangle, the larger division of the posterior triangle, is bounded, 

 in front, by the Sternomastoid; behind, by the Trapezius; below, by the Omo- 

 hyoid. Its floor is formed from above downward by the Splenius. Levator anguli 

 scapulae, and the Middle and Posterior scaleni muscles. It is covered by the 

 integument, the Platysma below, the superficial and deep fasciae; thp spinq.1 

 apppss'nry nerve is directed obliquely across the space from the Sternorrmstnid. 

 which it pierces, to the under surface of the Trapezius; below, the descending, 

 branches of the cervical plexus and the transversalis colli artery and vein cross 

 the space. A chain of lymph nodes is also found running along the posterior. 

 border of the Sternomastoid, from the mastoid process to the root of the neck. 



The subclavian triangle, the smaller of the two posterior triangles, is bounded, 

 above, by the posterior belly of the Omohyoid; below, by the clavicle, its base, 

 directed forward, being formed by the Sternomastoid. The size of the subclavian 

 triangle varies according to the extent of attachment of the clavicular portion of the 

 Sternomastoid and Trapezius muscles, and also according to the height at which 

 the Omohyoid crosses the neck above the clavicle. Its height also varies much 

 according to the position of the arm, being much diminished by raising the limb, 

 on account of the ascent of the clavicle, and increased by drawing the arm down- 

 ward, when that bone is depressed. This space is covered by the integument, 

 the Platysma, the superficial and deep fasciae, an.d crossed by the descending, 

 branches of the cervical plexus. Just above the level of the clavicle the third 

 portion of the subclavian artery curves outward and downward from the outer 

 margin of the Scalenus anticus, across the first rib, to the axilla. Sometimes this 

 vessel rises as high as an inch and a half above the clavicle, or to any point inter- 

 mediate between this and its usual level. Occasionally it passes in front of the 

 Scalenus anticus or pierces the fibres of that muscle. The subclavian vein lies 

 behind the clavicle, and is usually not seen in this space; but it occasionally rises 

 as high up as the artery, and has even been seen to pass with that vessel behind 

 the Scalenus anticus. The brachial plexus of nerves lies above the artery, and 

 in close contact with it. Passing transversely behind the clavicle are the supra- 



1 The remark made about the carotid triangle applies also to this one. The structures enumerated as con- 

 tained in its posterior part lie, strictly speaking, beneath the muscles which form the posterior boundary of 

 the triangle; but as it is very important to bear in mind their close relation to the parotid gland, all these parts 

 are spoken of together. 



