132 THE HEAD AND NECK 



omo-hyoid is freed and retracted upwards, and the veins., re- 

 ferred to above, are ligatured. In this process the transverse 

 scapular (supra-scapular) artery (p. 126) is exposed and pulled 

 aside. The brachial plexus lies above and to the lateral side of 

 the subclavian artery, and especial care must be taken to avoid 

 injuring the lower trunk, which frequently lies behind the vessel. 

 By retracting the sterno-mastoid medially, the lateral border 

 of the scalenus anterior, which forms an important landmark, 

 is brought into view. If the finger is carried downwards along 

 this border till the tip rests on the scalene tubercle, the pulp of 

 the finger can feel the pulsations of the artery. As the ligature 

 is applied close to the lateral border of the scalenus anterior, 

 great care must be taken lest the pleura, which lies behind the 

 second part of the artery, be damaged. 



In Interscapulo-Thoracic Amputation the clavicle is divided, 

 or its middle third is resected and the subclavius muscle is 

 removed. This enables the surgeon to ligate the subclavian 

 artery and vein and to cocainise the trunks of the brachial plexus. 



The Deep Cervical Lymph Glands lie mainly under cover 

 of the sterno-mastoid, but they project partly into the anterior 

 and partly into the posterior triangle. They can be subdivided 

 into four groups, upper and lower posterior and upper and lower 

 anterior (Stiles). 



1. The Upper Posterior Group lies on the roots of the 

 cervical plexus and extends into the posterior triangle. They 

 receive afferents from the pharynx, the occipital, and the mastoid 

 lymph glands, and from the upper anterior group. When these 

 glands are enlarged, the accessory nerve may be found embedded 

 in their midst, or lying immediately under the investing layer 

 of the deep cervical fascia, on the surface of the glandular mass. 



2. The Lower Posterior Group lies in relation to the posterior 

 belly of the omo-hyoid and superficial to the prevertebral fascia. 

 They may be involved alone in ascending infection from the 

 axillary glands, as in malignant disease, or they may be attacked 

 by a descending infection from the upper groups, or by a lateral 

 spread from the lower anterior group. 



3. The Upper Anterior Group is situated around the upper 

 part of the carotid sheath, but a few of the glands lie within the 

 sheath in close contact with the internal jugular vein. They 

 receive afferents from the interior of the cranium, the pharynx, 

 mouth, nose, upper part of larynx, etc., either directly, or in- 

 directly from the submental and submaxillary lymph glands. 



