714 THE LYMPHATIC SYSTEM 



the same is true of the submucous vessels of the lower lip. The subcutaneous vessels, on the 

 other hand, passing to the submental nodes, anastomose freely, an important fact in connection 

 with the extension of cancer of the lower Up. 



The lymphatics of the auricle and external auditory meatus. — The lymphatic 

 plexus in the auricle, external auditory meatus, and the outer side of the tympanic 

 membrane is an abundant one. An anastomosis has been described between a 

 scanty plexus on the inner side of the tympanic membrane and the plexus on the 

 outside. The collecting vessels pass to three sets of nodes: — (1) those from the 

 external and internal surface of the auricle and the posterior part of the external 

 auditorj^ meatus pass to the posterior auricular nodes; (2) those from the lobule, 

 the helix, a part of the concha and the outer portion of the external auditory mea- 

 tus pass to the inferior auricular and superficial cervical chain; some of the vessels 

 from the first and second areas also run to the deep cervical group; (3) an anterior 

 group from the tragus and part of the external auditory meatus consisting of from 

 four to six trunks, pass to the anterior auricular nodes, which are connected with 

 the parotid nodes. 



3. THE DEEP LYMPHATIC NODES OF THE HEAD AND NECK 



The deep cervical chain is the largest mass of nodes in the neck. It consists 

 of from fifteen to thirty nodes, which lie along the entire course of the carotid 

 artery and internal jugular vein. This chain receives vessels from all the super- 

 ficial nodes, also directly from the skin, as well as from the entire mucous mem- 

 brane of the respiratory and alimentary tracts in the head and neck. Thus it 

 drains both the superficial and the deep structures. 



For convenience of description this long chain, though usually continuous, is 

 divided into two groups — (1) a superior group, lying above the level at which the 

 omo-hyoid muscle crosses the carotid artery, and (2) an inferior or supra-clavicular 

 group, lying below that level. 



(1) The superior deep cervical nodes [Igl. cervicales profundae superiores]. — • 

 This group of nodes extends from the tip of the mastoid process to the level at 

 which the omo-hyoid muscle crosses the common carotid artery. The dorsal and 

 smaller nodes of the chain lie on the splenius, levator scapulae, and scalene mus- 

 cles. They drain the skin of the back part of the head, both indirectly and 

 directly, and receive (1) efferents from the occipital and posterior auricular nodes, 

 (2) a large vessel from the skin of the occipital part of the scalp, (3) some trunks 

 from the auricle, and (4) cutaneous and muscular vessels from the neck. 



The ventral nodes of the chain lie on the internal jugular vein. They drain 

 the face both directly and indirectly, as well as the deeper structures of the head 

 and neck. They show especially well in fig. 563 in connection with the tongue. 



(2) The inferior deep cervical [Igl. cervicales profundae inferiores] or supra- 

 clavicular nodes lie in the supra-clavicular triangle. In the upper part of the tri- 

 angle the nodes rest on the splenius, the levator scapulae, and the scalene muscles, 

 while at the base of the triangle they are related to the subclavian artery and the 

 nerves of the brachial plexus. They drain a wide area, receiving vessels from the 

 head, neck, arm, and thoracic wall. They are connected with the superior deep 

 cervical chain, and receive afferents from the axillary nodes, and, in addition, they 

 receive vessels directly from the back of the scalp, from the skin of the arm, and 

 from the pectoral region. Thus it will be seen that a large part of the lymph 

 of the head and neck, as well as some from the arm and thorax, passes through 

 these nodes. Their efferents unite to form the jugular trunk, which ends at the 

 junction of the internal jugular and subclavian veins. 



In the descriptions of the deep lymphatic vessels certain additional groups of 

 nodes will be considered, which may be regarded as outlying groups from the deep 

 cervical chain. 



4. THE D1^:I-:P lymphatic vessels of THE HEAD AND NECK 



The lymphatics of the brain. — It is now recognised that there are no lymph- 

 atics in llic hiaiii and (iord, so tliat the function of absorption must be accom- 

 plished by means of the veins. Tliere is an abundant exudation of lymph around 

 the nervous system into the subdural space, which is connected with the central 



