956 HUMAN ANATOMY. 



from a bursal tumor (thyro-hyoid) by the fact that the former is above, the latter 

 below, the hyoid bone. 



Enlargement of a submaxillary node, as of a parotid node, may, particularly 

 if it lies within the sheath of the gland, be mistaken for a growth of the gland itself. 

 The latter — as compared with the parotid — is, however, much less closely and hrmly 

 enveloped -by its capsule, is more superficial, and is not in near relation to such 

 important structures. On the other hand, the wide area which drains into the sub- 

 maxillary nodes — the middle of the forehead and of the face, the inner portions of 

 the lids, the mouth, pharynx, anterior portion of the tongue, gums and teeth of the 

 lower jaw — renders them especially liable to pyogenic or tuberculous or syphilitic 

 infection, or to secondary involvement in carcinoma of any of these regions — espe- 

 cially of the tongue or lower lip. In examining for enlargement of these nodes, the 

 chin, should be lowered so as to relax the depressors of the lower jaw and the deep 

 cervical fascia and permit of more accurate palpation of the region. When these 

 submaxillary nodes require removal for infectious or malignant disease, the salivary 

 gland is often involved and must be removed with them. On account of its accessi- 

 bility and the laxity of its capsular connections, enucleation of this gland is easily 

 accomplished. The relation of the facial artery lying close to the upper part of its 

 deep aspect — which it grooves — before crossing the jaw in front of the masseter 

 muscle should be remembered. 



The efferent vessels from all these nodes — suboccipital, mastoid, parotid, and 

 submaxillary — enter into the superficial cervical nodes, the efferent vessels from 

 which, in their turn, enter the deep cervical nodes (page 957). Extracranial lesions 

 of an irritative kind will thus first show themselves in enlargement of the first 

 mentioned groups ; if the irritation is continued, the superficial cervical nodes will 

 enlarge ; and if it persists and is sufficiently severe, the deep cervical will also 

 participate in the enlargement (Macewen). As the intracranial lyrpph-paths, having 

 their origin in the cerebral pia mater and the choroid plexuses of the ventricles, 

 pass out of the skull in company with the internal carotid and vertebral arteries and, 

 lower, the internal jugular vein and empty into the deep cervical nodes, these latter 

 are, theoretically, first affected by intracranial irritation. As they lie beneath the 

 cervical fascia, their enlargement may not be early noticed. These ^'ariations in the 

 seat of glandular swelling cannot, however, be relied upon as a basis for a positive 

 differential diagnosis between intracranial and more superficial (extracranial) sources 

 of irritation or infection. 



THE LYMPHATICS OF THE NECK. 

 The Lymph-Nodes. 



The principal group of nodes in the neck region is that which is situated along 

 the course of the internal jugular vein, forming the jugular plexus ( plexus jugularis). 

 It consists of a variable, but usually large, number of nodes and is interposed in the 

 pathway followed by the entire lymphatic system of the head and neck. It is prac- 

 tically a continuous chain of nodes, extending the entire length of the neck, but for 

 convenience in description it is convenient to regard the nodes as forming two sub- 

 groups which are named the superior and infe^'ior deep cervical 7iodes. In addition 

 to these some smaller groups occur more superficially, forming what are termed the 

 superficial cervical nodes, so that altogether there are three main groups of nodes in 

 the cervical region. 



The superficial cervical nodes (lymphoglandulae cei"vicales stiperficiales) 

 may conveniently be divided into two subgroups, both of which are composed 

 of rather small and somewhat inconstant nodes. The external Jiigular nodes, as 

 their name indicates, are situated along the course of the external jugular vein, 

 and consequently rest upon the outer surface of the sterno-cleido-mastoid muscle. 

 They occur a little below the lower extremity of the parotid gland (Fig. 796), 

 and are usually two or three in number, one or two additional nodes sometimes 

 being present at a somewhat lower level. They receive afferents from the pinna 

 of the ear and from the parotid region, and their efferents pass over the anterior 

 border of the sterno-cleido-mastoid to open into the superior deep cervical nodes. 



