572 



NECK. 



space. This nerve, where crossed by the external 

 jugular vein, gives one or two minute twigs, 

 which follow its direction toward the angle of 

 the jaw. 



The supra-clavicular and super-acromial are 

 the two superficial branches in which the 

 plexus terminates: as they descend, they di- 

 vide into a lash of twigs, which diverge in the 

 posterior triangle of the neck, and at various 

 heights pierce its fascia, become subjacent to 

 the platysma, and contribute to supply it. Their 

 ultimate branching takes a very wide range : the 

 inner filaments obliquely cross the clavicular 

 origin of the sterno-mastoid ; the outer, the 

 anterior fibres of the trapezius; the middle 

 ones, the clavicle itself; and are dis- 

 tributed, in their respective regions, to the in- 

 teguments of the scapula, shoulder, chest, and 

 sternum. 



The branch from \heportio dura, which enters 

 the neck, is the lower division of its cervico- 

 facial part. From near the angle of the jaw, 

 where it traverses the fascia, it passes toward 

 the hyoid bone, and supplies the platysma 

 from its deeper side. Some of these twigs, 

 approaching the cutaneous surface of the 

 muscle in the anterior triangle of the neck, 

 communicate with filaments of the anterior cer- 

 vical nerve. 



1. Mesial region of the neck. This presents 

 different relations, as considered above or below 

 the level of the os hyoides. 



Above the os hyoides, and extending from 

 the body of that bone to the symphysis of the 

 lower jaw, is the narrow space which separates 

 the anterior bellies of the digastric muscles. It 

 is an elongated triangle, broadest below where 

 the tendons of the digastrics are kept apart by 

 the body of the hyoid bone having its apex 

 above, where these, having expanded into the 

 fleshy anterior bellies, are infixed side by side 

 at the median line of the jaw. The platysmata 

 in their cellular sheath cover this space, and 

 sometimes decussate across it with each other. 

 The cervical aponeurosis likewise extends over 

 it, adhering to its bony limits, and strength- 

 ened by the tendinous slip, which is derived 

 from the digastric. Deeper than the digastrics 

 are seen the fibres of the mylo-hyoid muscles, 

 meeting in the median raphe, which runs along 

 the space. The natural direction of this raphe 

 is almost antero-posterior, and that of the fibres 

 which meet in it almost horizontally transverse : 

 but when (as in any operation on this part of 

 the neck) the head is thrown back and the chin 

 elevated, the raphe presents a considerable 

 downward slope, and the fibres of the mylo- 

 liyoid have a corresponding obliquity. The 

 same observation applies to the deeper fibres 

 which course from the tubercles within the sym- 

 physis to the body of the hyoid bone those, 

 namely, of the genio-hyoid and genio-hyo-glos- 

 sal muscles. This little region can hardly be 

 said to have any special surgical relations ; it 

 contains neither vessels nor nerves of size ; its 

 injuries only assume importance when they 

 extend beyond it into the adjoining digastric 

 space; its diseases derive no peculiarities from 

 their situation, and for the most part belong to 



the integuments, which are vascular, highly 

 folliculated, and in the male densely bearded : 

 sycosis often extends to them, and they are a 

 frequent seat of sebaceous tumours. 



Below the os hyoides, the anatomy, which 

 involves the surgical relations of the larynx and 

 trachea, becomes of extreme importance. Be- 

 tween the two layers of the fascia superficialis 

 the platysma no longer intervenes ; they ac- 

 cordingly lie together and are blended. The 

 vaginal processes of cervical fascia, which have 

 isolated the sub-hyoid muscles, become united 

 into a strong and single raphe along the middle 

 line, from above to within a short distance of 

 the sternal notch ; but here the layers remain 

 distinct, a superficial one fixing itself to the 

 notch and to the interclavicular ligament, while 

 the deeper one descends with the muscles into 

 the mediastinum. The interval contains loose 

 cellular tissue, and sometimes (as Burns no- 

 ticed) an absorbent gland. Accordingly, in the 

 very median line, an operator may expose the 

 larynx, trachea, or thyroid body without divi- 

 ding or displacing any portion of muscle ; but 

 a lateral deviation from this imaginary line 

 would imply an exposure of the sub-hyoid 

 muscles on one side or on the other. Indeed, 

 the muscles so nearly approach to the line in 

 question, and constitute in their laminar ar- 

 rangement so useful a guide to the subjacent 

 parts, that the bare possibility of avoiding them 

 is wisely neglected, and the surgeon learns 

 from them his nearness to the organs which 

 they cover. 



In tracing, from the hyoid bone downward, 

 the irregular profile of the air-tube, the finger 

 may distinguish through the integument the 

 following changes of outline. 1. A horizontal 

 semicircular notch, limited below by the pro- 

 minent angle of the thyroid cartilage, and cor- 

 responding, in the interval of the muscles, to 

 the thyro-hyoid membrane; the lateral parts of 

 this give passage, as we shall presently see, to 

 the laryngeal artery and nerve, but its mesial 

 part, with which alone we are now occupied, 

 has only a small twig from the thyroid artery 

 ramifying over it: the membrane is thick, and 

 composed of strong vertical fibres in the median 

 line ; it becomes weaker and of laxer tissue in 

 proceeding backward. Its deep aspect contri- 

 butes to the skeleton of the pharynx, and cor- 

 responds to the epiglottis, from the attached 

 portion of which it is separated only by cel- 

 lular tissue and the epiglottidean gland ; while, 

 above, the mucous membrane, in being folded 

 forward to the epiglottis, intervenes between it 

 and the membrane. This notch is frequently 

 invaded by the knife of the suicide ; and there 

 is perhaps no part of the neck on which a gash 

 may be inflicted with less serious injury : the 

 large vessels are far removed, and the larynx 

 lies below the blade, which may, if near to the 

 hyoid bone, enter the pharynx above the epi- 

 glottidean fold of mucous membrane, leaving 

 the epiglottis unhurt, or, if more nearly ap- 

 proached to the thyroid border of the space, 

 may partly or entirely sever that cartilage from 

 its inferior attachments. No special surgical 

 operation belongs to the space ; if indeed we 



