THE SUPERFICIAL CERVICAL REGION 385 



areolar space exists between the investing layer and the sheath of the subclavian 

 vessels, and in it are found the lower part of the external jugular vein, the descend- 

 ing clavicular nerves, the suprascapular and transversalis colli vessels, and the 

 posterior belly of the Omohyoid muscle. This space extends downward behind 

 the clavicle, and is limited below by the fusion of the costocoracoid membrane 

 with the anterior wall of the axillary sheath. (4) The jpretracheal fascia, which 

 extends inward in front of the carotid vessels, and assists in forming the carotid 

 sheath. It is further continued behind the Depressor muscles of the hyoid bone, 

 and, after enveloping the thyroid body, is prolonged in front of the trachea to 

 meet the corresponding layer of the opposite side. Above, it is fixed to the hyoid 

 bone, while below it is carried downward in front of the trachea and large vessels 

 at the root of the neck, and ultimately blends with the fibrous pericardium. This 

 layer is fused on either side with the prevertebral layer, with which it completes 

 the compartment containing the larynx and trachea, the thyroid gland, the 

 pharynx and oesophagus. 



Applied Anatomy. The cervical fascia is of considerable importa 

 of view. As will be seen from the foregoing description, it may be <! 

 (1) A superficial layer; (2) a layer passing in front of the trach%, and 

 ficial layer a sheath for the Depressors of the hyoid bone; (3) a prey 

 front of the bodies of the cervical vertebra-, and forming with the second 

 are contained the trachea, oesophagus, etc. The superficial layer form 

 for the neck. It is attached behind to the ligamentum nuchae and the 

 vical vertebra; above, it is attached to the external occipital protuberani 

 line of the occiput, to the mastoid process, to the zygoma and the mawl 

 to the manubrium sterni, the clavicle, the acromion process, and the 

 front it blends with the fascia of the opposite side. This layer opposes i 

 or new growths toward the surface, and pus forming beneath it has a ten 

 If pus is in the posterior triangle, it might extend backward under tht 

 the Sternomastoid, or downward under the clavicle for some distant 

 junction of the cervical fascia to the costocoracoid membrane. If the ] 

 anterior triangle, it might find its way into the anterior mediastinum, 

 of the layer of fascia which passes down into the thorax to become <i 

 cardium; but owing to the lesser density and thickness of the fascmj 

 frequently finds its way through it and points above the sternum. 1 

 is connected above with the hyoid bone. It passes down beneath tie 

 of the thyroid body and trachea to become continuous with the fibroiMl 

 Laterally it invests the great vessels of the neck and is connected with tl 

 the Sternomastoid. Pus forming beneath this layer would in all prMj 

 the posterior mediastinum. The third layer (the prevertebral fasciaVfl 

 base of the skull. Pus forming beneath this layer, in cases, for instafig 

 of the cervical vertebra, might extend toward the posterior and laa-ri 

 point in this situation, or might perforate this layer of fascia and 1 

 point into the pharynx (retropharynaeal abscess). 



In cases of cut throat the cervical fascia is of considerable impopi 

 involves only the superficial layer the injury is usually trivial, the tjj 

 injury to the external jugular vein, and the only special complicatMl 

 But where the second of the two layers has been opened up, and whertf ft 

 have been injured, serious results may ensue. 



The Sternomastoid (m. sternocleidomastoideus] (Fig. 30 

 muscle, which passes obliquely across the side of the neck, boil 

 two layers of the deep cervical fascia. It is thick and 

 part, but is broader and thinner at each extremity. It arise*, 

 the sternum and clavicle. The sternal portion is a roundec 

 in front, fleshy behind, which arises from the upper and at 

 piece of the sternum, and is directed upward, outward, 

 clavicular portion arises from the inner third of the superio 

 surface of the clavicle, being compose' 

 directed almost vertically upward. The 



