552 



HUMAN ANATOMY. 



ttg p «■■. .. 



Fig. 546. 



Hvoid bone 



below ; or, in other words, these two muscular forces are acting on the interposed 

 pericardium in opposite directions,' and so render it tense and resisting. • And the 

 special object, no doubt, of this piece of anatomy is that during a full inspiration, 

 when the lungs are distended with air and the right side of the heart gorged with 

 blood from a suspension of respiration, the heart should not be encroached upon by 

 the surrounding lungs." 



The prevertebral layer (r. Fig. 546) lying between the oesophagus and spine 

 passes in the mid-line directly into the posterior mediastinum; laterally — beyond the 

 scalenus anticus — it aids in forming the sheath of the subclavian vessels and accom- 

 panies them into the axilla. 



Another way of elucidating the practical effect of the somewhat complex dis- 

 tribution of the cervical fascia is to regard the three chief layers — superficial, middle, 

 and deep — as dividing the neck into four anatomical spaces (Tillaux ). 



1. Subcutaneous (Space i. Fig. 545) : between the skin and the superficial 

 layer. The most important structure in this space is the external jugular vein, which 

 perforates the fascia just above the middle of the clavicle. 



2. Intra-aponeurotic (Space 2, Fig. 546) : between the superficial and mid- 



dle (sterno-clavicular) layers. This 

 space does not exist in fact at the 

 summit of the neck where the two 

 layers are one, but at the base its 

 / depth is equal to the thickness of 

 the sternum. It may be continuous 

 with the space left at the top of the 

 sternum between the two leaflets of 

 the superficial layer attached to the 

 anterior and posterior borders of the 

 sternum, — Griiber's ' ' suprasternal 

 intra-aponeurotic space," " Burns' s 

 space." It contains fat and lym- 

 phatic glands, the sternal head of 

 the sterno-mastoid, and the anterior 

 jugular veins. It is not infrequently 

 the seat of abscess.- 



3. Visceral (Space 3 = 3<z -|- T^b, 

 Fig. 545): between the pretracheal 

 and prevertebral layers. This in- 

 cludes all the principal structures of 

 the neck. As it communicates di- 

 rectly with the thorax and axilla, 

 suppuration may travel in those di- 

 • rections. It is divided into minor 

 spaces (3^ and 3^) by a layer of fascia coming from the under surface of the sterno- 

 mastoid muscle and by the bucco-pharyngeal fascia, a thin layer that comes off from 

 the prevertebral fascia where it leaves the carotid sheath, and which lines the 

 constrictors of the pharynx, leaving between it and the layer applied to the spinal 

 column a small but easily distended space — retropharyngeal — in which infection 

 from pharyngeal lesions occasionally occurs. 



4. Retrovisceral (Space 4, Fig. 546): the space between the prevertebral fascia 

 and spinal column, including the longus colli and rectus capitis anticus, the sympa- 

 thetic nerve, etc. 



It is obvious in a general way that all infections beneath the middle layer of 

 fascia are more, likely to be serious than those superficial to it. 



But to summarize in a little more detail the practical relations of the cervical 

 fascia, we may conclude that superficial to the outer layer (a. Fig. 545) there might 

 occur from traumatism a wound of the external jugular, or from infection a spread- 

 ing cellulitis. The space is the seat of superficial phlegmons, which tend to spread 

 under the skin only (Space i. Fig. 545), and, iij the absence of tension, are unat- 

 tended by throbbing pain or marked constitutional symptoms. 



Space 2 



Burns's Space 

 Space 4 



Left 



\ 



innominate vein /,/^ftV/ C ^ 

 Aortic arch ^' •"/' -^^ 



Diagram showing relations of cervical fascia in longitudinal 



section. 



