PRACTICAL CONSIDERATIONS: THE NECK. 553 



The space between cand b (3/^, Fig. 545) is occupied only by the great vessels 

 and the pneumogastric. Infection there — i.e., within the sheath — may mean de- 

 scending thrombosis from original infection of a cerebral sinus, or may have spread 

 directly through the sheath from infected tracts of cellular tissue outside. Behind 

 b. Fig. 545 (retrovisceral space), suppuration is not uncommon as a result of verte- 

 bral disease. Direct infection through the pharyngeal wall usually involves the 

 retropharyngeal space. In either case dysphagia and dyspnoea are usual for obvious 

 reasons. 



Between b and c. Fig. 546 (pretracheal and prevertebral layers), abscess would 

 spread most readily along the line of the trachea and in front of the vessels into the 

 superior mediastinum. 



In the intra-aponeurotic space (Space 2, Fig. 546) an abscess would probably 

 point superficially, as the fascia in front of it is very thin. If it were influenced by 

 gravity, however, it would follow the hyoid depressors and their intermuscular spaces 

 to the root of the neck, and might enter the superior mediastinum. 



Two additional and important spaces are formed by extensions or reduplications 

 of the cervical fascia. That portion of the superficial layer above the level of the 

 angle of the inferior maxilla, and passing from that bone to the zygoma, constitutes 

 the parotid fascia, which on the surface is continuous with that over the masseter, 

 while beneath it becomes thickened to constitute the stylo-maxillary ligament, sep- 

 arating the parotid and submaxillary glands and resisting overaction of the external 

 pterygoid muscle. As the outer fascial investment of 

 the gland is dense and resistant, and as internal to this Fig. 547. 



ligament the inner layer is .thinner and weaker than 

 elsewhere, — a positive gap existing between the styloid 

 process and the pterygoid muscle, — suppuration within 



the gland may result in extension to the retropharyngeal / '^, ^ Myio-hyoid muscle 

 region. It may follow the external carotid downward to 

 the chest, or, as the fascial investment is also incomplete 

 above, may extend upward to the base of the skull, or 

 even into the skull. It sometimes follows the branches ^ ' //-^-^^jJ-Hyoid bone 



of the third division of the fifth nerve through the fora- , / Outenayer offascia 



men ovale into the cranium. / inner layer of fascia 



The second space alluded to is formed by that por- Submaxillary gland 

 tion of the superficial layer between the jaw and the ^:,^^^Xo^S'rl^^^o::.^ic^. 

 hyoid bone and in front of the stylo-mandibular ligament, vicai fascia. 

 As it passes forward from the latter structure it splits and 



envelops the submaxillary gland, and becomes firmly attached below to the hyoid 

 and above to the lower jaw externally and the under surface of the mylo-hyoid 

 muscle internally (Fig. 547). Infection— " Ludwig's angina," "submaxillary 

 phlegmon," "deep cervical phlegm.on" — in this space, which contains the salivary 

 gland and its attendant lymphatics, is rendered exceptionally grave by the density 

 of these fascial layers. The infecting organisms — usually streptococci — may gain 

 access through a lesion of the floor of the mouth near the frenum, or from an alveo- 

 lar abscess, or by way of the digastric muscle from a focus of disease in the middle 

 ear. Once established, they, with their secondary products, are forced along the 

 lines of least resistance — by the side of the mylo'-hyoid usually — towards the base 

 of the tongue, involving the cellular tissue about the glattis and along the vessels 

 that perforate the fascia, causing infective venous thrombosis and involving the 

 deeper planes of connective tissue. Under the latter circumstances, if tension is not 

 promptly relieved, large vessels may be opened by the necrotic process. Jacobson 

 long ago called attention to the interesting fact that communications between ab-^ 

 scesses and deep vessels have usually taken place beneath the cervical fascia and 

 the fascia lata, two of the strongest fasciae of the body. 



Tiivwrs of the neck may originate in any of the diverse structures of that 

 region. It may be mentioned here "that their situation above or beneath the cervical 

 fascia is an important factor in determining their mobility, and hence the probable 

 ease or difficulty of their removal. In the latter situation associated pressure- 

 symptoms are common. 



