154 APPLIED ANATOMY. 



teeth, suppuration of the thyroid gland, and other causes. They may have their 

 course influenced by the various layers of the deep fascia. 



Pus in the Submaxillary Region. As the submaxillary space has the mylo- 

 hyoid muscle as its floor, abscesses here show below the body of the mandible 

 between it and the hyoid bone. Usually they point towards the skin. Infection of 

 this space may occur from the teeth. Tillmans ("Surgery," vol. i, p. 434) saw a 

 case in which in four days the pus caused death from infection of the mediastinum 

 and pleura. This proceeded downward from a badly extracted tooth and thence 

 under the deep fascia of the neck to the chest. 



The pus, filling the submaxillary space, as can also occur in Ludwig's angina, 

 which is an infective inflammation of the submaxillary and sublingual regions, may 

 follow the lingual and facial arteries to the sheath of the great vessels and down into 

 the superior mediastinum. The infection in Ludwig's angina may pass around 

 the posterior edge of the mylohyoid muscle and involve the structures around the 



Buccinatoi 



Masseter 



Internal pterygoid 



Buccopharyngeal 

 fascia 



Retro pharyngeal 

 space 



Prevertebral fascia 



Rect 



Posterior pillar 



of fauces 



External carotid artery 



Parotid gland 

 Internal jugular vein 



Longus colli 



Vagus nerve 

 Internal carotid artery 



FIG, 179. Section through the upper portion of the third cervical vertebra, showing the buccopharyngeal and 

 prevertebral fascias and retro pharyngeal space. 



base of the tongue and pharynx, and produce cedema of the larynx and death (see 

 page 200). 



Pus superficial to the deep fascia tends to perforate the skin and discharge 

 externally. If it is slow in forming it may sink down and pass over the clavicle 

 onto the upper portion of the chest. 



Pus in the suprasternal notch or space of Burns bulges anteriorly but may 

 perforate posteriorly. The sternothyroid and sternohyoid muscles are attached to the 

 posterior surface of the sternum ; but the layer of fascia on their anterior surface is 

 very thin, so that pus may either pass between the muscles or perforate them and so 

 pass down in front of the pretracheal fascia close to the under surface of the sternum. 

 It would then tend to show itself in the upper intercostal spaces, close to the 

 sternum. 



Pus between the pretracheal and siiperficial layers, as may occur from abscesses 

 of the thyroid gland, tends to work its way downward rather than laterally. The 

 pretracheal fascia at the sides blends with the sheath of the vessels and the fascia 

 covering the posterior surface of the sternomastoid muscles. In this space lie the 

 sternohyoid, sternothyroid, and omohyoid muscles. The pretracheal fascia is beneath 

 them and the superficial layer of the deep fascia above. Pus can follow the posterior 



