486 Anatomy Applied to Medicine and Surgery. 



of the cervical fascia, as would occur if the pus were be- 

 neath this fascia. In the latter case, if the abscess 

 be beneath the superficial portion of the deep fascia at the 

 side of the neck, it may, passing beneath the clavicle, bur- 

 row into the axilla. Should the collection be beneath the 

 same fascia in the front of the neck, it would, lying be- 

 tween this layer and that covering the depressors of the 

 hyoid bone, be directed into the anterior mediastinum. If 

 it lie beneath the pretracheal layer it would follow this 

 layer downwards, and since the pretracheal is continuous 

 with the fibrous portion of 'the pericardium, would ap- 

 pear in the middle and posterior mediastina ; while, if be- 

 neath the posterior or prevertebral layer, it could burrow 

 into the axilla, sinice a process of this layer surrounds the 

 subclavian artery, or it could gravitate to the posterior 

 mediastinum. 



Pressure Effects of Aneurism of the com- 

 mon carotid. In aneurism involving the arteries of 

 the neck the common carotid is most frequently affected, 

 and, when so, the tumor develops near its bifurcation, as a 

 rule, and any oif the following symptoms may be present 

 as the result of pressure by the tumor : (1) On the inter- 

 nal jugular cyanosis of the face, passive congestion of 

 the brain and headache; (2) on the pneumogastric -dis- 

 turbance of the stomach, such as vomiting, etc., or of the 

 lungs, asthmatic attacks ; or of the heart, interference 

 with the rhythm, or change of blood pressure. Should 

 the tumor extend higher up the neck than the point of bi- 

 furcation, it may compress the superior laryngcal branch, 

 with production of cough or spasm or of paralysis of the 

 crico-thyroid muscle ; or, if it involve the lower or middle 

 portions of the artery, the recurrent laryngcal might be 

 compressed, producing hoarseness and difficulty in speak- 

 ing; (3) pressure on the decendens noni will cause weak- 



