APPLIED ANATOMY. 



skin and aponeurosis. The aponeurosis beneath is intact, therefore the pus does 

 not get below it. The cyst, with the lining membrane entire, should be removed, 

 otherwise it will recur. 



2. Subaponeurotic abscesses come from infected wounds, erysipelas, or caries of 

 the bones. It is not desirable to close deep wounds of the scalp too tightly. Some 

 suppuration is liable to occur which, not finding an easy escape externally, may 

 spread under the aponeurosis if the wound has been deep enough to divide it. 

 Infection of wounds is the most frequent source of these abscesses, hence the desira- 

 bility of providing for drainage for at least a short period. In erysipelas, serous 



effusion, which may become purulent, oc- 

 curs in the subaponeurotic tissue, as well as 

 in the layers above. It may sink down- 

 ward and point in the temporal, occipital, or 

 frontal region. In the temporal region the 

 descent of the pus may be limited by the 

 attachment of the lateral expansion of the 

 aponeurosis to the zygoma. The attachment 

 of the occipitalis muscle posteriorly to the 

 superior curved line of the occiput prevents 

 the effusion from coming to the surface at 

 that point. The liquid accumulates low down 

 on the forehead over the orbits, being pre- 

 vented from entering by the attachment of 

 the orbitotarsal ligament, and tends to point 

 close to the median line. The frontal muscles 

 of the two sides are apt to be slightly sep- 

 arated, leaving a weak spot just above the 

 root of the nose, and this is where fluctua- 

 tion can most easily be felt. These accumu- 

 lations in the frontal, temporal, and occipital 

 regions may require incisions for their evac- 

 uation and drainage. Suppuration arising 

 from carious bone readily perforates the 

 pericranium and then infiltrates the loose 

 subaponeurotic tissue. The bones of the vault of the skull are not infrequently 

 affected by syphilitic disease, producing caries and suppuration, which invade the 

 subaponeurotic space. 



3. Subpericranial abscesses are comparatively rare. They usually start from 

 diseased bone and spread laterally beneath the pericranial tissue. The pus may be 

 limited to a single bone on account of the firmer attachment of the pericranium at the 

 site of the sutures. To avoid breaking into the subaponeurotic space, a free opening 

 should be made into the abscess so as to allow the pus to drain externally. 



AFFECTIONS OF THE BLOOD-VESSELS. 



The arteries or veins alone may be affected, or both may be involved. 



Arterial varix is the name given to an enlargement of a single artery. It forms 

 a swollen, tortuous, pulsating mass in the course of the artery. The temporal artery 

 is liable to be so affected, particularly its anterior branch. 



Cirsoid aneurism, or aneurism by anastomosis, is formed by numerous enlarged 

 arteries. It is sometimes called an arterial angioma or plexiform angioma. The 

 veins are also somewhat involved. Pulsation is marked. 



Venous angioma is a tumor formation in which the venous blood is contained in 

 large spaces, which are lined with endothelium, instead of in normal veins. 



Telangiectasis or ncevus is formed of enlarged capillaries. It is often called 

 port wine mark, mother's mark, etc. 



Aneiirismal varix, or arteriovenous aneurism, is where an adjacent artery and 

 vein being wounded, as the temporal artery and vein, the blood passes directly 

 from the artery into the vein. 



FIG. 8. Arterial angioma or cirsoid aneurism. 



