402 Anatomy Applied to Medicine and Snrgety. 



ducts spreading beneath it. Should septic processes de- 

 velop in the wound, the laxity of the attachment of this 

 epicranial aponeurosis to the pericranium, allows the pus 

 to burrow beneath the aponeurosis and thus separate these 

 structures, so that the whole of the scalp may be 

 raised from the skull as though it rested on a 

 water-bed. When this occurs the swelling is es- 

 pecially marked, through the influence of gravity, in 

 front, above the orbits ; behind, above the superior curved 

 line of the occipital bone, and, laterally, above the 

 zygoma and the mastoid, and at these points, especially in 

 front and behind, openings for the exit of the purulent 

 collection may be made. It follows then, that, in wounds 

 involving the epicranial aponeurosis, the strictest applica- 

 tion of asepsis should, as in all other wounds, not be de- 

 viated from. Cephalhtzmatoma, or blood tumor, may be 

 the result of blows or falls, or may result in the new born 

 from pressure on the head of the child during labor. In 

 it the collection of blood may be present (1) in the super- 

 ficial tissues of the scalp, i.e., superficial to the aponeu- 

 rosis; (2) beneath the aponeurosis itself; (3) underneath 

 the pericranium. In some of these cases of cephalhaema- 

 tomata, the sensation imparted to the examining finger re- 

 sembles somewhat that from a depressed fracture, since 

 they both present a hard edge with a central depression, 

 but, in the case of the blood tumor, firm pressure on the 

 edge of the tumor for a moment or two will cause the 

 raised edge to disappear and the bone to be felt under- 

 neath, whereas, such pressure in fracture will have no 

 effect. MacEwen's explanation of this peculiar shape of 

 some of the cases of blood tumor is, that the inflicting 

 blow causes disintegration and scattering of the cellular 

 elements at the part struck, with a corresponding heaping 

 up, at the margin of the area, which, along with the infil- 



