REMOVAL OF THE BRAIN 



201 



to the external occipital protuberance posteriorly, and cut through the loose 

 areolar tissue and the pericranium in the same line down to the bone. 

 With the handle of the scalpel, or with a chisel, detach the pericranium from 

 the bone on each side and turn it posteriorly and downwards to the temporal 

 ridges, leaving the bone perfectly bare. Note that although the pericranium 

 is loosely attached over the surface of the various bones of the vault, it 

 is firmly attached along the lines of the cranial sutures by processes that 

 dip in between the bones and separate their edges. Detach the galea 

 aponeurotica and the temporal fascia from the temporal ridge on each side 

 with the edge of the knife ; then carrying the edge of the knife anteriorly and 

 posteriorly between the temporal muscle and the bone detach the upper 

 part of the muscle from the skull. When this has been done, each half of the 

 scalp can be turned down over the ear. 



The dissectors should next obtain a saw, a chisel, and a mallet, and 



Vein 



Sub-arachnoid space and trabeculae 



~~ ~ Dura mater 

 ^"~Subdural space 



Arachnoid 



Pia mater 



Fig. 82. Diagrammatic section through the Meninges of 



the Brain. (Schwalbe.) 

 co. Grey matter of cerebral gyri. 



proceed to remove the calvaria. The line along which the saw is to be 

 used may be marked out on the skull by encircling it with a piece of string, 

 and then marking the cranium with a pencil along the line of the string. 

 Anteriorly, the cut should be made fully three-quarters of an inch above the 

 margins of the orbits ; posteriorly, it should be carried round at the level of a 

 point midway between the lambda 1 and the external occipital protuberance. 

 The saw should be used to divide the outer table of the skull only. When 

 the diploe is reached, the sawdust will become red and moist, and the saw 

 should then be abandoned. The hammer and chisel are now brought into 

 requisition, and by short sharp strokes with these the inner table can 

 readily be split along the line in which the outer table of the cranium is 

 divided. When this has been done, insinuate the hook at the end of the 

 cross-bar of the chisel into the fissure in front, and wrench off the skull-cap. 



Dura Mater Encephali. The brain is clothed by three 

 distinct membranes, which are termed the meninges. These 



1 The term " lambda " signifies the apex of the occipital bone, or the point 

 at which the sagittal and lambdoidal sutures meet. 



