DISSECTION OF THE HEAD AND NK< K 197 



from fat, between it and the pericranium. The presence of this 

 layer (1) permits of freedom of movement of scalp, (2) accounts 

 for extensive effusion of blood which may follow scalp injury, 

 and (3) explains wide distribution of pus or other inflammatory 

 products in infections involving the tissue beneath the M. epi- 

 cranius (hence the term " dangerous area of the scalp "). 



Lymphatics of the Scalp. (Cf. Toldt, Fig. 1085; also Poirier et 

 Charpy, t. ii., fasc. iv., p. 1282, Fig. 630.) 



Try to find the- 



(a) Occipital lymph-glands (lymphoglandulae occipitales) . These are of 



significance in the diagnosis of syphilis, pediculosis, and other con- 

 ditions. 



(b) Posterior auricular lymph-glands (lymphoglandulae auriculares pos- 



terior es). 



(c) Anterior auricular lymph-glands (lymphoglandulae auriculares an- 



teriores). 



OPENING THE CAVITY OF THE SKULL. 



Nowadays the brain is usually removed immediately after 

 the cadaver is turned over to the department of anatomy, in 

 order that it may be better prepared in formalin for subsequent 

 study. Occasionally, however, a cadaver with the brain still 

 in situ arrives in the dissecting-room; and in any case the student 

 should know how to remove a brain. 



Raise the head of the cadaver by means of a wooden block. 

 Make a coronal or frontal section, with a cartilage-knife, from 

 the region behind the left ear, transversely over the vertex, to the 

 same region behind the right ear. The cut should go through 

 the galea aponeurotica down to the pericranium. Turn the front 

 flap downward over the face and the hind flap downward over 

 the neck. The temporal fascia and temporal muscle should be 

 separated from the bone and reflected downward. Now make a 

 horizontal cut with the saw along the largest horizontal cir- 

 cumference of the skull ; the saw passes through the glabelln in 

 front and a little above the protuberantia occipitalis cxtcrna 

 behind. Saw through the outer table of the skull only. With 

 hammer and chisel split the inner table along the line of the cut. 

 Insert a hook into the cut in front and forcibly wrench off the 

 skullcap. The outer surface of the dura mater is now exposed. 



