INTRACRANIAL 361 



(a) Subdural. 



1. Anaesthetise the animal and secure it to the oper- 

 ating table, dorsum uppermost. 



2. Shave a portion of the scalp immediately in front 

 of the ears. 



3. Mark out with a sharp scalpel a crescentic flap 



FIG. 187. Guy's electrical dental engine. 



of skin muscle, etc., convexity forward, commencing 

 0.5 cm. in front of the root of one ear and terminating 

 at a similar spot in front of the other ear. Reflect the 

 marked flap. 



4. Make a corresponding incision through the perios- 

 teum and raise it with a blunt dissector. 



5. With a small trephine (diameter 6 mm.) remove 

 a circular piece of bone from the parietal segment. 

 The centre of the trephine hole should be at the inter- 

 section of the median line and a line joining the pos- 

 terior canthi (Fig. 1 88). 



6. Introduce the inoculum by means of a hypo- 

 dermic syringe, perforating the dura mater with the 

 needle and depositing the material immediately below 

 this membrane, at the same time taking care to avoid 

 injuring the sinuses. 



