1893.] the Normal State of the Knee Jerk is altered. 441 



In the case of the cerebellum, a skin incision was made along the 

 middle line down the back of the neck, and at its upper extremity a 

 horizontal incision was carried across the vertex. The tissues were 

 then scraped and cut away, until the occipital bone and arch of the 

 atlas with the intervening occipito-atloid membrane were exposed ; 

 care being taken to work from the middle line outwards, as by this 

 means haemorrhage was found to be much less troublesome. When 

 the superior vermis, or part of it, was to be removed, the bone cover- 

 ing this region was removed by means of bone forceps, and then the 

 portion of the vermis desired excised by means of the knife. But 

 when one or other lateral lobe was to be removed the occipital bone 

 on that side was trephined by a half -inch trephine, and the opening 

 increased by means of bone forceps. The dura was next dissected 

 off, and then by means of a sharp scoop the lobe was scraped out. A 

 syringe containing hot water (about 100° F.) was used to aid in the 

 removal of the broken down cerebellar tissue, and in the arrest of 

 haemorrhage. The plan adopted in extirpating the labyrinth con- 

 sisted in making a curved incision, commencing above, passing 

 behind, and ending below the ear. The flap of skin with the pinna 

 was then turned forward, all structures divided and scraped from the 

 bone, so as to expose the meatus and the bone for a short distance 

 around. The upper and posterior part of the meatus was then 

 enlarged by means of a gouge, and by degrees the middle ear and 

 then the labyrinth were cut into and cleared out. 



When the 8th nerve was being exposed the skin incision varied 

 little from that described above ; but the bulla was more freely 

 denuded of its soft coverings. The bulla was opened by means of a 

 gouge, after which its inner wall was similarly cut through, until the 

 8th nerve was exposed. It was found that no appreciable length of 

 the nerve could be exposed without lifting up the lateral lobe of the 

 cerebellum, but that the nerve could be divided without interference 

 with this structure. This plan of operation was sometimes followed 

 in extirpating the labyrinth. 



In both these methods of operating, haemorrhage was profuse and 

 troublesome, but was checked by the use of aseptic wax. 



In those instances in which the animal was to be afterwards allowed 

 to live the operation was conducted on strict antiseptic principles, 

 the edges of the wound brought together by means of horse-hair 

 sutures, and the wound dressed antiseptically. 



In any instance where the operation was so severe as to lead one 

 to suppose that the animal would be conscious of pain after the effect 

 of the ether had passed off, a subcutaneous injection of J or 1 grain 

 of morphia was, as usual, given at the close of the operation, and 

 repeated if necessary. 



VOL. LIII. 



