122 HODGE. [Vol. VII. 



of the right lower jaw, the opening being invariably made in 

 the left parietal bone. The probe will strike the floor of the 

 skull, having pierced the right optic thalamus and the right 

 crus. Work the probe across the floor of the skull about 3 mm. 

 to either side of its first position and withdraw it. Introducing 

 the probe again, direct it forward as before, but directly ventral, 

 aiming to pierce the left optic thalamus and left crus. Take 

 about one 3 mm. step with the end of the probe to right and 

 left, withdraw probe, and close the skin over the wound. The 

 purpose of the operation is, of course, to destroy sensibility in 

 the cerebrum and to cut off the sensory and motor tracts in the 

 crura ; and if successful, complete anaesthesia, with normal 

 pulse and respiration, should result. Remove the ether imme- 

 diately and allow the animal to recover. It should show no 

 signs of pain or distress, but should remain as though sleeping 

 quietly during the rest of the experiment. In some cases, how- 

 ever, the animal does beceme restless for a few minutes after 

 the ether passes off. This condition generally lasts but a short 

 time and gives place to the state of quiet sleep desired. After 

 this treatment stimulation may go on for any reasonable length 

 of time with no further trouble. I can recommend the method 

 to any who wish to make prolonged experiments not involving 

 the returning of the animal to consciousness. It is not, of 

 course, always successful. In some cases, the respiratory centre 

 becomes involved, spasmodic gasping sets in, and unless arti- 

 ficial respiration be employed, the experiment is at an end. 

 Examination has shown that this is due generally to hemorrhage 

 spreading downward from the section in the crura into the sub- 

 stance of the medulla or between the medulla and floor of the 

 skull. Consequently the probe should be so manipulated as to 

 injure the blood-vessels in the floor of the skull as little as 

 possible. 



The next step is to get the electrodes over the desired nerves ; 

 and, throughout the experiments, the nerves of the right bra- 

 chial plexus were employed. Turning the animal upon its back, 

 expose the external pectoral muscles by an incision through 

 the skin about two inches long midway between the sternum 

 and axilla. Cutting now through the pectoral muscles will ex- 

 pose the subclavian artery and vein, and just underneath these 

 can be seen the nerves of the brachial plexus. In order to pre- 



