I 



MESENCEPHALIC ROOT 187 



slightly cephalad in the cerebellum incisions and slightly caudal in 

 the cerebrum incisions. Care was taken not to let the edge of the 

 chisel extend to the right of the median line, and the proper depth 

 was indicated by the notch on the blade of the chissl. Good results 

 were obtamed from both incisions, but with little or no danger 

 of injuring the trigeminal motor nucleus in the cerebellum in- 

 cision if it happened to be a little too deep. If any hemorrhage 

 resulted from the incision of the chisel, which in every case 

 extended from the median line to the left side, it was stopped 

 with a swab of hot sterile water. The left temporal muscle was 

 put back in place and its superficial fascia was sewed to the 

 superficial fascia of the right temporal muscle and the two flaps 

 of skin were joined, producing a double closure over the aperture 

 in the skull. A dressing of iodine was finally applied to the 

 wound. 



As in the previous experiments, the animals were allowed to 

 live fifteen days before killing them and removing their brains. 

 No infection occurred in any of these experiments, and it was 

 found after killing the animal that the hole in the skull had 

 completely ossified. Before removing a brain, all of the various 

 branches of the trigeminal nerve, the semilunar ganglion, and 

 the trigeminal roots from the left (lesion) side were care- 

 full}^ dissected away from the muscles and other structures, 

 but their attachment to the brain was left intact. In several 

 instances masseter muscle fibers were left attached to the masseter 

 nerve, to be sure of its identification in sections. 



After recovering from the shock of the operation, those animals 

 in which the brachium conjunctivum was little injured, behaved 

 exactly like normal animals. They would eat an equal amount 

 of lettuce and tough carrots as rapidly as normal animals. 



8. Results 



Four series of section have been cut from this material. Each 

 series included a part of the brain stem from a region a little 

 behind the entrance of the trigeminal sensory root to sections 

 passing through the cephalic end of the superior colhculus, with 



