145 



On Postural and Non-Postural Activities of the Mid-Brain. 

 By T. Graham Brown (Carnegie Fellow). 



(Communicated by Prof. C. S. Sherrington, F.R.S. Received July 21, 1913.) 



(From the Physiological Laboratory of the University of Liverpool.) 



CONTENTS. 



PAGE 



I. Introduction 145 



II. Methods Employed 146 



III. The State of the Monkey after Decerebration 147 



IV. Electrical Stimulation of Eegions in the Cross-section of the Mid- 



brain Dorsal to the Area of the Cortico-spinal Tract 148 



1. The Ipsilateral Eeaction 148 



2. The Contralateral Eeaction 148 



3. The Synchronous Compounding of Ipsilateral and Contra- 



lateral Eeactions 149 



4. The Compounding of Ipsilateral and Contralateral Eeac- 



tions in Temporal Succession 154 



5. The Geographical Position of the " Focal Point" 154 



V. The Effect of Various Lesions 155 



1. Mesial Section between the Eight and Left Halves of the 



Mid-brain 155 



2. Eight Semi-section of the Mid-brain between Anterior 



and Posterior Colliculi 155 



3. Division of the Eight Superior Cerebellar Peduncle 155 



4. Complete Eemoval of the Cerebellum 155 



5. Eemoval of Mid-brain 156 



VI. Electrical Stimulation of the Crus Cerebri 158 



VII. Compound Stimulation of Crus and the more Dorsal Excitable 



Area in the Cross-section of the Mid-brain 158 



1. Immediate Compounding of Crus against Contralateral 



Eeaction (Extension) 159 



2. Immediate Compounding of Crus against Ipsilateral 



Eeaction (Flexion) 159 



3. Compounding in Temporal Succession 159 



VIII. Stimulation of other Points in the Mid-brain and Hind-brain 159 



IX. Conclusions 161 



I. Introduction. 



In the course of experiments in which the cerebral cortex of the monkey 

 is stimulated, it is peculiarly noticeable that the activity of the cortex varies 

 from time to time. That such variation should occur is by no means 

 strange, in view of the difficulty of maintaining a constant depth of narcosis. 

 But there are other variations which seemingly are not conditioned by 



