MOTOR FUNCTIONS OF CEREBRAL CORTEX OF CAT 217 



the motor cortex by associational fibers; (b) there may be mutual 

 connections of the two regions by means of fibers running to the 

 basal ganglia, such as the lenticular, or the caudate nuclei, or 

 the optic thalamus; (c) efferent fibers passing to the cerebellum, 

 from the two regions, may mediate the control there; (d) efferent 

 fibers, from the extra-motor regions, passing into the spinal 

 cord to the spinal cell centers, may be responsible. 



It seems most likely that the extra-motor influence is like 

 that of the efferent elements in the spinal cord upon the activity 

 and tonus of muscles, innervated by cells in corresponding spinal 

 segments. 



COMPARISON OF THE PERIOD OF LATENCY FROM STIMULATION OF 

 POINTS ON THE CORTEX AND POINTS JUST UNDER THE CORTEX 



In three animals stimuli were applied to various points on the 

 cortex within the motor area, and records were made of the re- 

 actions. From these there were determined the tunes between 

 the beginning of the stimulation and the resulting movements, 

 i.e., the latent periods. After these records were made, for 

 each of the points chosen, the cortex at that particular area 

 was removed with a sharp pair of hair-pointed scissors and as 

 soon as the slight hemorrhage was controlled, the tissue under- 

 neath was similarly stimulated to determine if there was a 

 change in the duration of this period. The tissue removed was 

 about 2 mm. square and of about the same thickness. The 

 time interval was unfortunately not measured in terms of 

 seconds or parts of seconds, but in terms of vibrations of the 

 primary coil of the inductorium, which was used for stimula- 

 tion. While it is not certain that this vibration remained con- 

 stant in all tests, it is certain that it was reasonably constant 

 for the tests on each animal. The comparison of the latencies 

 is, therefore, possible although not in parts of a second. The 

 following table (table 7) gives the results of these tests. On 

 the brain of each animal the number of stimulable points differed, 

 and at times more subcortical than cortical stimuli were given 

 at one point. The table shows the number of stimuli, the aver- 



