x THE FOEE-BKAIN 567 



Fano determined the variations of the reflex time after 

 faradising the cortex. He observed that on exciting the pre- 

 frontal lobe for five seconds by an induction current (so strong as to 

 produce epileptoid convulsions when applied to the motor area), 

 there was invariably a depression of excitability in the cerebro- 

 spinal centres, lasting about three minutes. In. fact during this 

 time if the skin of the fore-limb of the opposite side were excited 

 by a break current, so as to provoke a reflex contraction from the 

 subjacent muscles, there was a reduction in the height of the 

 myographic curve, and a striking lengthening of the reflex period, 

 that is the contrary effect to that observed by Libertini after 

 excision of the pre-frontal lobe. 



FIG. 289. Inhibitory effect of weak cortical stimulation. (Bubnoff and Heidenhain.) At a the 

 muscle contracts, a a', after the application of a strong galvanic current to the cortical centre ; 

 at b there is a stronger contraction, 6 b', after a second excitation with same current ; after 

 the slow relaxation, b' c', the muscle is suddenly elongated, c' c, by the action of a weak 

 galvanic current on the same centre. 



Simultaneously with Fano, this cerebrospinal inhibition was 

 demonstrated by Oddi by a different method. He applied to the 

 5th ventral lumbar root a pair of electrodes, connected with a 

 sliding induction coil and a metronome which served as an inter- 

 rupter, so that the nerve could be rhythmically excited. The 

 rhythmic contractions of the gastrocnemius muscle were recorded 

 on a rotating drum. After exposing the brain under a suitable 

 degree of narcosis, he stimulated the cortex of the pre-frontal lobes 

 of the side opposite to the excited spinal root with another induced 

 current, arid noted profound changes of an inhibitory character on 

 the curves of the rhythmical contractions of the gastrocnemius 

 (Fig. 290). These inhibitory effects ensued after a fairly long 

 period of latent excitation, and continued for some time after the 

 application of the stimulus to the cortex had ceased. On 



