568 



PHYSIOLOGY 



CHAP. 



faradising the -pre-f rental cortex on the same side as the root 

 experimented on, a weaker inhibitory effect could also be observed 

 (Fig. 291). When, on the contrary, the occipital lobes of either 

 side were excited, even with very strong currents, no appreciable 

 alteration in the tracing could be detected. 



These researches show that inhibitory effects from cortical 

 excitation can be transmitted not only to the muscles of the fore-, 

 but also to those of the hind-limbs. 



Neither the experiments of Fano nor those of Oddi, however, 

 demonstrate that special inhibitory centres, antagonistic to the 

 motor centres, are contained in the cortex of the pre-frontal lobe. 

 The stimulus required to elicit inhibitory effects from this is always 

 stronger than that which elicits motor reaction when the excitable 



FIG. 290. Inhibitory effect of faradising pre-frontal lobe upon contractions of gastrocnemius 

 muscle of opposite side, excited by rhythmical stimulation of the fifth motor lumbar root. 

 (Oddi.) The middle line shows the beginning and end of the cortical excitation ; the lower 

 line indicates the rhythmical excitation of the spinal root. 



area is stimulated. The pre- frontal lobe contains no definite 

 and well-marked areas from which prompt and facile inhibitory 

 effects can be obtained. Oddi further observed that faradic 

 currents applied to the pre-frontal lobes after a marked inhibition 

 give rise to epileptic fits, probably because the stimulus is trans- 

 mitted to the motor area. All this tends to the conclusion (after 

 Bubnoff and Heidenhain, as above cited) that the centres contained 

 in the so-called motor area are capable of both motor and in- 

 hibitory reactions. 



Sherringtou (1893-95) and H. E. Bering and Sherrington (1897) 

 demonstrated that the faradisation of certain points of the cortex 

 lying in the motor area may, besides contraction, produce relaxa- 

 tion or depression of tone in the antagonist muscles. This effect is 

 obtained not on stimulating the same point of the cortex which 

 produces contraction, but on applying the stimulus to the area 

 which produces the contraction of the antagonists. There would 



