M. R. COVIAN, C. TIMO-IARIA AND R. F. MARSEILLAN 



439 



very high voltage reticiUar stimulation (<S volts) was used did both waves 

 disappear, as shown in Figs. 9 and 10 in superimposed sweeps at 100 and 

 50 msec, interval. 



Control cxpcriiiiciits. The possibility of spreading current to the medial 

 lemniscus was ruled out by the following experiment: a concentric 

 electrode was placed on the medial lenniiscus at co-ordinates As, L5, H3. 

 Its stimulation determined an evoked potential in the cerebral cortex. 



2v 



3v 



5v 



Fig. 8 

 Voltage series at 50 msec, interval. Time 200 cps. Calibration: 500 liV. 



While the evoked potential in somatosensory area was being recorded by 

 stimulation of the forepaw in the usual way, electrolytic lesions were made 

 by a 5 mA direct current until the evoked potential disappeared. At this 

 point the stimulation of the medial lemniscus did not evoke any potential 

 in the cerebral cortex, but the stimulation of the brain stem reticular 

 formation at co-ordinates A3, L2.5, H2 evoked a cortical pcnential as 

 before. This evoked potential by single shock reticular stimulation was 

 very similar to that obtained in the same conditions by Buser and Borenstein 



