OF DENISON UNIVERSITY. jq 



Nearly the whole upper surface of the cerebral hemisphere of the 

 left side was exposed. The loss of blood was very moderate. 



The electrodes were introduced at point i, Ftg. 2, IMate XI, about 

 9 mm. from the median fissure and a little in advance of the line pass- 

 ing through the anterior angle of the eye. The result was a forward 

 and inward motion of the right fore leg. 



At point 2, the introduction of the electrode gave an undefined 

 movement of right fore leg. 



At point 3, about 7 mm. from the median line and separated from 

 I by a faint sulcus, the stimulation jjroduced a flexion of the pes on 

 the crus and elevation of right hind leg. 



At 4, a movement of the right hind leg, as at 3, and a slight ro- 

 tation of the fore leg inwards. 



At 5, about 3 mm. from the median line, the stimulation pro- 

 duced an extension and divarication of the digits of the right foot. 



At 6, the fore leg was elevated and flexed, and with a little stronger 

 current the hind leg was also elevated and flexed. 



At 7, there was an extension of the toes corresponding to the 

 movements produced at 5, of the opposite side. 



Perhaps more important in its bearing on the jjresent subject is a 

 set of experiments upon the opossum, of which, unfortunately, no very 

 exact data have been preserved. The configuration of the hemispheres 

 as well as the details of structure resemble very closely those of rodents. 

 Moreover, such hints as we have of the development of the Rodentia 

 indicate a common origin for the two groujjs and comi)aralively slight 

 subsequent differentiation. It, then, would not be surprising if a con- 

 siderable similarity of distribution in the cortical elements should l)c 

 proven to exist. On the other hand, the existence of an ajjparent 

 homologue of the crucial sulcus near the front of the cerebrum would 

 lead one to expect the aggregation of the motor elements near this 

 sulcus. The experiments in this case were made with a (Jrenel cell 

 and DuBois-Raymond coil, with the .secondary coil at about S cm . the 

 current being applied l)y a i)air of platinum electrodes separated by 

 about 3 mm. Stimulation of the region about the crucial sulcus (so 

 called) resulted in movements ot the anterior extremity, but the diffi- 

 culty in controlling the flow of blood interferred with close analysis. 

 The area on either side of the median fissure responded with various 

 poorly localized contractions of the trunk. About 6 8 mm. posterior to 

 the crucial sulcus and 4-5 mm. from the medial line is an ill-defined 



