MOTOR FUNCTIONS OF CEREBRAL CORTEX OF CAT 179 



median fissure and on the under surface of the hemisphere it 

 almost meets the optic chiasm. Its outer margin, the fissura 

 rhinalis, curves downwards, then gradually outwards, and reaches 

 the supraorbital fissure. The latter begins 5 mm. underneath 

 the middle of the crucial sulcus, and is directed downwards, and 

 backwards, to meet the fissura rhinalis. (The description of 

 other features of the cat's brain will be found in Wilder and 

 Gage.) 



Running parallel with the superior margin of the hemisphere, 

 and about 5 mm. from it, is the fissura lateralis (F.L.), extending 

 from the posterior portion of the superior surface forwards to a 

 point about 7.5 mm. above the outer end of the crucial sulcus, 

 then turning sharply inward toward the inner end of the crucial. 

 At the point where it changes its direction, the ansate fissure 

 arises and extends outwards and forwards for about 2.5 mm. 

 At or near the outer end of this fissure the fissura coronalis 

 starts and travels in a semi-circular course around the outer end 

 of the crucial sulcus, having a radius of about 0.5 cm. from the 

 end of the crucial. A small dimple, sometimes a short fissurette 

 as it is called by Campbell, is found at a point about equally 

 separated from the outer half of the sulcus cruciatus and the 

 fissura lateralis. This it is that Campbell believes to be the 

 "homologue of Rolando/' i.e., the upper half of the fissure of 

 Rolando, although it may be stated that this belief is not in 

 keeping with the physiological findings of the present work. 

 When distinguishable as a fissure, it is called the compensatory 

 ansate fissure. 



Histologically, Campbell and others have found that the so- 

 called motor area contains fiber and cell arrangements, which 

 map it off rather sharply from surrounding areas. Campbell's 

 studies have led him to conclude 'that the motor area in the cat 

 may be represented as in the accompanying figures (fig. 2) . He 

 describes this area as follows: 



On the mesial surface, the area is confined to a small portion of the 

 marginal gyrus, situated immediately behind the sulcus cruciatus, and 

 it is worthy of mention that it does not reach quite to the hinder ex- 

 tremity of the sulcus. In a frontal view, the close relation to the sul- 



