72 Journal of Comparative Neurology. 



In 1 89 1 Cunningham (14, 338-9) said, that Guldberg had 

 suggested for the transinsular fissure "the very appropriate 

 name of snlais centralis insiilcB which indicates not only its 

 central position in the island of Reil, but also its relation to the 

 central fissure on the outer surface of the hemisphere mantle." 

 This author then endeavors to establish a connection between 

 gyres and fissures on either side of the transinsular with those 

 on the same side of the central fissure. He further states that 

 "it is true that we cannot regard these corresponding convolu- 

 tions and sulci as being directly continuous with each other but 

 still in many cases something which approaches very nearly to 

 continuity occurs. Thus it is well known that the inferior pre- 

 central sulcus, the fissures ot Rolando and the intraparietal sul- 

 cus are not infrequently carried downwards, so as to cut into 

 the fronto-parietal operculum and open into the Sylvian fissure," 

 There are many facts which seem to show that Guldberg and 

 Cunningham erred in their conception of the relation of these 

 two areas : 



1. The variations in the ventral extension of the central 

 fissure are believed to be due to individual difference. 



2. The connection of the central fissure with the Sylvian, 

 when it occurs, is almost always by a small, variable opercular 

 fissure (Cunningham 14, 341-2). Wilder, in 1894, in the report on 

 the brain of an educated suicide, having apparently duplicate 

 central fissures, says ((55^ 2): "On the left both centrals enter 

 the Sylvian, with a depth of at least 5 mm. On the right, the 

 first central approaches the precentral, the second joins the Syl- 

 vian at a depth of about 3 mm." So far as the writer has been 

 able to learn, this connecting fissure never completely divides 

 the operculum nor interrupts the circuminsular fissure in an 

 otherwise normal brain. 



3. The absence of the central fissure has not been shown 

 to produce an appreciable effect upon the transinsular and if 

 either is absent it is more often the central fissure. 



4. The insula is always sharply defined and is believed to 

 be a distinct lobe as sharply demarcated from the surrounding 

 areas as any lobe of the cerebrum, and the fissures and 



