FISSURE OF ROLAXDO 



683 



The frontal operculum is the small part of the inferior frontal convolution inclosed 

 between tlie iiscenilintr and the anterior horizontal limbs of the Sylvian fissure and 

 the orbital operculum is the part of the interior frontal convolution beneath the 

 latter liml). 



The fissure of Rolando, or central sulcus, serves as a line of demarcation 

 between the frontal and parietal lobes. It is. next to the fissure of Sylvius, the 

 most important of the ineomi)lete fissures of tlie brain. It extends from the great 

 longitudinal fissure to the Sylvian fissure, and may connnunicate Avith the latter 

 (19 per cent., Cunningham), but the comnumication is always shallow. At its 

 upper end it usually (GO per cent, Cunningham) passes into the great longitu- 

 dinal fissure and ap})ears on the mesial surface of the hemisphere, where it ends by 

 l)ending backwards for about a quarter of an inch. The fissure of Rolando is 

 directed downwards and forwards so that the fissures of the two sides taken 

 together form an angle of about 143°, open in front. The fissure does not pursue 

 a perfectly straight course, but is somewhat sinuous, and two of its bends, more 



Fig. 410. — Lateral View of the Fisskees axd Coxvolutioxs of the Cerebeum. 



AscEynrxo 



PARIETAL 



coyvoLUTioy 



SUPERIOR 

 PR.'E- 

 FISSVRE OF CEXTRA L 

 ROLAXDO FISSCRF 



ASrEXDIXG 

 FliOXTA L 

 rnxvOLL'TIOX 



SUPERIOR 

 FRO XT A L 

 FISSURE 



IXTRA PA RI- 

 ETAL FISSURE 



SUPERIOR 

 PARIETAL 

 LOBULE 

 SUPRA- 

 .VARGIXAL 

 COX VOL 



ASai-LAR 

 AST) rosT- 

 PARIETAL 



(iYRI 

 EXT ER SAL 

 PAKIETO- 



orrrp/TAL 

 F/.isrRE 



SCPBRKJR 

 OCCIPITAL 



coyroLr- 



TIOS 



TRA \.<- 



VERSE 



OCCIPITAL 



FISStRE 



IXFERIOR 



OCCIPITAL 



COS VOL r- 



TIOS 



SUPERIOR 



FROXTAL 



rOXV0LUTI0:i 

 IXFERIOR 



FROXTA L 



FISSURE 



MIDDLE 

 FROSTAL 

 COSVOLC- 

 TIOS 



PR.K-()< ilPlIAL SULCUS 



XOTCH OCCIPITALIS 

 ANTERIOR 



SUPERIOR 



TE.VPORA L 



FISSURE 



Mii'iuj-: 



TEMPORA L 



FISSURE 



ISFERIOR 

 FROSTAL 

 COS VOL L-- 

 TIOS 



ORBITAL SURFACE 

 •I ULRIon TEMPORAL 

 COXVOLUTIOX 

 MIDDLE TEM- 

 \ PtiR \L COXVOLUTIOX 

 JXFERIOR 

 TEMPORA L 

 COXVOLUTIOX 



conspicuous and constant than the others, have been described as the superior and 

 inferior genua. These genua mark off the fissure into three api^roximately equal 

 l)arts. The superior genu is directed backwards. The inferior genu looks 

 forwards; it is more constant and much more strongly marked than the superior 

 genu. In rare cases the fissure of Rolando may communicate with the prsecentral 

 or intraparietal sulci, but as a rule it pursues an isolated course across the convex 

 surface. 



It has been very generally taught that the fissure of Rolando is caused by the jiressure of a 

 vein which pa.sses during foetal life (from the fliurth to the sixth month) from the middle cerebral 

 vein to the superior longitudinal sinus. This view has been recently disproved, as it has been 

 shown that the fi.ssure develops in two segments, an upper and a lower, and the fissure is after- 

 wards completed by the sinking down of the central portion. The remains of this central eleva- 

 tion can always be seen on opening the fissure of Rolando as a deeply placed ainiectant or bridging 

 convolution at the level of the superior genu. (Cunningham.) 



The fissure of Rolando is one of the earliest of the incomplete fissures to appear, and is 

 usually developed during the last week or ten days of the fifth month of intra-uterine life. By 

 its transverse direction it interrupts the longitudinal course of the majority of the cerebral fissures ; 



