. Anatomy, descriptive and applied. Anatomy. 918 THE NERVE SYSTEM tion of the opercula leaves a triangular space. This space is usually obliterated in childhood, but is commonly met with in certain races (negro, Australian) and in brains showing developmental defects or arrest. The mechanics of the formation of the surface outline of the sylvian fissure by the apposition of the growing and plastic opercula may be understood by a reference to Fig. 682. POSTCENT. INTERLOCKING Fig. 677.—Central fissure fully opened up, so as to exhibit the interlocking gyres. The central fissure {fissure of Rolan
. Anatomy, descriptive and applied. Anatomy. 918 THE NERVE SYSTEM tion of the opercula leaves a triangular space. This space is usually obliterated in childhood, but is commonly met with in certain races (negro, Australian) and in brains showing developmental defects or arrest. The mechanics of the formation of the surface outline of the sylvian fissure by the apposition of the growing and plastic opercula may be understood by a reference to Fig. 682. POSTCENT. INTERLOCKING Fig. 677.—Central fissure fully opened up, so as to exhibit the interlocking gyres. The central fissure {fissure of Rolando [sulcus ce7itralis]) is situated at about the middle of the convex surface, and, coursing obliquely laterofrontad, divides this surface into approximately equal parts, intervening between the frontal and parietal lobes. It may be traced from a point at or near the dorsimesal border, about' 1 cm. (f inch) caudad of the mid-point of the occipitofrontal arc. It then runs sinuously laterofrontad to within a short distance of the sylvian fissure, about 2 cm. (A inch) caudad of the sylvian point; its line of general direction makes an angle of about 70 degrees with the median line (Rolandic angle). If measured ?along its sinuosities, its length averages cm. (4 inches). Its curved course may be analyzed into five alternate curves (sometimes more or less), of which three are convex frontad and two caudad. It is rarely very much branched and does not often anastomose with neighboring fissures. Its dorsal end bears a con- stant relation to the caudal limb of the paracentral, frontad of which it can be found as a hook-like curve (Figs. 676 and 679). If the lips of the central fissure be divari- cated, interdigitating sub-gyres are commonly seen in its depths (Fig. 677). These interlocking gyres are often fused to a greater or less degree, and a total interruption of the fissui-e has, in rare instances, been observed. The central fissure develops at about the end of the fifth mon
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
