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Diagram to illustrate the development of the opercula which cover the insula. A, Sylian fossa before opercula begin to form. B, Fronto-paretal and temporal opercula wells advances. C, All the four opercula developed but not in opposition. Labels: F.P., fronto-parietal operculum; T, temporal operculum; F.R., frontal wall of fossa; O.R., orbital wall of fossa; F., frontal operculum; O, orbital operculum; s2, anterior horizontal limb of Sylvian fissure; s3, ascending limb; s4, posterior horizontal limb.

Development of the Opercula

Diagram to illustrate the development of the opercula which cover the insula. A, Sylian fossa before…