THE BRAIN. 



SUBSIDIARY FISSURES AND CONVOLUTIONS. 



The precentral and postcentral sulci are about 15 mm. (f in.) anterior 

 and posterior to the fissure of Rolando. 



The inferior frontal convolution lies between the line of the fissure of 

 Sylvius below and a line just below the temporal ridge above. 



The middle frontal convolution lies under the frontal eminence, and occu- 



Central fissure or 

 fissure of Rolando 



Line for central or 

 Rolandic fissure 



Precentral sulcus 



Interparietal 

 sulcus 



Parieto-occipital fj| 



fissure 



Transverse occip- 

 ital sulcus 



Parietal eminence-'' 



Lateral occipita 

 sulcus 



Posterior horizontal limb of 

 Sylvian fissure 



Line for Sylvian fissure 



Temporal ridge 

 Ascending limb of 

 Sylvian fissure 

 Anterior horizontal limb 

 Main portion of 

 Sylvian fissure 

 -Glabella 



FIG. 50. Semidiagrammatic view of head, showing relation of Rolandic and Sylvian fissures and lines. 



pies about the lower two-thirds of the distance between the temporal ridge below 

 and the midline above. 



The superior frontal convolution covers about the upper one-third of the 

 distance from the median line above to the temporal ridge below. 



The superior frontal sulcus passes upward from the supra-orbital notch. 



The inferior frontal sulcus runs just below the temporal ridge. 



The first or superior temporal convolution runs along the lower side of 

 the fissure of Sylvius. It is about 15 mm. (- in.) wide. 



The first or superior temporal sulcus or parallel fissure runs parallel to 

 the Sylvian fissure and 15 mm. below. 



The second or middle temporal convolution is wider than the first and lies 

 a short distance above the level of the base of the skull. 



The middle temporal sulcus runs close above the zygoma. 



The third or inferior and the fourth temporal convolutions lie on the base 

 of the brain, separated by the inferior temporal sulcus. The fourth temporal convo- 

 lution has on its inner side the collateral fissure (see Fig. 42). 



The interparietal sulcus (pars horizontalis) leaves the postcentral sulcus 

 near its middle and passes upward and backward to a point opposite the lambda. 



The supramarginal convolution surrounds the termination of the fissure of 

 Sylvius and is, therefore, under the parietal eminence. 



