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HUMAN PHYSIOLOGY. 



Secondary fissures of importance are found in different lobes of the cere- 

 brum, separating the various convolutions. In the anterior lobe are found the 

 precentral, superior frontal, and inferior frontal fissures; in the temporosphe- 

 noid lobes are found the first and second temper osphenoid fissure; in the occipi- 

 tal lobe, the cakarine and hippocampal fissures. 



Convolutions. Frontal Lobe. 



The ascending frontal orprecentral convolution, situated in front of the fissure 

 of Rolando runs downward and forward; it is continuous above with the 

 anterior frontal, and below with the inferior frontal, convolution. 



FIG. 25. DIAGRAM SHOWING FISSURES AND CONVOLUTIONS ON THE LATERAL 



ASPECT OP THE LEFT HEMI-CEREBRUM. 



F. Frontal. P. Parietal. T. Temporal and O. Occipital lobes. S. Fissure of 

 Sylvius. E P S. Epi-sylvian. PRS. Pre-sylvian. S B S. Sub-sylvian fissures. C. 

 Central fissure or Fissure of Rolando. P R C. Pre-central fissure. S P F R. Super- 

 frontal fissure. M E F R. Medi-frontal fissure. S B F R. Sub-frontal fissure. P C. P C. 

 Post-central fissure. PTL. Parietal fissure. PAROC. Par-occipital, EXOCC. 

 Ex-occipital fissures. SPTMP. Super-temporal fissure. MTMP. Medi-temporal 

 fissure. 



The superior frontal convolution is bounded internally by the longitudinal 

 fissure, and externally by the superior frontal fissure; it is connected with the 

 superior end of the frontal convolution, and runs downward and forward to 

 the anterior extremity of the frontal lobe, where it turns backward, and rests 

 upon the orbital plate of the frontal bone. 



The middle frontal convolution, the largest of the three, runs from behind 

 forward, along the sides of the lobe, to its anterior part; it is bounded above 

 by the superior and below by the inferior frontal fissures. 



The inferior frontal convolution winds around the ascending branch of the 

 fissure of Sylvius, in the anterior and inferior portion of the cerebrum. 



