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TEXT-BOOK OF PHYSIOLOGY. 



5. The calcarine fissure begins on the posterior extremity of the 



mesial surface of the occipital lobe. From this point it passes 

 downward and forward to unite with the parieto-occipital 

 fissure. 



6. The calloso-marginal fissure is a deep cleft on the mesial surface 



of the hemisphere. It begins below the anterior extremity of the 

 corpus callosum and in a general way follows the course of this 

 structure as far as its posterior extremity, where it turns upward 

 to terminate at the margin of the hemisphere just posterior to 

 the fissure of Rolando. 



FIG. 221. DIAGRAM SHOWING FISSURES AND CONVOLUTIONS ON MESIAL ASPECT 

 OF THE RIGHT HEMISPHERE. Median aspect of the right hemisphere. CC. 

 Corpus callosum divided longitudinally. Gf. Gyrus fornicatus. H. Gyrus hip- 

 pocampi, h. Sulcus hippocampi. U. Uncinate gyrus. cm. Calloso-marginal 

 fissure. F. First frontal convolution, c. Terminal portion of fissure of Rolando. 

 A. Ascending frontal, B. Ascending parietal, convolution and paracentral lobule. 

 P/. Precuneus or quadrate lobule. Oz. Cuneus. Po. Parieto-occipital fissure. 

 0j. Transverse occipital fissure, oc. Calcarine fissure, oc'. Superior, oc". Inferior, 

 ramus of the same. D. Gyrus descendens. T 4 . Gyrus occipitotemporalis lateralis 

 (lobulus fusiformis). T 5 . Gyrus occipitotemporalis medialis (lobulus lingualis). 



Secondary fissures of more or less importance are present in the 

 different lobes, subdividing the surface into convolutions: e. g. t in the 

 frontal lobe are found the pre-central, the superior and middle frontal 

 fissures; in the temporo-sphenoidal lobe the superior and inferior 

 or the first and second temporo-sphenoidal fissures; in the occipital 

 lobe, the transverse and inferior longitudinal fissures. 



Convolutions. The convolutions or gyres are the portions of 

 the cerebral surface comprised between the fissures. The arrange- 



