820 



I UROLOGY 





(Figs. 725, 726) is situated about the middle of the lateral surface of the hemisphere?, 

 and begins in or near the longitudinal cerebral fissure, a little behind its mid-point. 

 It runs sinuously downward and forward, and ends a little above the posterior 

 ramus of the lateral fissure, and about 2.5 cm. behind the anterior ascending ramus 

 of the same fissure. It described two chief curves: a superior genii with its con- 

 cavity directed forward, and an inferior genu with its concavity directed backward. 

 The central sulcus forms an angle opening forward of about 70 with the median 

 plane. 



The Parietooccipital Fissure (fissura parietooccipitalis') . Only a small part of this 

 fissure is seen on the lateral surface of the hemisphere, its chief part being on the 

 medial surface. 



The lateral part of the parietooccipital fissure (Fig. 726) is situated about 5 cm. 

 in front of the occipital pole of the hemisphere, and measures about 1.25 cm. in 

 length. 



FIG. 727. Medial surface of left cerebral hemisphere. 



The medial part of the parietooccipital fissure (Fig. 727) runs downward and for- 

 ward as a deep cleft on the medial surface of the hemisphere, and joins the calcarine 

 fissure below and behind the posterior end of the corpus callosum. In most cases 

 it contains a submerged gyrus. 



The Calcarine Fissure (fissura calcarina) (Fig. 727) is on the medial surface of 

 the hemisphere. It begins near the occipital pole in two converging rami, and runs 

 forward to a point a little below the splenium of the corpus callosum, where it is 

 joined at an acute angle by the medial part of the parietooccipital fissure. The 

 anterior part of this fissure gives rise to the prominence of the calcar avis in the 

 posterior cornu of the lateral ventricle. 



The Cingulate Sulcus (sulcus cinguli; callosomarginal fissure) (Fig. 727) is on the 

 medial surface of the hemisphere; it begins below the anterior end of the corpus 

 callosum and runs upward and forw r ard nearly parallel to the rostrum of this body 

 and, curving in front of the genu, is continued backward above the corpus callosum, 

 and finally ascends to the supero-medial border of the hemisphere a short distance 

 behind the upper end of the central sulcus. It separates the superior frontal from 

 the cingulate gyrus. 



The Collateral Fissure (fissura collateralis] (Fig. 727) is on the tentorial surface 

 of the hemisphere and extends from near the occipital pole to within a short dis- 

 tance of the temporal pole. Behind, it lies below and lateral to the calcarine fissure, 



