APPLIED ANATOMY. 



The angular gyms surrounds the posterior end of the first temporal sulcus 

 (parallel fissure) and is, therefore, 3 or 4 cm. (i^ to \y z in.) posterior to the 

 parietal eminence. 



The transverse occipital sulcus is a continuation of the interparietal sulcus 

 to just beyond the parieto-occipital fissure. 



The lateral occipital sulcus lies close to the tentorium; it divides the occipi- 

 tal lobe into superior and inferior convolutions. (Sometimes these two sulci divide 

 the lobe into three convolutions, superior, middle, and inferior.) 



The Fissures in Children. In childhood the fissure of Rolando is somewhat 

 more vertical than in adults; the fissure of Sylvius has its point of division, a little 

 higher and runs up to and usually above and in front of the parietal eminence 

 (Dana, Med. Record, Jan. 1889, p. 29). After the age of three years, the relative 

 position of the fissure to the parietal eminence begins to approach that of the adult. 

 (For variations due to age see Cunningham: ' ' Contributions to the Surface Anatomy 

 of the Cerebral Hemispheres," 1892.) 



The objects of cerebral topography are mainly to ascertain in case of injury or disease of 

 the superficial structures what parts of the brain beneath are liable to be involved, and for opera- 

 tive procedures, in order to expose the affected areas. 

 The convolutions and sulci are so variable that all 

 guides are only approximate. In order to overcome 

 this defect and provide for unusual conditions, the 

 openings in the skull are usually made quite large. 

 The flaps of scalp and bone may even embrace the 

 entire parietal bone or a quarter of one hemisphere. 

 As regards the various points the upper Rolandic 

 point is generally conceded to be 15 mm. (% to jhs in.) 

 posterior to the midpoint between the glabella and 

 inion. The angle which the fissure forms with the 

 median line varies from 64 to 75. Cunningham 

 gives it as 70 and Arthur W. Hare as 67. Chiene's 

 method of finding the desired angle is usually accepted 

 as reliable. He takes a square piece of paper and 

 folds it obliquely from corner to corner making 45, 

 and then folds it a second time making 22^. The 

 two being added together give 67^ as the angle made 

 by the fissure of Rolando with the anterior portion of 

 the longitudinal fissure. 



The pterion was placed by Broca at the coronal su- 

 ture. This is 15 mm. (fin. ) in front of theSylvian point. In several formalin hardened brains, we 

 found this latter to be at the posterior angle of the pterygoid wing, and in twenty measured 

 skulls the Sylvian point averaged 42 mm. 

 (i^i in.) behind the angular process. Reid 

 placed it at 50 mm. (2 in.) , which we think too 

 much. Anderson and Makin placed it at i ^ to 

 2 in. Thane and Godlee placed it 35 mm. back 

 and 12 mm. up, which is just a trifle farther 

 forward than we have located it. Landzert 

 and Heffler gave it as at the summit of union 

 of the great wing of the sphenoid with the 

 temporoparietal suture, as we have given it. 

 When prolonged, the Sylvian fissure some- 

 times crosses the median line 1.5 cm. (^ in. ) 

 above the parieto-occipital fissure, but more 

 usually we have found it to be close to the 

 fissure, which agrees with Reid. The parieto- 

 occipital fissure has been located by some 

 authors near the lambda, but we would place it 

 1.5 cm. (% in.) above. We believe the parie- 

 tal eminence to be a fairly reliable guide to the 

 posterior extremity of the fissure of Sylvius. 

 Method of Anderson and 'Makin for 



Locating the Fissures of the Brain. For the sake of comparison the following method of 

 Wm. Anderson and George Henry Makin (Jour. Anat. and Phys., vol. xxiii, 1888-89, p. 455) is 



FIG. 51. Chiene's method of folding a square 

 piece of paper in order to obtain an angle of 67^ 

 degrees. 



FIG. 52. Method of Anderson and Makin for locating the 

 fissures of the brain. 



