Nervous and mental diseases . emispheres, consequently we can not expect a close resem-blance between the brains of different individuals. There are alsovariations for sex, age, and body-weight. Very often there are super-numerary or unusual convolutions on one or both s;^°«, A number ofmethods have been devised by Reid, Horsley, Hare, and others, to mapout on the scalp the underlying cortical areas. They all have valuable 168 DISEASES OF THE BRAIN PROPER. features; but if you apply a number of them to the same head, so im-portant a landmark as the Sylvian fissure will be variously
Nervous and mental diseases . emispheres, consequently we can not expect a close resem-blance between the brains of different individuals. There are alsovariations for sex, age, and body-weight. Very often there are super-numerary or unusual convolutions on one or both s;^°«, A number ofmethods have been devised by Reid, Horsley, Hare, and others, to mapout on the scalp the underlying cortical areas. They all have valuable 168 DISEASES OF THE BRAIN PROPER. features; but if you apply a number of them to the same head, so im-portant a landmark as the Sylvian fissure will be variously exactness, for the reasons already indicated, is not within therange of possibility. With the formulas named, the difficulty lies largelyin selecting rather indefinite anatomical points, like the parietal boss orthe temporal ridge, and making measurements in inches or other unitsfrom these points on ill-defined lines or angles. A simpler and proba-bly more accurate plan is advocated by Drs. Anderson and Makins, of Msp. Fig. 70.—Craniocerebral guiding lines traced upon a cast of Professor Cunninghams (from a photo-graph). GP, Glabellar point, glabella opposite superior border of orbit; IP, inial point, at externaloccipital protuberance; MSP, mid-sagittal point, midway between GP and IP; , angular point,external angular process opposite upper border of orbit; , squamosal point, intersection of obliqueand frontal lines at junction of middle and lower thirds of latter; PP, parietal point, termination ofoblique line, equidistant with FS2 from squamosal point; , pre-auricular point, depression infront of tragus, at the level of upper border of external auditory meatus; FS1, commencement offissure of Sylvius, five-twelfths of distance from to ; FS2, bifurcation of fissure of Sylvius,seven-twelfths of distance from to ; FS3, termination of fissure of Sylvius, >2 0I an incaabove PP, in a direction parallel to frontal line; FR1, upper extrem
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