Operative surgery . ontal and parietal lobes, about three and a halfinches, forming an angle of sixty-seven degrees with the median line of thecranium (Figs. 388 and 389). It is located by either of the following topo-graphical plans (Figs. 385, 386, 287, and 388) or by mechanical means () devised for the purpose. Horsleys -fissure meter is calculated to fulfillthe requirements of each class of cases. Horsley, finding that the anglebetween the central and longitudinal fissures varied somewhat with the shapeof the head, as modified by the cephalic index, devised an instrument providedwit
Operative surgery . ontal and parietal lobes, about three and a halfinches, forming an angle of sixty-seven degrees with the median line of thecranium (Figs. 388 and 389). It is located by either of the following topo-graphical plans (Figs. 385, 386, 287, and 388) or by mechanical means () devised for the purpose. Horsleys -fissure meter is calculated to fulfillthe requirements of each class of cases. Horsley, finding that the anglebetween the central and longitudinal fissures varied somewhat with the shapeof the head, as modified by the cephalic index, devised an instrument providedwith a rotating arm corresponding to the central fissure, which can be variedto meet the deviations of the various cranial indices. The degree of the cranialindex is determined by dividing the transverse diameter of the head by theantero-posterior diameter. According to Horsley, in a head with a cranialindex of the central fissure runs at an angle of 69°, the angle increasing OPERATIONS ON THE NERVOUS SYSTEM. 247. Fig. 284.—Horslevs fissuremeter. or diminishing one degree for every two degrees increase or decrease in thecranial index. The instrument is so applied to the head (Fig. 28-4) that themovable arm at its center of rotation will correspond to the upper end ofthe central fissure. The arm can be rotated to conform to the cranial indexas established by measurements already method of determining the positionof the fissure is ingenious, available, and ef-fective (Fig. 285). He folds a square piece ofpaper once, so as to form a triangle ABC,the corners B and D coinciding. The angleB A C is one of 45°. The dotted edge D A isfolded back so that the dotted edge D A isapplied to the dotted line C A. Each of theangles DAE and E A C is evidently half of45°—that is, °. Leaving the flap DAEfolded, the paper is unfolded at the line C A,forming the figure A B C E. The angle BA E being made up of one of 45° and one °, is evidently °, which is,
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