ME. BUSK ON YEDDAH SKULLS. 



169 



2. Breadth, taken wherever it is found to be placed, sometimes 

 higher, sometimes lower. (Fig. 2.) 



3. Height t measured from the level of the foramen magnum to 

 the highest part of the vertex. 



4. The least frontal breadth, measured usually immediately be- 

 hind the external orbital process (I f fig. 3) . 



5. The greatest frontal breadth, measured at the point where it 

 exists, which corresponds most usually with that where the tem- 

 poral line crosses the coronal suture (gf fig. 3). 



6. The parietal breadth, measured between the centres of the 

 parietal bones (p, fig. 3). 



7. The occipital breadth, taken between the external angles of 

 that bone (fig. 3). 



These last four measurements represent, however, only the chords, 

 as it were, of the respective arcs above them ; the arcs themselves 

 are roughly estimated by the distance over each arc from the 

 middle of one external auditory opening to that of the other ; and 

 these measures mav be termed, 



8. The frontal transverse arc. 9. The vertical transverse arc. 

 10. The parietal „ ,, 11. The occipital „ „ 

 The directions in which they are taken, by means of a graduated 



tape, are shown in the dotted lines f v,p, o, in fig. 1. But in 

 order to render the measurements of the three regions still more 

 complete, it is necessary to ascertain, 1st, the length in an antero- 

 posterior direction of each region, and, 2nd, the perpendicular 

 depth, as it were, of the three cerebral lobes. The latter object is 

 attempted by measuring the distance between a point correspond- 

 ing with the pons Varolii to the surface of the skull in a straight or 

 radial direction ; and these measures are thus taken : — If a thin 

 wire be passed straight through the middle of the auditory open- 

 ing, and made to perforate the inner wall of the tympanum, it will 

 enter the cavity of the cranium by the internal auditory opening, 

 and of course pass out on the opposite side in the same way. In 

 doing this, it would pass pretty nearly through the centre of the 

 pons Varolii. Now, if an instrument be so constructed as to have a 

 conical plug capable of being introduced into each of the external 

 auditory openings, and fitted to move up and down on the branches 

 of an instrument constructed upon the plan of a shoemakers gauge, 

 the distance from the central point in question . = the centre of the 

 pons will be measured, including the thickness of the cranium, by 

 the distance of the centres of the plugs from the stem of the in- 

 strument, when that is made to touch any part of the periphery 



LINN. PEOC. — ZOOLOGY, VOL. YI. 12 



