Feb. 4, 1886] 



NA TURE 



315 



the middle line on the crown of the head, so that it lies as 

 nearly as possible on the shortest line between the nasion 

 and the protuberantia occipitalis, tt is of no consequence 

 whether the knot of the thread lies a little forward or 

 backward. Two arms of the thread are placed anteriorly 

 and posteriorly, one over the nasion, the other over the 

 occiput. The other two are placed transversely across 

 the skull, so that they correspond to the anterior border of 

 each auditory meatus. 



The next thing is to fix the points at which the cross- 

 threads cut the line of the ground-plane. For this pur- 

 pose an elastic band is placed around the skull so that it 

 lies on the anatomical points indicating the anterior and 

 posterior ends of the long axis, and in a straight curve 

 round the skull between these points. When the skull is 

 placed with this line horizontal, we obtain the ground or 

 horizontal plane from which the other curves are to be 

 taken. For the purpose of recording the curves millimetre 

 paper is used, and the principal axes of the skull marked off 

 on it. The long or median axis is measured with cali- 

 pers. The total length is divided by two, and each half 

 is measured off in a straight line on the millimetre 

 paper from a centre. By a similar process the 

 transverse axis of the skull is obtained at the points 

 where the transverse threads cut the horizontal plane. 

 A rectangular figure is then drawn through each 

 of these points, indicating the length and breadth 

 of the cranium. This forms a boundary-line for the 

 tracing. In order to determine at what point the 

 transverse axis intersects the longitudinal axis in the 

 skull, it is necessary to find out how far behind the mid- 

 point of the long axis the transverse axis is situated. This 

 is done by measuring the distance from the anterior point 

 on the skull to the point where the transverse and hori- 

 zontal planes intersect at the anterior border of each 

 auditory meatus (which we shall call the " ear-point "), 

 and then marking it off on the millimetre paper, taking 

 as a starting-point the anterior end of the long axis. 

 The true zero or middle point of the skull will be that at 

 which the transverse axis intersects the long axis. This 

 middle point may bear different relations to the middle 

 point of the long axis in that it may coincide with it or be 

 behind it. Whatever may be its relations to the long 

 axis, the transverse axis must be placed on the paper, so 

 that it crosses the centre of the rectangular figure. If 

 the middle point is behind the centre of the long axis, 

 the anterior end of that line will project a corresponding 

 distance beyond the anterior boundary of the figure, 

 while its posterior end will fall at a corresponding dis- 

 tance within it. This will show the projection of the 

 skull forwards and backwards in relation to the ante- 

 rior borders of the auditory meatus. Should the base of 

 the skull or the ground plane not be symmetrical, the 

 axis of length and that of breadth will not be at right 

 angles to each other, but more or less oblique. Having 

 fixed the position of the axes with respect to the rect- 

 angular figure, the horizontal curve is drawn on the paper 

 in four segments in the following way : — A flexible, but 

 absolutely inelastic piece of lead wire is laid on the skull, 

 with its one end corresponding to the right ear-point ; it 

 is moulded to the skull, along the horizontal line, to the 

 anterior point in front, then from the left ear-point to the 



anterior point, and finally from each ear-point to the 

 posterior point. The segments are then carefully placed 

 on the paper with the points all coinciding to those on 

 the marked quadrilateral, and, with a pencil, a tracing on 

 the paper is made along the inner side of the lead wire. 

 In this way the outlines of several skulls can be super- 

 imposed ; the transverse and longitudinal axes of all the 

 skulls must, however, be made to coincide. 



The median longitudinal curve is taken from the end 

 points of the long axis in two pieces, as it is not possible 

 to take it all at once, and the knot on the cross-threads 

 is utilised for determining a point on the curve from 

 which each segment can be taken. Its position is defined 

 on the paper in the following manner : — With a pair of 

 compasses the distance from the anterior end point to 

 the knot is measured on the skull and then laidotT on the 

 paper backwards, starting at the anterior end of the long 

 axis line. The distance from each side point to the knot is 

 measured and laid off on the paper so that the two lines 

 converge and meet in front. The distance of the point of 

 union to the zero will represent the sagittal height of the 

 skull. From the anterior end of the long axis a segment 

 having a radius equal to the distance from the side point to 

 the knot is marked off with the compasses on the paper, 

 and another segment is likewise marked off from the zero 

 point with a radius equal to the distance between the zero 

 point and that at which the two side lines meet. Where 

 the two segments intersect, we have a fixed point 

 which will represent the position of the knot. The 

 accuracy of the point so determined may be further veri- 

 fied by a similar process from the posterior end of the 

 axis line. The lead wire is then laid along the curve, 

 first the one half and then the other, and on being placed 

 on paper is traced with a pencil. 



Curves of the transverse diameters of the calvaria are 

 taken in a similar manner. 



The method is one which requires a considerable 

 amount of care and time. It has the advantage of not 

 requiring any complicated apparatus, but whether its 

 results are equally reliable and compensate for the time 

 required in the manipulation is possibly an open ques- 

 tion. For laboratory work we are inclined to think that 

 the stereograph of Broca will prove much more useful, 

 and repay its cost in the rapidity and accuracy with 

 which all the tracings described in Dr. Rieger's mono- 

 graph can be made. Moreover, with the stereograph, 

 drawings of the face can be made which are not practicable 

 with the graphic method of Rieger. 



The plane of orientation proposed by Rieger cannot be 

 considered quite satisfactory, owing to the difficulty of 

 determining accurately its posterior end. A plane of 

 orientation of a purely anatomical character, which we 

 have frequently used, is that with the basio-nasial line 

 horizontal, it being the axis on which both the brain- 

 case proper and the facial portion of the skull are de- 

 veloped. These anatomical planes have the disadvantage 

 of placing the skull in an unnatural position, but are of 

 the greatest use in comparing outlines of the side view 

 of different skulls. For general purposes, however, we 

 have found the alveolo-condylar plane of orientation to 

 be the most useful. 



J. G. Garson 



