MEMOIRS OF T11E NATIONAL ACADEMY OF SCIENCES. 167 



guidance has been the contour of the processus auditorius or tympanic bone. Where this was 

 complete in its upper portion, as it rarely is in man even in the lower races, we had no trouble in 

 establishing our point. Where a good vestige of the upper part remained, not too far out of 

 place, we were contented to take such vestige for our guide ; but where a large segment of the 

 bone was completely missing we joined the upper horns of the remaining portion by means of a 

 pencil mark described as directly as possible from one horn to the other on the roof of the meatus 

 and took the highest point of this arched line for our landmark. In leveling the skull for the 

 German horizontal plane and in taking the auricular heights we felt less hesitancy in depending 

 on this guiding point than in taking vertical arcs. Here it was most doubtful. 



Table i is intended not only to answer the purposes of the present investigation, but possibly to 

 serve as a model for future catalogues which may be issued by the Surgeon-General's Office. It has 

 been designed with a view of economizing space and making reference easy. The peculiarities of 

 its plan require little explanation. On the first page of the table and on its duplicate fly-leaf we 

 have given a condensed description or indication of each measurement, index, or other item suffi- 

 cient, we believe, for ready reference. In order to get each description within the space of one line 

 we have rarely used the exact words of the original authors. For the measurement of the German 

 anthropologists we have been especially compelled to reject the circumlocutions of the Frankfort 

 agreement in describing guiding marks and have adopted instead the specific terminology of 

 crauiometric science. "Frankfort," in the table, denotes that the preceding rule is to be found, 

 in substance, in the Frankfort agreement.* "Topinard" denotes that it is to be found in the 

 work of this author already referred to. The number or letter which follows either of these names 

 corresponds with that given to the item by the quoted authority; thus "Frankfort 1" refers to 

 the first measurement of the Frankfort agreement. Feeling that our brief references to rules 

 might often be insufficient for those who had not at hand copies of the oft-quoted Frankfort agree- 

 ment and of the rules of Topinard, we have supplied these in Appendices A and B of this work. 



$ 3. THE PICTURES OF THE SKULLS. 



The outline tracings of the skulls shown in plates 1 to 54, inclusive, are reductions to half 

 size, made by means of a pantograph from orthogonal or geometric drawings. 



It seems proper that we should here describe the apparatus and the method in use for the 

 past five years in the Army Medical Museum,* by which these orthogonal tracings were made, 

 since both seem to differ in many respects from those in use elsewhere, as far as we may judge 

 from published descriptions. 



Fig. 23 represents the complete apparatus in use. It consists of a frame (a, a, a), inside of 

 which is an open box (b) nearly filled with dry sharp sand (so arranged that it may be raised and 

 lowered by means of a lever (c), a movable and adjustable mounted pin (d), an ordinary car- 

 penter's or draughtsman's square, and a tracer of peculiar construction, which has been named the 

 periglyph (e). The frame is surmounted by a movable plate of glass, thinly varnished on both 

 sides to receive the tracing. 



The periglyph is shown reduced in Fig. 24. It consists of a standard (a), a base (b) (both 

 made preferably of vulcanite or hard wood), supported by two padded points (c), and by the sharp 

 steel style (d), which makes the tracing; vertically above the extreme point of the style is a pin 

 hole on an adjustable arm (e). 



In other laboratories they use diopters, somewhat similar to this instrument in appearance, 

 with which the outline is drawn by means of a pen or pencil held in hand. It needs but a single 

 trial to convince one that our instrument, with its fixed steel tracer, is vastly more reliable and 

 convenient. Of course the steel point would not trace on plain glass as the pen does; the thin 

 coat of varnish renders the use of the style practicable. 



* Verstiindigung iiber ein gemeinsames crauioinetrisches Verfahren ; Archiv fur Authropologie, Bd. xv, Braun- 

 schweig, 1884, pp. 1-8. (S<;c Appendix B.) 



t \V. MATTHEWS: Apparatus for tracing orthogonal projections of the skull, in the United States Army Medical 

 Museum. Journal of Anatomy and Physiology, vol. XXI, London, lSSli-'S7. pp.42-ir>. 



