osteometry; the measurement of the bones 101 



This index is of rather questionable value, and gives little more than an 

 indication of the degree of development of the interosseous crest, which 

 can be noted almost as well by the eye. Where the crest is large the 

 transverse diameter is considerably in excess of the sagittal, and the shape 

 of the cross section at this place is somewhat triangular; where there is 

 little or no crest, on the other hand, the diameters are nearly equal, and 

 the cross section approximates a circle. In the first case the index is 

 a low number (72-75) ; in the second it is higher, reaching in the Simian 

 apes to above 80. Here also the figures for Homo neandertalensis are 

 unexpected, and resemble those of recent men, evidently because of 

 their high crests. As in the case of the ulna the study of cross section 

 outlines, both at this place and at others, is of more value than this 

 index. Such outlines are prepared by the method described by the 

 use of girdles of wax (cf. ulna). If these bands be filled with plaster 

 of Paris little disc-shaped pieces are obtained, which represent actual 

 cross sections which are very convenient for comparison. 



III. STUDY OF THE VOLAR PROJECTION 



Several striking differences in general form are brought out by com- 

 paring several radii placed in the volar plane, or, what is the same thing, 

 by comparing a series of volar projections (Fig. 36). The two most 

 important points are the collo-diaphyseal angle and the amount of curva- 

 ture of the shaft as a whole. 



9. Collo-diaphyseal angle.- — This is obtained in the projection by 

 marking upon it the axes of the two parts in question; (1) of the head and 

 neck, by a line connecting the center of the head, through the middle of 

 the shaft as far as the tuberosity, and (2) of the next ensuing portion 

 of the shaft. The angle thus formed may then be measured by means of 

 the transparent protractor. If one is dealing with an actual bone 

 instead of a projection, the bone must first be properly oriented, and 

 then the two axes marked by means of fine knitting-needles, attached 

 to the bone surface by wax or plastilena. The angle is then read as 

 before. 



Where there is no bend between the two parts considered, the head- 

 neck axis, and that of the ensuing portion form a continuous straight 

 line, and the angle = 180° (Fig. 36, I). This has been found in South 

 Germans, although the average is 171.6°. A slight bending reduces the 

 angle, which thus becomes less the greater the amount of bending ex- 

 hibited. The average angle for Australians is 165.4, and of Fuegians, 

 160.4, showing a progressively greater amount of bending in these races 

 as compared with Europeans. The Neandertal race, at 166°, shows an 

 amount of bending comparable with that of the lower modern peoples, 

 and the bending in the higher apes varies from 165° to 159°. 



10. Curvature index. — The amount of curvature of the whole shaft 

 may be expressed, in a way, similar to that used for the ulna, by fixing a 



UBT?ARY 

 UNIVERSITY OF CA T ^ORNIA 



