OSTEOMETRY; THE MEASUREMENT OF THE BONES 103 



which marks the point a, on the margin (Fig. 36). The point 6 is the 

 deepest point of reentrance of the distal curve seen on this outline, as 

 shown also in Fig. 36. Now, connect by a line points a and b and we 

 have the tangent sought. Finally, upon this as a base erect the longest 

 possible perpendicular to the outer line of the margin, and the proportion 

 of this to the entire tangent ab will indicate the amount of curvature; 

 , height of greatest perpen. X 100 



length of tangent chord ab 



This index is always a small one, varying from 2 in modern culture 

 races to over 6 in the strongly curved radii of the Neandertal species. 

 Where the curve is large, it indicates a broad interosseous space, which 

 in turn suggests a large suiface for the origin of the finger flexors, and an 

 ability to cling very tenaciously to such an object as a tree limb. In 

 this connection the large amount of curve in the Neandertals is significant. 



TABLE OF SHAFT CURVATURE INDICES, AVERAGES 



Higher apes 



Gorilla 5.7 



Orang-utan 5.1 



Chimpanzee 4.3 



Gibbon 3.6 



Homo neandertalensis 



Neandertal specimen 5.2 



Spy 1 6.5 (approx.) 



Spy II 5.2 (approx.) 



Homo sapiens 



South Germans 3.2 



Melanesians 3.0 



Burmese 2.7 



Fuegians 2.5 



IV. STUDY OF THE SAGITTAL PROJECTION 



In turning the bone around to a position 90 from the volar plane, 

 it comes into the sagittal plane. Here but one important character 

 has thus far been observed, and that is, a second collo-diaphysial angle, 

 which marks the amount of backward projection of the proximal end of 

 the bone. This can be measured by the same methods as are used for 

 the collo-diaphysial angle of the volar plane (No. 9), and has been found 

 to average 172.5 in the people of Oceanica and 175.0 among the South 

 Germans, in both cases a greater bend than in the volar diaphysial angle. 

 This angle may prove to be important, but thus far it has not been used 

 very much, and need not be listed. 



V. THE TORSION OF THE SHAFT 



If in number of radii the maximum length line of the distal articular 

 surface be plainly marked, that is, the line used above in determining 

 the volar plane, and the bones be then placed in a parallel row upon a 



