On the Influence of Muscular Attachments. 63 



section of the femoral shaft to a lower level than usual. 

 In the femora under consideration a comparatively short 

 popliteal surface was associated with exceptional attach- 

 ments of the muscles, and yet none of the popliteal 

 diameters were out of the ordinary. 



I am therefore forced to conclude that convexity of the 

 popliteal surface, and high popliteal indices, are not to be 

 explained by an increase of the antero-posterior diameter 

 caused by muscular attachments. In searching for a 

 sufficient explanation of high popliteal indices, it is well 

 to bear in mind that all varieties of platymeric, pilastric, 

 and popliteal indices are compatible with the erect attitude, 

 since they are all found in man ; and, therefore, when 

 muscular attachments will not account for the proportions 

 of the femoral shaft, it is probable that they are merely 

 mechanical adaptations for the resistance of strain in 

 certain directions. The ordinary type of popliteal surface 

 in European femora is one which is flat, or it may be 

 slightly concave between the outer and inner supracondyloid 

 ridges, and yet among rachitic specimens (8) a decided 

 convexity of this surface may be present. Under normal 

 healthy conditions some similar mechanical adaptation 

 might be expected in the femora of those races which were 

 characterised by the peculiar race attitude of " sitting on 

 their heels," and in this connection it is interesting to note 

 that I have found the highest average of popliteal indices 

 among the femora of aboriginal Australians, Hindoos, 

 Kaffirs, and Bengalees. 



At the same time we must not lose sight of the fact that 

 it is permissible to regard a highly convex popliteal surface 

 in the light of a historical reversion to the mechanical pro- 

 portions which characterise the femora of the gibbon. In 

 this anthropoid ape the upper part of the lower third of 

 the shaft of the femur undoubtedly presents cylindrical 

 proportions, which, however, disappear in the proximity of 

 the knee-joint. If we accept the hypothesis of Dr Dubois 

 that a gibbon-like ape was the direct progenitor of homo 

 sapiens, then the Trinil femur might very readily be that 

 of Pithecanthropus erectus and femora with great convexity 



