CEO-MAGNON SKULLS AND BONES. 



105 



Fig. 45. 



Diagrams showing the Trans- 

 verse Section of an Ordinary 

 (No. i) and of a Platycnemic 

 (No. 2) Tibia. 



A 



Fig. 45, No. i, represents the section of a triangular tibia. The three angles, A El, correspond to the 



three edges, anterior, external, and internal. The side A E corresponds to the outer face, on which the 



tibialis anticus has its insertion ; A I is the inner face, subcutaneous ; E I, 



lastly, is the posterior face, in which the situation of the nutritive foramen 



is indicated by N ; the inner portion of this face (I N) corresponds to the 



surface of insertion of the popliteus, and its outer part (N E) to the surface 



for the tibialis posticus. 



In fig. 45, No. z, representing the section of a flat tibia, with the same 

 letters indicating similar parts, we see that the posterior face has an 

 entirely different shape ; for its outer portion (E N) forms part of the 

 outer face, and its inner portion (N I) forms part of the inner face, so 

 that the only part of this posterior face which has really a backward 

 aspect forms merely a thick edge, in which the nutritive foramen opens 

 at N. Such a flattened shaft has therefore only two faces and two 

 edges: 1st, an anterior edge, A, or "crest of the tibia," like that of the 

 triangular tibias, but rather more trenchant; 2nd, a posterior edge, N, 

 which is formed above by the upper part of the " popliteal line " (fig. 44, 

 pp'), and lower down by the " tibial line" (fig. 44, _;'/); 3rd, an inner face, formed in front by the inner 

 face of the ordinary tibias, behind by the surface for the popliteus ; 4th, an 

 outer face, formed in front by the outer face of the ordinary tibias, and 

 behind by the surface for the tibialis posticus. Having thus illustrated 

 the anatomical correspondence of parts in the tibias of the two types in 

 question, we can more easily describe the conformation of the flattened 

 tibias. 



Their outer face (fig. 46) has in its lower portion the breadth of ordi- 

 nary tibias ; but in its upper moiety it widens considerably ; and through 

 this widened portion a vertical salient line (B C) passes from above down- 

 wards, exactly parallel to the crest of the tibia (A A), and lower down, 

 about where the shaft begins to be triangular, it is continuous with the 

 outer edge (C D), which gives insertion, as before said, to the interosseous 

 aponeurosis ; and this also is partly attached to the line above described, 

 whence it results that the portion of the bone in front of the " interosseous " 

 line gives insertion to the tibialis anticus and corresponds to the outer face 

 of the triangular tibias ; whilst the portion behind it (C Bpp'jj') gives 

 insertion to the tibialis posticus, and consequently corresponds to the outer 

 part of the posterior face of the triangular tibias. 



Likewise in examining the inner face of the sharp-shin tibias we find 

 that throughout the compressed portion this inner face is widened. In 

 the lower portion, where the shaft is triangular, we distinctly recognize 

 the inner edge, which is not less evident than in ordinary tibias ; but, in 

 following this edge from below upwards, we see on coming to the level of 

 the flattened portion that it disappears entirely ; in continuance with it 

 some slight rugosities just indicate a longitudinal line, which traverses the 

 inner face of the flattened and widened portion, just as the " interosseous " 



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