SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 



35 



siderably in man was long since shown by Hrdlicka.' The present studies 

 demonstrate that it ditTers also in animals. In general it is represented by the 

 same geometrical types as in man, being triangular, elliptical, round, quad- 

 rangular, and plano-convex. Also, as in man, besides the femora which are 

 fairly true to a type, there are others which are irregular or indeterminate in 

 shape and do not admit of any definite classification. 



Generally speaking, liowever, tliere was one particular shape which was 

 more prominent than any other, and that was the elliptical. This was found 

 to be true of the majority of adults among amphibians, reptiles, birds, bats, and 

 other mammals, and, therefore, was the most common shape of femur below man 

 as far as these examinations were concerned. The differences in the leng-ths 

 of the two main diameters were usually small, the lateral diameter being gen- 

 erally the longest; in only a few specimens — as in the femur of the seal — were 

 the lateral diameters greatly in excess of tlie aiitero-posterior. The femora of 

 the Hyla cinerea, Erinaceus europeus, Tatu novemcinctus, Castor canadensis, 

 and Rhinoceros hicornis had very long posterior, lateral, curved or straight 

 ridges and differed very materially from other femora. The variations from 

 the circular and elliptical shapes were in a measure dependent upon the develop- 

 ment of tlie Ihiea aspera. In some femora this was absent; in others it was 

 fairly well developed; and in still otlnu-s its development was extreme. In the 

 table which follows will be found the various shapes of the femora of the lower 

 animals expressed in percentages: 



SHAPE OF THE SHAFT OP THE LOWER ANIMAL FEMUR AT THE MIDDLE 



No. of 



femora 



examined 



Triangular 

 Per cent 



Amphibians 



Reptiles 



Birds 



Bats 



Other Mammals. 



39 

 34 

 40 

 55 

 133 



Totals. 



301 



26 

 29 

 12 

 

 21 



17 



II \ III 

 Elliptical I Round 

 Per cent Per cent 



41 

 53 

 52 

 72 

 53 



28 

 9 

 18 

 25 

 15 



50 



25 



IV 



Quad- 

 rangular 



Per cent 



V 

 Indeter- 

 minate 



VI 

 Piano- 

 Convex 



Per cent Per cent 





 

 15 

 3 

 6 



0.7 



Rel.\tion of Steuctuee to Sh.\pe 



As far as present investigations are coueerned, no special relation of the 

 histologic structure of the femur to the shape of its shaft has been determined. 

 The prolonged posterior ridge of the triangular sections is due to the linea 

 aspera, and wherever the latter is well developed macroscopically it is com- 

 posed of Haversian systems regardless of the type of the rest of the bone. 



As will be seen later, the linea aspera seems to have a development quite 

 distinct from the rest of the femur. 



' See in this connection, Hrdlicka, A. — Typical forms of shaft of long bones. Proc. Amer. Assoc. 

 Anatomists, 14th Sess., 1900 (Washington, 1901). pp. 55-69. 



