THE FEMUR. 359 



seen in sections parallel with the lower wall of the neck (Fig. 375) ; it appears also 

 in transverse ones. When strongly developed it can be shown as a real septum by 

 gouging away the spongy tissue of the posterior intertrochanteric ridge beneath 

 which it passes. 



Sexual and Individual Variations.— Apart from general lightness of struc- 

 ture, the female femur presents distinctly smaller articulations than the male. The 

 average diameter of the head of thirty-eight male bones is 4.8 centimetres, and of 

 twenty-six female ones 4.15 centimetres. In only two of the male bones is the 

 diameter less than 4.5 centimetres, and in only two of the female is it greater. Both 

 of the latter are long ones. In women the size of the head increases with the length, 

 but in men a short femur is about as likely to have a large head as a long one. The 

 breadth of the articular surface of the knee is less conclusive ; the averages are 8.3 

 centimetres and 7.4 centimetres, but there is much overlapping. The peculiarity 

 of outline in the typical female femur is very characteristic when well marked : the 

 shaft narrows gradually from the condyles till at or above the middle the nar- 

 rowest part is reached, above which there is a much less evident expansion. The 

 typical male bone narrows much more suddenly above the condyles, so that the 

 stouter shaft soon reaches a tolerably uniform thickness. The iyicliyiation of the 

 shaft is somewhat greater in woman. The angle with a vertical line in the above 

 series is 9.3° in man and 10.6° in woman. (According to Bertaux, it is 8.75° 

 and ii°.) It is naturally greater in shorter femurs, and consequently is of very 

 doubtful value as a sexual characteristic, especially in view of the great individual 

 variation. The angle of the 7ieck with the shaft is of minor significance. In the 

 writer's series it ranges from 110° to 144°, the average for men being 125.1° and 

 that for women 125.6°. In the male bones there is little connection between the 

 length of the femur and the size of the angle ; in women long bones have a large 

 angle and short bones a small one. The average angle of the longer half of the 

 male bones is 126.5° and that of the shorter 123.6°, while the longer and shorter 

 halves of the female series give 129.2° and 121.9° respectively. A long neck gen- 

 erally has a high angle and a short neck a low one.^ Thus it appears that there are 

 great variations in the angle of the shaft and that of the neck. The same is true of 

 almost every detail. The forward iyiclination of the neck is in two-thirds of the cases 

 from 5° to 20°, and usually from 12° to 14°. Its extreme is 37°. Very rarely this 

 angle is negative, — that is, the neck slants backward. An extreme negative angle 

 of 25° has been observed, but this is extraordinary.^ The curve and outline of the 

 shaft vary much. An extreme form is the pilastered femur, very convex, with a 

 prominent linea aspera, generally stout, implying strength. An opposite form is 

 nearly straight, has a low linea aspera, and is flattened before and behind in the 

 upper part of the shaft. In extreme forms the depression in the front of the top of 

 the shaft is increased and bounded internally by a sharp ridge running up to the 

 under side of the neck, which usually has a low angle. Though apparently weaker, 

 this form is sometimes found in very powerful men. 



The index of the shaft is the proportion of the thickness to the breadth, the 



latter being 100. Thus ( ''"'treadth '°° )'- ^his is taken at about the middle of the 

 shaft where the linea aspera is most prominent. It is said to be greater on the right 

 than on the left and in men than in women. Bertaux found the average in adults 

 104.4, and in a series of young femurs 112. i. 



The index of the neck is the proportion of the thickness to the height. Thus 

 ^thickj^s_>ooo^ The average is 133.05. It is a trifle higher in women, but the 



difference in unimportant. 



A strong convexity of the shaft outward as well as forward suggests a patho- 

 logical condition. 



Development and Changes. — The shaft begins to ossify not later than the 

 seventh week of foetal life. A centre appears in the lower end during the last month 

 of pregnancy. It is rarely wanting at birth, but the precise time of its appearance 

 as well as its size are too variable to make it a very valuable guide to the age of the 



^ H. H. Hirsch : Anatomische Hefte, Bd. xx.xvii., 1S99. 

 2 Mikulicz : Arch, fiir Anat. and Phys., 1878. 



