698 MAMMALIAN ANATOMY 



some specimens it is abnormally large and hooked. Inasmuch as 

 the distance from the head to the edge of the greater trochanter is 

 variable, the digital fossa varies in width ; it also varies in depth and 

 in the extent to which it is overhung by the edge of the trochanter. 

 The articular surface on the head is sometimes separated from the 

 digital fossa by a well-marked tubercle. The pit on the head for the 

 ligamentum teres is occasionally obscure ; it is usually marked by 

 two parallel deeper cuts. 



The greater trochanter varies in antero-posterior width and in the 

 clearness of the markings on its outer surface. A foramen is often 

 present between the head and the lesser trochanter, above the anterior 

 intertrochanteric line. 



The shaft appears to be constantly straight, and exhibits only slight 

 variations in its curvature. In one specimen the superior end of the 

 internal border, below the anterior intertrochanteric line, presented a 

 well-marked swelling for the tipper end of the vastus internus. 



The linea aspera varies in development. In one specimen ex- 

 amined it was very high, especially the inner branch limiting the 

 vastus internus muscle. In another specimen the lower part of the 

 outer branch and all of the common trunk was drawn inward and 

 backward into an irregular sheet six millimetres wide and twenty- 

 eight millimetres long, to which was fastened the adductor muscle. 



The external border may be indistinct throughout ; its upper part 

 is not infrequently developed into a decided crest. The anterior surface 

 of the trochlea varies in width and in degree of concavity. In some 

 specimens its inner border is shorter and more arcuate, in others both 

 borders appear to be equal. The width, depth, and degree of obliquity 

 of the intercondyloid notch are subject to slight variations. 



HUMAN FEMUR. 



The femur in man (Fig. 535) is the longest and strongest bone in 

 the skeleton. In the cat it ranks in length below the tibia and the 

 ulna. The shaft of the human bone is also relatively more slender 

 than in the cat ; it is cylindrical, and bowed more strongly forward. 



The head forms about five-tenths of a sphere, and is separated 

 from the rest of the upper extremity by a longer and more clearly 

 defined neck, on the posterior part whereof the articular surface does 

 not encroach. Owing to the greater length of the neck and the lesser 



