THE FEMUR, OR THIGH-BONE. 



189 



planes are arranged in a curved form, in order to strengthen the bone when exposed 

 to pressure in all directions. In the midst of the cancellous tissue of the neck is 

 a vertical plane of compact bone, the femoral spur (calcar femorale) which com- 

 mences at the point where the neck joins the shaft midway between the lesser 

 trochanter and the internal border of the shaft of the bone, and extends in the 

 direction of the digital fossa (Fig. 129). This materially strengthens this portion 

 of the bone. Another point in connection with the structure of the neck of the 

 femur requires mention, especially on account of its influence on the production of 

 fracture in this situation. It will be noticed that a considerable portion of the 

 great trochanter lies behind the level of the posterior surface of the neck ; and if a 

 section be made through the trochanter at this level, it will be seen that the 

 posterior wall of the neck is prolonged into the trochanter. This prolongation is 

 termed by Bigelow the " true neck," l and forms a thin, dense plate of bone, which 

 passes beneath the posterior intertrochanteric ridge toward the outer surface of 

 the bone. , 



In the lower end the cancelli spring on all sides from the inner surface of 

 the cylinder, and descend in a perpendicular direction to the articular surface, the 

 cancelli being strongest and having a more accurately perpendicular course above 

 the condyles. In addition to this, however, horizontal planes of cancellous tissue 

 are to be seen, so that the spongy tissue in this situation presents an appearance of 

 being mapped out into a series of rectangular areas. 



Articulations. With three bones : the os innominatum, tibia, and patella. 



Development (Fig. 130). The femur is developed by five centres: one for the 

 shaft, one for each extremity, and one for -each trochanter. Of all the long bones, 

 except the clavicle, it is the first to show traces of ossification : this commences in 

 the shaft, at about the seventh week of foetal life, the centres of ossification in the 

 epiphyses appearing in the following 

 order : First, in the lower end of 

 the bone, at the ninth month of foetal 

 life 2 (from this the condyles and 

 tuberosities are formed) ; in the head 

 at the end of the first year after 

 birth ; in the great trochanter, during 

 the fourth year ; and in the lesser 

 trochanter, between the thirteenth 

 and fourteenth. The order in which 

 the epiphyses are joined to the shaft 

 is the reverse of that of their appear- 

 ance: their junction does not com- 

 mence until after puberty, the lesser 

 trochanter being first joined, then 

 the great, then the head, and, lastly, 

 the inferior extremity (the first in 

 which ossification commenced), which 

 is not united until the twentieth 

 year. 



Attachment of Muscles. To 

 twenty-three. To the great tro- 

 chantef : the Gluteus medius, Gluteus 

 minimus, Pyriformis, Obturator inter- 

 nus, Obturator externus, Gemellus 

 superior, Gemellus inferior, and 

 Quadratus femoris. To the lesser 

 trochanter : the Psoas magnus and 

 the Iliacus below it. To the shaft : 



Appears at 

 year; joins shaft *$ 

 about 18th year. 



Appears at 

 9th month 

 (foetal). 



Appears at end 

 of 1st year ; 



joins shaft about 

 18th year. 



Appears ISth-lJ^th year ; 

 = joins shaft about 18th 

 J> year. 



Joins shaft at 20th 

 year. 



Lower extremity. 



FIG. 130. Plan of the development of the femur, 

 five centres. 



P.y 



1 Bif/elow on the Hip, p. 121. 



2 Tins is said to be the only epiphysis in which ossification begins before birth ; though accord- 

 to some observers, the centre for the upper epiphysis of the tibia also appears before birth. 



