258 JOHN C. KOCH 



crossed :it rij2;ht angles by ii more widely spaced system of 

 trabeculiie. 



A. Structural features. The structural features of iiiost im- 

 portance in this section are: 



1. The sp()nj;y bone is most closely arranged in the head of 

 the fenmr, and it becomes thinner and more widely spaced as 

 the lesser trochanter is approached. 



2. The thinning of the trabecular structure begins immedi- 

 ately below the articular surface of the head, 



3. The change of the heavy compact bone, on the posterior 

 side below the trochanter, to the system of light trabeculae which 

 crosses the lesser trochanter and fuses to form the compact bone 

 of the neck of the femur. 



3. The serial transverse sections of the upper femur. T ese 

 sections made at ^-inch intervals, are so numbered that the dis- 

 tance in quarter-inches, measured along the neutral axis, from 

 the proximal end is indicated by the number of the section. 



In Plates 1 and 2 only the alternate transverse sections of the 

 upper femur are showm. These sections from 2 to 20 confirm 

 the observation made of the sagittal section, previously de- 

 scribed: that the trabecular structure distal to the head gradu- 

 ally becomes lighter after the lower level of the articular surface 

 of the head is passed. 



The cross section of the head of the femur is practically cir- 

 cular, and it is made up entirely of spongy bone except for the 

 thin shell of compact bone forming the articular surface. Sec- 

 tions through the neck show a gradual thickening of the outer 

 shell to form the shaft, with a parallel decrease in the density 

 of the spongy bone, as the sections are taken more and more dis- 

 tal to the head. In the neck there is a marked decrease in the 

 gross area of the cross section, which reaches a minimum in f-ec- 

 tion 8. Referring to table 5, it wdll be seen that the area of com- 

 pact bone in this section, including the equivalent area of the 

 spongy bone, is less than that of any other section of the entire 

 femur. The marked variations not only of relative density of 

 the spongy bone, but of the size and shape of cross section that 

 are seen in the successive sections of the heatl and neck are of 



