THE SUPPORTING TISSUES. 



89 



repeated in a number of the irregular bones of the body, 

 which have on the outside some denser bone, while the 

 interior is more or less spongy. It will be recalled that 



Fig. 40. LONGITUDINAL SECTION OF THE HEAD OF THE FEMUR SHOWING THE CANCEL- 

 LATED STRUCTURE AT END, AND SOLID BONE OF SHAFT. (From a photograph by 



Zaaijer.) 



in the spongy part of all these bones, no less than in those 

 of the long bones, red marrow occurs. 



To discover the real structure of bone it is necessary to 

 grind a bone into an exceedingly thin section, so that it 

 may be viewed with a microscope. If such a cross section, 



