GROWTH AND REPARATION OF BONE. 363 



Growth of Bone. 



The long bones increase in length principally at the expense 

 of the cartilage intervening between the shaft and the epiphyses; 

 this constantly growing in the longitudinal direction, and giving 

 place to bone. But the growth of the short bones, and of the long 

 ones in thickness, has been regarded as a difficult subject to com- 

 prehend. The difficulty has, however, arisen from the erroneous 

 assumption that the osseous tissue, once developed, undergoes very 

 slight, if any, interstitial changes. Tomes and De Morgan have 

 shown (p. 325) that very active processes of disassimilation and re- 

 generation occur in the bone-substance. But, once admitting this 

 fact, there is no more difficulty in understanding how a bone than 

 how a muscle or any other organ increases in size, whether in all 

 or only in particular directions. 



Much stress has been put upon experiments with madder upon 

 young animals, in connection with this question. 1 This coloring 

 matter has a strong affinity for the phosphate of lime in the bones, 

 and hence, when given in the food, imparts to them a pink color; 

 and it was assumed that it combines with only the osseous tissue 

 which is formed while the madder is being taken by the animal. 

 It has, however, been proved by Brulle' and Hugueny that it colors 

 all the osseous tissue, even in adult animals, within a certain dis- 

 tance of the bloodvessels; and that the color remains in adult bones, 

 though it is again removed in growing animals. Very little im- 

 portance, .therefore, can be attached to these experiments, except so 

 far as that, when rightly interpreted, they also show (contrary to 

 what had been meanwhile assumed), that a very active metamor- 

 phosis is constantly going on in the osseous tissue, at least till the 

 osseous system has attained to its full development. 



Reparation of Bone. 



Osseous tissue is more perfectly regenerated than any other tissue 

 whatever. This fact may be associated with another viz., that no 

 other tissue can, in case of the long bones especially, at all supply 

 the place of the true osseous tissue ; so that nothing less than a 

 complete regeneration of the original tissue is compatible with the 

 continued function of the injured bone. 



1 In very young animals a single day serves to color the entire substance of the 

 bones. 



