METABOLISM IN DISEASES OF BONES AND JOINTS 751 



bones, of many pregnant women showing no evidence of abnormal bone 

 changes during life, is in accord with the conception that the osteoid tissue 

 is newly laid down bone, and not old decalcified bone, for he, too, found 

 osteophytes in this tissue. Several older writers mention the finding of a 

 mild grade of osteomalacia in apparently healthy pregnant women, but 

 their findings seem to have made no impression. The facts have been 

 more recently confirmed by Wild. 



Another bit of evidence to support the theory of bone metabolism 

 outlined here, is afforded by Dibbelt's observation, that when recovery 

 from osteomalacia, experimentally induced in pregnant dogs, takes place, 

 the decalcified bone substance present in the active stage does not later 

 become calcified; it is absorbed and replaced by new calcified bone. 



The findings is osteitis deformans indicate that the abnormal bone 

 is of the same or of a very similar character to that in osteomalacia. 

 Yon Recklinghausen(&) was the first to point out that osteitis deformans 

 may be regarded as a local osteomalacia. On the basis of histological 

 examination, Schmieden, Tashiro, and Higbee and Ellis, have inde- 

 pendently come to the same conclusion. 



Histological examination, structural evidence, alone could not be 

 conclusive regarding the physiological nature of the process. Whether 

 Yirchow or Cohiiheim was correct could only be a matter of conjecture 

 until the physiological chemical evidence became available. The his- 

 tological evidence is, however, in accord with the chemical evidence in 

 indicating that the process in osteomalacia consists in a replacement 

 of the normal bone by new calcium-free bone, or bone poor in cal- 

 cium. 



Summary. To sum up our conclusions concerning the process in 

 osteomalacia, osteoporosis, osteitis deformans, rickets, and similar condi- 

 tions: The skeleton is made up of live tissue undergoing metabolism. 

 The bones are the seat of an uninterrupted and coincident process of 

 apposition and absorption throughout life. During infancy and child- 

 hood, as the uncalcified bone is gradually absorbed, the new bone laid 

 down to replace it becomes progressively richer in lime salts ; the rate 

 of apposition of lime salts to the bone is more rapid than absorption from 

 the bone. If this is not the case, and the new bone which should contain 

 lime salts is free from lime, the soft osteoid bone bends under the weight 

 of the body, the child becomes rickety. Bone metabolism is going on 

 too in later life, and if the anabolism of lime-containing bone does not 

 keep pace with its catabolism, the bones become poorer in lime salts ; when 

 this condition is extreme, the bones become soft. In old age, when anabolic 

 processes are retarded, a condition of increased metabolism of bone may 

 not be followed by increased apposition of even lime-free osteoid tissue, 

 and the result may be the condition of osteoporosis, known as senile 

 osteomalacia. The abnormal condition may be circumscribed, affecting 



