METABOLISM IN DISEASES OF BONES AND JOINTS 749 



To summarize the results of metabolism experiments: We find that 

 the body is losing calcium and retaining magnesium and sulphur. These 

 results are in accord with those obtained by bone analyses, and confirm; 

 the supposition that in osteomalacia the process is not one of simple 

 passive halisteresis, but an active one of increased bone metabolism. Old 

 bone is destroyed and new bone laid down. But "the new bone is similar 

 to the organic matrix of bone, and is free from, or poor in, calcium phos- 

 phate, instead of which there is a partial replacement of the calcium phos- 

 phate by magnesium phosphate. 



The Results of Histological Examination. The next question to be 

 answered is whether or not histological investigations offer anything in 

 support of our chemical investigations. 



If we examine rachitic bones, we find osteoid tissue, that is, 

 the organic matrix of bone without the lime salts, at the junction of 

 epiphyses and diaphyses, as well as beneath the periosteum. If we 

 examine the bone in osteomalacia, we find similar osteoid tissue, 

 not, as in rickets, beneath the periosteum and at the boundaries 

 of epiphyses and diaphyses, but in the interior of the bone in proximity 

 to the Haversian canals. Yet, in the former case, the osteoid tissue has 

 been considered new lime-free bone, and, in the latter case, old decalcified 

 bone. There has been no good reason for this belief except the unjustified 

 assumption that, when once laid down, bone is dead tissue not undergoing 

 metabolism. 



Cohnheim(&) was the first to correctly describe normal bone metab- 

 olism and to express the opinion that the process in osteomalacia is not 

 one of halisteresis, but is essentially the same as that in rickets. Cohnheim 

 is worth quoting, no better statement of the process having yet been 

 made: 



(P. 630.) "In rachitic bones there is found at the junction of epiphysis and 

 diaphysis, as well as immediately beneath the periosteum in every situation, in short, 

 where new bone should be formed, a more or less compact, soft material, which is 

 sometimes gelatinous, varies in quantity with the intensity of the disease and is known 

 as osteoid tissue. This substance is nothing more or less than the organic ground 

 substance of bone, without the bone-earth which should be combined with it." 



(P. 631.) "As\to the histological appearance of the bones in true osteomalacia 

 . . . they consist in the substitution of osteoid zones for the typical osseous tissue. 

 These zones are not, however, situated beneath the periosteum and at the boundaries 

 of the epiphyses, as in rickets, but occupy essentially the interior of the fully formed 

 bone in immediate proximity to the Havesian canals." 



(P. 632.) "Lastly, we have to determine the nature of the zones of osteoid tissue 

 occupying the interior of the bones in osteomalacia proper. The most widely accepted 

 view is that this tissue originates in an active decalcification, that fully developed 

 normal bone had previously existed at the seat of the osteoid tissue, and has been 

 deprived of its lime salts by a pathological process. Accordingly, the process is repre- 

 sented as strictly analogous to the method of decalcification adopted, with a view to 

 microscopical examination of a bone." 



After expressing his disbelief in this commonly accepted view, he goes 

 on to say: 



