METABOLISM IN DISEASES OF BONES AND JOINTS Y67 



provoked osteomalacia in a pregnant rabbit by administration of thyroid 

 gland. Told and Sarvarat report one patient with both osteoma- 

 lacia and goiter, and have found eleven similar cases in the literature. 

 Such evidence is not very convincing. That there is a relationship of 

 some sort between bone metabolism and the thyroid gland is evident 

 from the failure to grow, and the delayed ossification (Schmidt) in cretin- 

 ism, the failure of normal skeletal development in thyroidectomized 

 animals (Biedl), and the more rapid bone formation and increased calci- 

 fication in thyroidectomized animals, to whom thyroidin has been admin- 

 istered (Bircher). 



A relationship between the hypophysis and osteomalacia has been as- 

 sumed on the basis of results of pituitrin therapy in this disease (Bab, 

 Neu; but the evidence is poor. The clinical changes in acromegaly, 

 especially the increased bone formation, and the osteoporosis which some- 

 times accompanies it (Trevelyan), indicate a relationship of some kind 

 between the hypophysis and bone metabolism. What little we know of 

 this subject is fully discussed in the chapter on the hypophysis. 



There appears to be a relationship of some sort between bone metab- 

 olism, and calcium metabolism, and the thymus. It has been observed 

 that thymectomy decreases the calcium content of the bone (Klose and 

 Vogt), increases the calcium excretion (Frankel(&)) and makes the 

 bones soft, flexible, and fragile (Basch, Klose(a) (6), Soli). 



The evidence connecting osteomalacia with the parathyroid glands is 

 the result of studies carried out in Professor Weichselbaum's laboratory 

 in Vienna, and is stronger than that connecting the disease with any other 

 gland. Erdheim(a) examined the parathyroids in six cases of osteo- 

 malacia, and found pathological changes in five of them. Todyo 

 found pathological changes in these glands in seven cases of osteomalacia, 

 and in eleven cases of osteoporosis ; as controls he examined also the glands 

 in twenty-four cases of other kinds of disease. In the same laboratory, 

 in carrying out postmortem examination of a patient, who showed no 

 symptoms of osteomalacia during life, Bauer discovered a small -tumor 

 of the parathyroid, and this led him to make a special examination of the 

 bones for evidence of osteomalacia. Osteomalacia was present. Very 

 thorough experimental studies were then undertaken in animals, and it was 

 found that in parathyroidectomized rats callus formation after fracture 

 is delayed (Erdheim(6)). 



It was found further, that the incisor teeth of rats grow fairly rapidly, 

 the dentin and enamel being laid down in layers (Erdheim(c)). 

 In cases of spontaneous rickets in these animals, a failure of calcification 

 of the dentin and enamel accompanies the rickets (Erdheim(6)). Ex- 

 amination of the growth and calcification of the teeth gives, therefore, 

 a fairly precise estimate of the durajtion and extent of any disturbance of 

 calcium metabolism. After removal of the parathyroids, the dentin and 



