METABOLISM IN DISEASES OF BONES AND JOINTS 757 



Calcium balance experiments on milking cows indicate that the same 

 kind of flux from the bones takes place during lactation (Forbes, Beegle, 

 Fritz, Morgan and Rhue(o-)(6)). 



As to the great need of lime salts during infancy, observation shows 

 that, weight for weight, a five months old infant requires from two to 

 five times as much calcium as an adult. 



A factor contributing to the decalcification of the skeleton at times 

 when there is a need of calcium elsewhere in the body is the ease of 

 bone catabolism compared with difficulty of bone anabolism. This is 

 shown by the fact that when there is a negative calcium balance, as in 

 lactating cows, it seems impossible to change this into a positive balance 

 by the administration of calcium salts. The bone readily gives up its 

 calcium but, even when its calcium store is somewhat depleted, does not 

 readily lay on new calcium (Forbes, Halverson and Morgan). 



As further chemical evidence in this direction, regarding calcium 

 metabolism during pregnancy, we have the observation of Neumann 

 (&) showing a retention instead of a loss of calcium, in a patient with 

 osteomalacia during pregnancy; there was also a retention of phosphate. 

 In this case calcium phosphate was leaving the skeleton, but, since it was 

 going to the fetus, it did not show up as a negative balance. (Table 26.) 



TABLE 26 



CALCIUM AND PHOSPHATE BALANCE DURING PREGNANCY 



That a healthy fetus can develop in a woman who has osteomalacia, 

 and who is not, therefore, without severe consequences to her own tissues, 

 in a condition to give up lime salts is not surprising, in view of the 

 results of Jaegeroos, who showed in experiments on dogs that a fetus 

 can develop at the expense of the mother even when there is a negative 

 phosphorus, nitrogen, and salt balance in the metabolism of the mother. 

 And Dibbelt showed that puppies can develop normally in utero, 

 while the mother lives on such a low calcium diet as to produce osteo- 

 malacia. That is to say, when there is not enough material in the food 

 for the mother alone, the fetus continues to grow, and the growth is at 

 the expense of the tissues of the mother, even if she is not in a condition 

 to give up material. * 



Histological investigations, too, are in agreement with the chemical 

 in indicating a flux of calcium salts from the bones of the gestating 

 mother. Thus Hanau found changes similar to osteomalacia at post- 



