THE PAEATHYROID GLANDS 537 



have asserted that animals fed on an exclusively milk diet show the 

 symptoms less violently than those fed mainly or entirely on meat. 



The changes in the teeth of rats first described by Erdheim (&), already 

 alluded to, also bear on this point, as indicating some profound altera- 

 tion in the character of the calcium metabolism of the body caused by 

 the loss of the parathyroids. Erdheim (c) noted also that callus formation 

 was retarded on account of the deficient deposition of calcium salts. 



Calcium Medication in Tetany. MacCallum and Voegtlin carried 

 out their experiments on dogs, inducing tetany by extirpation of thyroids 

 and parathyroids. They found that the injection of a solution of a salt 

 of calcium into the circulation of an animal in tetany promptly checks 

 all the symptoms and restores the animal to an apparently normal con- 

 dition. Tetany may be regarded as an expression of the hyperexcitability 

 of the nerve cells, due to the withdrawal of calcium from them. The 

 effect of subcutaneous injection of calcium, or of giving it by the mouth, 

 is the same as that of intravenous injection, but it appears more slowly. 



These observers, during the course of their animal experimentation, 

 were given the opportunity of applying this treatment to a case of 

 postoperative tetany in the human subject. In this case calcium lactate 

 was administered in frequent and quite large doses, with the result that 

 the tetany disappeared in the course of a single day. When the calcium 

 medication was withheld for two or three days, the symptoms of tetany 

 reappeared, only to disappear on the administration of calcium. They 

 also found that the injection of magnesium salts will suppress the symp- 

 toms of tetany, although its effects are somewhat confused by the ataxic 

 and anesthetic action of magnesium, as pointed out by Meltzer. The 

 injection of sodium and potassium salts, on the other hand, had no bene- 

 ficial action, but tended rather to intensify the symptoms. 



Calcium Excretion in Tetany. MacCallum and Voegtlin also studied 

 the metabolism of these animals and found, during tetany, a marked 

 reduction in the calcium content of the tissues, especially of the blood 

 and brain. There was also found to be a greater output of calcium 

 in the urine and feces on the development of tetany, an increased output 

 of nitrogen, and of ammonia in the urine, with a higher ammonia ratio. 

 The ammonia content of the blood was also raised. .These investigators 

 drew attention to the remarkable difference between the changes in metab- 

 olism respectively after thyroidectomy and parathyroidectomy. There 

 is evidence of some kind of acid intoxication, but its effects are not neu- 

 tralized by the introduction of alkaline sodium salts. In general, they 

 say, the role of calcium salts in connection with tetany may be conceived 

 as follows : a These salts have a moderating influence upon the nerve ce!L 

 The parathyroid secretion in some way controls the calcium exchange in 

 the body. It may possibly be that, in the absence of the parathyroid se- 

 cretion, substances arise which can combine with calcium, abstract it from 



