PARATHYROID GLANDS 643 



whole, we arrive at the conclusion that the main fact thus far established 

 is the diminution of the contents of the tissues, especially of the nervous 

 tissues, in calcium, due probably to calcium withdrawal by acid bodies that 

 tend to accumulate when parathyroid insufficiency occurs. An alkalosis 

 may also, sometimes, diminish the available active calcium. The exact 

 explanation of the vice of intermediary metabolism that causes the acidosis 

 or the alkalosis is as yet wanting, though the latter may be due in some 

 cases to overventilation (Grant and Goldman), in others to sodium bicar- 

 bonate intravenously administered (Harrop; Howland and Marriott). 



Potassium and Sodium*. Many of those who lay emphasis upon the 

 calcium deficiency of the nerve tissues in tetany believe that the hyperex- 

 citability that accompanies it is due to the irritating effects of potassium 

 ions, sodium ions, or both, that remain "unbalanced." On discussing car- 

 bohydrate metabolism in tetany (vide supra), the opinion of Brown and 

 Fletcher is that proprietary foods and superheated carbohydrate foods 

 when fed to infants cause tetany by disturbing the balance between the 

 "sedative" and the "irritating" kations. Indeed, these authors would seem 

 to ignore the parathyroid entirely as a factor in the tetany of childhood, 

 though it is not improbable that, in this syndrome, parathyroid insuffi- 

 ciency and disturbed kation balance may be in some way linked together. 



Loeb's studies showed that calcium ions depress neuromuscular excit- 

 ability, but they also indicated that the muscles lost their excitability en- 

 tirely if sodium ions were withdrawn from them. Rhythmical contrac- 

 tions of skeletal muscles occur when sodium ions and calcium ions are 

 present in concentrations that lie within certain definite limits. Salts of 

 magnesium can, like salts of calcium, inhibit the stimulating effects of 

 solutions of sodium chloride. The results obtained by Joseph and Meltzer 

 in the inhibition of tetany symptoms by the injection of solutions of sodium 

 chloride were referred to above. 



J. B. MacCallum proved that kations of the alkali metals exert an im- 

 portant influence upon the neuromuscular mechanisms concerned in in- 

 testinal peristalsis. Thus, peristalsis could be inhibited by salts of potas- 

 sium and it could be increased by solutions that precipitate calcium. 



Biedermann (1898) observed that the heightened excitability produced 

 in muscle by sodium chloride solution is greatly increased by the addition 

 of Na 2 CO 3 , Na 2 SO 4 or NaOH. He was inclined to attribute the increase 

 to a specific effect of the sodium ion. 



The therapeutic administration of solutions of sodium bicarbonate has 

 been known to call forth attacks of tetany. Thus Howland and Marriott 

 (1918) report three instances in children, and Harrop (1919) reports an 

 instance in an adult. 



Obviously, attention in tetany should be directed from now on not only 

 towards the kations of calcium and magnesium salts but also towards those 

 of potassium and sodium salts. 



