THE PARATHYROID GLANDS 533 



The electrical excitability of the peripheral nerves is also increased, 

 and this is one of the earliest signs observable and one of the most delicate 

 indications of diminished parathyroid function. The phrenic nerve may 

 be so sensitive as to be excited by the action currents of the heart, so that 

 the diaphragm twitches with each heart beat. Nevertheless, neither in 

 parathyroid nor in idiopathic tetany is the severity of the symptoms 

 directly proportional to the increased peripheral electrical excitability; 

 hence the latter does not indicate accurately the gravity of the condition. 



Hoskins and Wheelon in 1914 noted that after parathyroid extirpation 

 there is demonstrable a marked increase in the irritability of the sympa- 

 thetic nervous system. Their method was to determine the vasomotor re- 

 action of a given animal to nicotin, which is a selective sympathetic stimu- 

 lant, and then to remove the parathyroids and, after the development of 

 tetanic symptoms, again to determine the reaction. By this means it was 

 found that the nerve cells proper were affected. Similarly, the use of 

 epinephrin showed increased irritability of the myoneural junctions. An 

 augmented reaction to pituitrin was also interpreted as showing a similar 

 effect in the musculature proper. 



Changes in the central nervous system have been described in parathy- 

 roid tetany in the direction of cell chromatolysis. Edmunds says they are 

 similar to those observed after acute poisoning. 



Degenerative changes in the liver cells have been described by Gozzi 

 and others, but these probably result from the general effects on the 

 organism as a whole which follow the loss of the parathyroid glands, rather 

 than from any direct action. 



Experimental Attempts to Augment or Allay Parathyroid Tetany. 

 The second method of investigation previously mentioned has yielded little 

 positive information regarding the functions of the parathyroid glands. It 

 is recognized that grafting is frequently curative in cases of postoperative 

 tetany. Borcher (1919) says that a single large parathyroid is adequate 

 to obviate symptoms in the human subject. The operation on both donor 

 and recipient may be done under local anesthesia, and the best situation 

 for the graft is in one of the abdominal muscles. 



It is reported by many that tetany is relieved by the injection of the 

 extract, or by administration of the gland, fresh or desiccated, by mouth. 

 Assuming that the parathyroid produces an internal secretion, MacCallum 

 and Voegtlin attempted to obtain evidence of this and, if possible, to 

 isolate the active substance. The beneficial effects of transplanting para- 

 thyroids and of the injection of parathyroid extracts into animals in tet- 

 any have been reported frequently. Berkeley was successful in relieving 

 the symptoms of gastric tetany in a man thirty-nine years of age by the 

 administration of fresh ox parathyroid ground up with milk sugar and 

 given by mouth, and a similar preparation was effective in a case of sur- 

 gical tetany in man, reported by Putnam. 



