Seat of Action in Tetany after Parathyroidectomy. 23 



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The seat of action in tetany after parathyroidectomy. 



By W. G. MACCALLUM. 



[From the Department of Pathology of the College of Physicians and 

 Surgeons, Columbia University.] 



Both the immediate cause and seat of tetany are still obscure. 

 It has been suggested, though never proven, that a poison must 

 circulate in the blood to cause the tetanic twitchings. It has also 

 been suggested that these twitchings may result from a lack of 

 calcium in the circulating fluids. It has been shown that tetany 

 does not appear in a limb to which the nerves have been cut. It is 

 conceivable that this is due to the fact that no impulses reach 

 that limb from the spinal cord. The present experiments show 

 that if the nerves be cut during tetany, their electrical excitability 

 remains the same as that of the intact nerves on the opposite 

 side. Further, it is shown that if the nerves be cut before the 

 development of tetany, they become hyperexcitable to an extent 

 which equals that of the intact nerve on the opposite side, although 

 they are quite separate from the spinal cord. Since degeneration 

 occurs within two or three days, such observations must be made 

 with due regard to this fact. The peculiar character of this rise 

 in the excitability is seen in the figures obtained for the cathode 

 and anode opening shocks to which the nerves become especially 

 excitable. In complete anemia or after the death of the animal 

 there is a period of about one half hour during which this char- 

 acteristic rise in the excitability of the nerve to the cathode and 

 anode opening shocks appears. Nevertheless, the excitability of 

 the nerves is, throughout this period, very much lowered and the 

 curve is in no way comparable, therefore, to that in tetany. 



Transfusion of the blood of an animal in tetany into the vessels 

 of a normal animal has not succeeded in producing a characteristic 

 tetany nor even a marked change in the excitability of the nerve. 



This is probably partly due to inadequate technique and partly 

 to the action of the normal dog's parathyroids. If the leg of a 

 normal dog be isolated, with the exception of the nerves which 



