SUTHEBLAND SIMPSON 



over a longer period for each animal than did those of MacCallum and 

 Voegtlin. Taking into account the fact that during tetany, animals fre- 

 quently refuse to eat, or do not retain food when it is administered to 

 them, he studied first the excretion of calcium and magnesium on a con- 

 stant diet and during fasting, and second the excretion of the same ele- 

 ments in animals on a constant diet succeeded by a fasting period during 

 which the parathyroids were removed. The animals were catheterized 

 daily at the same hour, and, to obtain constant amounts of urine, 350 

 cubic centimeters of distilled water was given in the twenty-four hours. 



It was found, first, that the brains of dogs dying in postoperative 

 tetany contain a slightly greater amount of calcium than do those of 

 normal dogs, and that the magnesium content is practically the same 

 in normal animals as in dogs in tetany. Second, the calcium and mag- 

 nesium content of the feces of normal and parathyroidectomized dogs 

 is similar; during fasting the excretion of both salts is diminished. 

 Third, the excretion of magnesium in the urine of dogs on a constant 

 diet, as well as in those fasting, runs parallel with that of calcium, while 

 the excretion of both salts is markedly diminished during fasting. After 

 parathyroidectomy, with the animal fasting, the elimination of magnesium 

 is greatly increased, while that of calcium remains unchanged. The in- 

 crease in magnesium elimination begins before tetany is observed. 

 Fourth, the increased elimination of magnesium indicates that, although 

 there is a disturbance of inorganic equilibrium, it is not limited to 

 calcium. Cooke suggests that the tetany represents a condition of altered 

 salt equilibrium in the nerve cells, brought about by disturbances in the 

 catalytic processes of the body, which increase the acid factors. His 

 experiments do not support the theory that the symptoms are due to the 

 calcium depletion of the cerebral cortex. 



Later Voegtlin and MacCallum (1911) stated, in view of the fact 

 that the symptoms are relieved by transfusion with a calcium-free sodium 

 chloride solution, and that some toxic substance is in all probability pres- 

 ent in the blood, the symptoms must be considered as due essentially to 

 calcium deficiency. 



Transfusion^ and Perfusion Experiments in Tetany. In 1912 Mac- 

 Callum showed that the galvanic hyperexcitability of the nerves, which 

 is a characteristic feature of tetany, is due to some change in the blood 

 induced by parathyroidectomy. By crossed circulation experiments, i.e., 

 connecting the blood vessels of an animal in tetany with those of the leg 

 <>f a normal animal, so that this was supplied with tetanic blood, it was 

 demonstrated that an excitability, identical with that found during tetany, 

 appears quickly in the nerves of the normal leg. When the tissues are 

 a.uain supplied with normal blood, the hyperexcitability disappears. Simi- 

 larly, the flooding of one leg of an animal suffering from tetany with 

 normal blood reduces the excitability of the nerves of that leg to the 



