It has been known for some years that certain mineral acids such as HCl, and acid producing salts such as CaCl2 and NH4Cl are effective agents in the treatment of infantile tetany, and have also been successfully employed in cases of experimental tetany.The effect of injecting HCl and CaCl2 or NH4Cl is the production of an acidosis. It seems from a survey of the literature on the subject, that the gross manifestations of tetany, even the most violent convulsions, are rather promptly relieved by slight changes in the reaction of the blood toward the acid side, and that such changes influence in some manner the calcium content of the blood.In view of these facts it was considered worthwhile to test the effect of administering CO2 to dogs in tetany, (1) in relation to relief of symptoms and (2) the effect upon the serum calcium level.Small rat and fox terriers were used as experimental animals. They were thyroparathyroidectomized and permitted to develop tetany. When the animals were prostrate they were bled...