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646EFFECT OF DICUMAROL and in several instances, both at 300 mm and at 250 mm, the respiratory movements of the untreated rats were too irregular to be counted with accuracy. This latter irregularity consisted of periodic breathing of the Cheyne-Stokes type, the periods of complete apnea being very long. The differences in respiratory rates of the contrasting groups, both at 300 mm and at 250 mm, are highly significant when analyzed by Fisher's t test.Rats treated with nicotinic acid or its amide were found to survive until they reached a barometric pressure of 75 mm Hg (equivalent altitude, 53,800 feet) ; untreated Summary.controls died at an average pressure of 93 mm Hg (49,275 feet). Statistically, the differences are probably significant.The tachypnea developing a t low barometric pressure is much less in treated than in untreated rats. Preliminary injection of 1 mg nicotinic acid was followed by an increase in respiratory rate of only 22% at 300 mm Hg as opposed to approximately 80% in untreated controls. Differences of comparable magnitude were noted at pressures of 300 and 250 mm Hg following the administration of nicotinamide. Statistical analyses indicate that these differences are highly significant.

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