Blumgart and his co-workers1 have shown the close relationship that exists between the height of the metabolic rate and the velocity of the blood flow. This relationship was demonstrated on hypothyroid and hyperthyroid patients with the use of the radium method2 for the determination of the speed of the flow of blood. These observations were abundantly confirmed by Tarr, Oppenheimer and Sager3 and by Gargill,3a who used the sodium dehydrocholate method4 in studying circulation time.
The conception that the amount of work done by the heart is partly determined by the metabolic rate has been substantiated and clinically applied in recent years. It has become a well established fact that when serious heart disease is associated with hyperthyroidism the cardiac embarrassment is grossly aggravated when the level of the metabolism is high and is much improved when the metabolic rate is lowered.5 This improvement