The work reported in this paper was undertaken at the suggestion of A. J. Carlson, primarily for establishing a biological test for the active principle of the thyroid gland in the blood.
A few years ago Hunt,1 by means of the acetonitril test, thought that he had a reliable test for the active principle of the thyroid in the blood. Later investigators (Carlson and Woelfel,2 Lussky3) failed to detect any active principle of the thyroid in the blood of the dog, and in rabbits and guinea-pigs in experimental hyperthyroidism by means of this test. Hunt studied the blood of clinical cases of exophthalmic goiter and obtained a positive test in two out of three cases. On the other hand, Carlson and Woelfel could not get a positive reaction in a case studied by them. Carlson also tested his own blood after having taken thyroid until toxic