On the Crystalline Compound Containing Iodin Which Occurs in the Thyroid

IT is well known that desiccated thyroid gland exerts a marked physiologic activity when administered to the normal animal and man, and that the removal of the thyroid is followed by profound changes. The extremes of thyroid disturbance are seen in the two syndromes, exophthalmic goiter and myxedema; and between these are many indefinite or borderline conditions so that thyroid disturbances present a confusing mass of evidence which is not easily classified. Clinically, the cases have been classified and a basis of diagnosis established, and much light has been thrown on the progress of the disease of exophthalmic goitre. From clinical observations the thyroid has been supposed to have a secretion which contains a substance or substances possessing certain physiologic activity; but the acceptance of such a theory in itself erects a barrier beyond which the clinician cannot go. The only passage of that barrier is by a method which will unlock the constituents of the thyroid secretion and separate the active substances in pure form. Definite conclusions could not be arrived at as long as these substances were known only by the symptoms produced by their presence or absence.