In Sir William Gull's classical description of “A Cretinoid State,” which we now call Myxódema, in 1873 he thus describes the mental condition of his first patient: ∗—“In the patient whose condition I have given above there had been a distinct change in the mental state. The mind, which had previously been active and inquisitive, assumed a gentle, placid indifference corresponding to the muscular languor, but the intellect was unimpaired.” He noticed “changes in the temper,” and assumed that the mental changes were pathological and a part of the disease. In Dr. Ord's almost equally classical paper, in which he gave the disease its present name,† he referred to the “slowness of thought,” the “long and diffuse letters” of one of the patients. In every full description of any case of myxódema that I have seen some such morbid mental change has been referred to. In the Report for 1888 of the Committee of the Clinical Society of London on Myxódema, the mental condition of the patients was inquired into, but there is internal evidence that the reporters did not all understand mental symptoms in the same light. Slowness of mental action was the symptom most common, for its absence was only noted in three of the 109 cases. Delusions and hallucinations are stated to have been present in 15 cases, or 14 per cent., and actual insanity in 24 cases, or 22 per cent. There is very frequent mention of morbid suspicions under the mental heading, and memory is usually stated to be impaired where reported on. In his experiments on monkeys, detailed in the report, Horsley specially refers to mental symptons that followed extirpation of the thyroid. He says the “mental operations, normal at first, soon diminished in activity, and then follow apathy, lethargy, coma.” “Gradually the intellect became duller, the energy of the animal diminished, and apathy alternating with idiotic activity resulted.”