I have nothing to say on changes of mental state due to loss of thyroid activity; the psychosis of cretinism [is well defined and widely known. But I venture to think that the mental changes of exophthalmic goitre are equally defined and not perhaps as widely realized. If this be so, if there are such distinct types of mental aberration, in marked antithesis to each other, which accompany two pathological states of the thyroid, perhaps also in antithesis, this is sufficient to give the subject a place in our discussion.