I am unable to ascertain, from any traditionary treatment of this case, whether the habit of gyration originated in some diseased imagination; or was merely, as I believe is more frequently the case, a habit which he had acquired from long confinement in a small space. This habit was common in former times, when they were confined in cells, and had no airing grounds; and yet some writers, without attending to this circumstance, have called it a symptom common to insanity! in this way, many things have been called symptoms, which have been, in fact, indications of improper treatment. The peculiar states of excitement and depression, so striking in this case, and which is so common with the old insane, as to have been called the chronic type of the incurable, I shall endeavour to show, how, in many instances, it may be explained on a different principle. Dr. Halloran, in his practical observations on Insanity, says,—“Chronic insanity is that form of the disease, which, having passed through the acute and convalescent stages, has assumed the more permanent character, and is known by the frequent exacerbation of the original accession; also, finally, under circumstances of less violence, and with symptoms subacute in relation to the primary affection.” He adds,—“There are few Practioners of the most ordinary discernment, who will not feel themselves disposed to acknowledge that cases of insanity, precisely of this form, compose the greater majority of those committed to their care.” He further says,—“That these paroxysms are for the most part periodical in their approach; for though of shorter duration, they continue pertinaciously unyielding.” From the observations which I have to suggest, it will be seen, that I conceive in some instances, in opposition to Dr. Halloran, and some others, that the chronic type, or the paroxysms of some of the permanently insane, are merely an exhibition of the irregular increase in the stock of their animal spirits, and not an exacerbation or new accession of the disease: and that even, in many cases, where the alternating changes of excitement and depression are most striking, I believe they first originated in those fluctuations of the animal spirits, common to all of us; in some instances, it is true, (and the case last described is one,) singularly modified, not merely by the state of mental alienation, but by circumstances connected with their confinement. Before, however, I endeavour to explain these singular modifications, it appears necessary to premise some observations on one of the causes which conspires to produce them, which cause is connected with the atmosphere.