A point of real difficulty of diagnosis, and great importance for treatment and prognosis, is the distinction between simple polyuria not excessive, but attended by constitutional symptoms, such as impaired nutrition, dyspepsia, and severe headache, from chronic interstitial nephritis, which often makes its appearance with similar symptoms. Mistakes between these two affections have undoubtedly occurred, and can in many cases hardly be avoided except by reserving the diagnosis for a time. The similarity is rendered still more deceptive by the undoubted occurrence of a trace of albumen or a hyaline cast or two in cases of nervous disturbance, without justifying a diagnosis of progressive renal disease. High arterial tension also is likely to be found in both conditions. Nothing but repeated and careful examinations of the urine and of the circulation, especially at times when the nervous symptoms are less marked, and often a considerable amount of time, can fix the diagnosis. Hypertrophy of the heart, and even slight dropsy, will undoubtedly be extremely decisive symptoms, but are not likely to occur until after a time when the doubt no longer exists. In other cases it may be highly important to carefully exclude organic cerebral disease before making a diagnosis of simple polyuria. It is hardly appropriate to speak of a diagnosis from azoturia or phosphaturia, since these conditions are extremely likely to exist coincidently with typical polyuria and to make a part of the same disease. It is of much importance, however, to ascertain their presence with reference to the probable effect of the disease on the nutrition. In regard to the TREATMENT, it may be remarked, to begin with, that restriction of water, although naturally diminishing somewhat the discharge of urine, does not cure the disease, but, on the contrary, in many cases augments not only the discomfort of the patient, but tends to the dryness of the skin, dyspeptic and nervous disturbances, and emaciation. Patients may recover flesh, strength, and spirits on being allowed to drink ad libitum, even although the inconvenience of excessive urination be thereby somewhat increased. Sufficient food and drink should therefore be allowed, although a patient may be ordered to observe such moderation as will not put his powers of endurance to too severe a test.