The composition of the blood is undoubtedly changed in most of the cases with cerebral symptoms. It is natural to look for such changes as {78} are due to perversion of the excretory function of the kidneys, and to ascribe the cerebral symptoms to the poisoning of the blood by urea, by urea transformed into carbonate of ammonia, or by the other excretory matters which should be eliminated by the urine. Moreover, it has been demonstrated that there is a very marked increase in the amount of urea contained in the blood in such cases. On the other hand, we find that suppression of urine with accumulation of urea in the blood may exist for a long time without cerebral symptoms if the suppression is due to obstruction of the ureters; that with chronic congestion of the kidney, puerperal convulsions, and diseased arteries urea is excreted in fair amount, although cerebral symptoms exist; and that even in cases of cerebral symptoms with chronic diffuse nephritis there may be no increase of urea in the blood. In most of the cases with cerebral symptoms, however, there are other changes in the composition of the blood, concerning the exact nature of which we are still ignorant. In most cases of chronic Bright's disease the patients become pale and the blood is thin and watery; and this is also often the case with chronic congestion of the kidney and with diseased arteries. In pregnancy the quantity of blood is said to be increased: in cholera a considerable part of the fluid portions of the blood is lost. Changes in the amount of blood in the brain may be due to lesions of the cerebral arteries or to contraction of these arteries; to changes in the arteries in other parts of the body; to organic disease or functional disorder of the heart; or to a change in the whole amount of blood contained in the body. It seems to me probable that the so-called uræmic symptoms are most frequently due to disturbances of the circulation of blood. Such disturbances of the circulation produce in the brain cerebral symptoms; in the lungs, dyspnoea; in the stomach, vomiting; in the kidneys, suppression of urine. With the atrophic form of chronic diffuse nephritis we have all the conditions necessary for an irregular circulation--hypertrophy of the left ventricle, diseased arteries, and hydræmic plethora. In the other cases with cerebral symptoms there are also conditions present capable of interfering with the circulation. Acute Parenchymatous Nephritis. PATHOLOGICAL ANATOMY.--The lesions of acute parenchymatous nephritis vary with the intensity of the inflammatory process. (1) Mild Cases.--The kidneys are of normal size and weight. The capsules are not adherent, the surface of the kidney is smooth, the cortex is of normal color or rather pale. The epithelial cells lining the convoluted tubes are swollen and granular.