Hæmaturia is due to a variety of causes, which may be local or general. Local hæmaturia is caused by wounds, blows upon the kidney, or falls in which the kidney receives the force of the blow, as in striking the edge of a fence in falling; from cancer of the kidney, impacted calculus, parasites, embolism, acute Bright's disease; also poisoning from carbolic acid, cantharides, and mustard. General causes of hæmaturia are malaria, purpura, scurvy, blood-dyscrasias due to continued and eruptive fevers, especially typhus fever and smallpox, septicæmia and pyæmia, and cholera. Finally, it must be admitted that there is a hemorrhagic diathesis manifested by hæmaturia and hæmoglobinuria. Primary hæmoglobinuria may be produced by any of the general causes just named, or by the prolonged inhalation of arseniuretted hydrogen and carbonic acid, and the introduction of numerous substances into the blood, as iodine, arsenic, etc. While a rupture of the blood-vessels of the kidney may be supposed to be at the bottom of a certain proportion of cases of hæmaturia, it is by no means a necessary condition of their occurrence, as it is well known that in inflammations there may be extravasations of blood without rupture of {106} the blood-vessels. There is implied, however, in all these conditions an alteration of the vessel-walls which permits such transudation. Indeed, Ponfick[1] goes so far as to say that even transudations of hæmoglobin through the blood-vessels of the kidney are impossible without the presence of serious diffuse nephritis. There is every reason to believe, however, that simple alterations of the blood are of themselves sufficient to cause such transudations. Take, for instance, the extravasations in purpura, which are not confined to the vessels of the kidney. It is impossible to conceive inflammatory conditions so general as would have to be presupposed in this disease. [Footnote 1: "Ueber die Gemeingefährlichkeit der essbaren Morchel," _Virchow's Archiv_, Bd. lxxxviii. S. 47.] Hæmaturia from Local Causes. It is unnecessary to consider in detail the local causes of hæmaturia. It is evident how injuries and blows upon the kidney, and impacted calculus may produce hemorrhage. The history of nephritic colic or of gravel in urine, along with blood, would suggest the latter cause. Nor is it necessary to detail the phenomena of hemorrhagic infarction which succeeds embolism and is the direct cause of hemorrhage into the tubules of the kidney. Hæmaturia is by no means a constant symptom in sarcoma and cancer of the kidney. A small amount of blood in the urine is a constant symptom in acute nephritis, where it is due to a rupture of the blood-vessels of the Malpighian tuft. It is accompanied by blood-casts and other symptoms of acute Bright's disease. Carbolic acid, cantharides, oil of mustard, and similar substances produce hæmaturia by causing congestion and inflammation of the kidney.