The term hæmaturia is applied to blood in the urine from whatever part of the urinary passages it may come, whether the bladder, ureters, kidney, or even urethra; whereas the blood in primary hæmoglobinuria always comes directly from the kidney. In this paper I shall confine myself to the consideration of renal hæmaturia and hæmoglobinuria in the strict sense of the term; nor will I include such renal hæmaturia as constantly occurs in the first stage of acute Bright's disease. Emphasizing again that all primary hæmoglobinurias are renal, it is {105} important to be able to say of a given hæmaturia whether it is renal or not. Even coarse methods are often sufficient to settle the question. Blood from the kidney, so far as my experience goes, is never discharged in the shape of clots, at least large enough to be recognized as such by the naked eye. More frequently coagula of blood are passed when hemorrhage takes place into the pelvis of the kidney. These coagula generally cause severe pain in their descent, and by this symptom are distinguished from coagula from the lower part of the ureter and bladder. The smoky hue, which is characteristic of the presence of small quantities of blood in an acid urine, affords presumptive evidence that the blood is renal in its origin, because the conditions which are associated with blood from other parts of the genito-urinary tract are very apt to be associated with an alkaline urine, to which blood imparts a bright-red hue. This is, however, not invariable, as smoke-hued urine may be due to admixture of blood from the bladder and parts of the genito-urinary tract other than the kidney. The microscope affords valuable assistance in determining the source of blood in the urine. In addition to blood-discs or their molecular débris, tube-casts made up of cemented blood-discs or their débris are very constantly, although not invariably, found in such urine. This evidence is conclusive, and, although sometimes wanting, the invariable absence of clots from blood descended from the kidney, together with the absence of irritation of the bladder, makes it usually quite easy to recognize a renal hæmaturia. It is scarcely necessary to say that all urine containing blood or hæmoglobin contains albumen, the quantity varying with that of these substances present. Any further deviations from the normal composition of the urine are, in the main, due to admixture of other constituents of blood. Causes which give rise to Hæmaturia and Hæmoglobinuria.