In a paper which has quite recently appeared Diabella has investigated these relations very thoroughly, and his results partly correct, and partly confirm those of Hammerschlag. Diabella found from his comparative estimations that differences of 10% haemoglobin (Fleischl) correspond in general to differences of 4.46 per thousand in the specific gravity (Hammerschlag's method). Nevertheless with the same amount of haemoglobin, differences up to 13.5 per thousand are to be observed; and these departures are greater the richer the blood in haemoglobin. Regular differences exist between men and women; the latter have, with the same amount of haemoglobin, a specific gravity lower by 2 to 2.5. Should the parallelism between the number of red blood corpuscles and the amount of haemoglobin be considerably disturbed, the influence of the stroma of the red discs on the specific gravity of the blood will then be recognisable. Diabella calculates, that with the same amount of haemoglobin in two blood testings, the stroma may effect differences of 3-5 per thousand in the specific gravity. Hence the estimation of the specific gravity is often sufficient for the determination of the relative amount of haemoglobin of a blood. It is only in cases of nephritis and in circulatory disturbances, and in leukaemia, that the relations between specific gravity and quantity of haemoglobin are too much masked by other influences. The physiological variations which the specific gravity undergoes under the influence of the taking in and excretion of fluid do not exceed 0.003 (Schmaltz). From what has been said, it follows that all variations must correspond with similarly occurring variations in the factors that underlie the amount of haemoglobin and the number of corpuscles. More recent authors, in particular Hammerschlag, v. Jaksch, v. Limbeck, Biernacki, Dunin, E. Grawitz, A. Loewy, have avoided an omission of many earlier investigators; for besides the estimation of the specific gravity of the total blood, they have carried out that of one at least of its constituents, either of the corpuscles or of the serum. The red blood corpuscles have consistently shewn themselves as almost exclusively concerned with variations in the specific gravity of the total blood; partly by variations in number, or changes in their distribution; partly by their chemical instability; loss of water and absorption of water, and variations in the amount of iron.