Generally we have been content to employ for the urine the division used for blood albumin bodies, and—following the proposal of Hof meister—to designate as globulin that portion which can be precipi tated by partial saturation with ammonium sulphate, arid as albumin that portion which is only precipitated by complete saturation. But here we have not taken advantage of the knowledge that blood-globulin is very probably a complicated mixture of several albumin bodies. Instead two divisions have been accepted for clinical purposes, i.e., the so-called fibrin and euglobulin, which precipitate by saturation with 25 per cent. ammonium sulphate, and the pseudoglobulin, which pre cipitates by saturation with from 25 per cent. to 3:3 per cent. ammonium sulphate. Although it is somewhat precarious to identify albuminous bodies, one from another by precipitation limits, the matter is so far tolerably clear, but practically it is complicated by the presence in the urine of an albuminous substance which is thrown down by acetic acid, without heating. The qualitative test, which has a certain clinical value, is easily made. Fill two test-tubes to the same height with the urine to be tested, and after adding to both a few drops of dilute acetic acid, shake thoroughly- for some minutes. This is necessary because precipitation does not occur immediately. Now dilute with three or four parts of water, and to one of the test-tubes add a few drops of solution of ferrocyanide of potash. When the two tubes are now held against a dark back-ground one can not only determine the presence or absence of albumin precipitated by acetic acid, but can even estimate its proportion as compared to the total albumin. Dilution with water after the acetic acid is added is necessary to prevent the precipitation of uric acid in a highly concentrated urine, which might simulate the albumin sediment. This source of error in the urine of persons suffer ing with diphtheria has been pointed out by Langer.
Opinion as to the nature of the albumin body precipitated by acetic acid has undergone constant change, and even now its position is uncer tain. _Monier, to whom we are indebted for elaborate investigations,
regarded it not as albumin, but as a combination (salt) of albumin. F. „hillier designated it a globulin, in which both his pupils, ritaehelin, and also Oswald agreed with him. Lettbe and his pupils identified it as euglobulin. Rostoski, who believes it to be exceedingly diffusible, would like to see it excluded from the class of globulins. In opposition stand Obermayer and Keller wlao consider this albumin body to be nucleo-albumin, i.e., a product of the nuclein substance. This they have inferred from the quality of being precipitated by acetic acid and because it is sometimes possible to demonstrate the presence of phos phorus. The first inference i.s not conclusive because nucleo-albumin posses the quality of precipitation by acetic acid in common with a long series of other albumins; and the positive proof of the presence of phos phorus can be used in support of the nucleo-alburnin nature of an albuminous body, only when phosphorus is detected after its pure exhi bition. The detection of phosphorus in an albuminous substance pre cipitated by acetic acid will always leave room for doubt whether the phosphorus did not come from an admixture, since the extraction of an absolutely pure albuminoid body from the urine is scarcely- possible.
My own opinion is that the positive identification of the albumin body is not of much importance, because there remains the possibility that the substance is not always the same chemical entity in the A•arious affections which lead to its excretion. But it was necessary- to discuss the tolerably complicated conditions because the albuminuria of the newborn as well as the orthotie form of albuminuria are accompanied by the excretion of the albuminous substance w-hich is precipitated by, acetic acid, and because the chemical ambiguity of this precipitate has led to differences in estimating tbe significance of the symptom.