Selected monographs.

Date:: 1888

Catalogue details

Licence: Public Domain Mark

Credit: Selected monographs. Source: Wellcome Collection.

156/440 (page 138)

and it therefore follows that perfect urine represents a mix- ture of a transuded with a secreted solution. Now if the fluid which escapes from the Malpighian tufts be a transudation^ it must necessarily contain the constituents common to all transudations—that is to say^ besides water there are the materials held in solution in the blood-plasma, in proportion of course to their capacity for filtration, and, therefore, not merely salts, traces of urea, &c., but also albuminous substances (serum-albumin and globulin). For there is no transudation without albumen, and if a fluid con- taining albuminous matters in solution filters at all through an animal membrane, the albuminous substances will like- wise pass through in a quantity corresponding to their capacity for filtration, such capacity being usually slight, the quantity also being subject to variations under difierent conditions. These conditions are : the quality of the mem- brane, especially its thickness, the concentration of the solu- tion, the salts it contains, its temperature and the pressure under which filtration goes on. As these conditions undoubtedly vary in different parts of the body, there need be no surprise at the differences as regards quantity of albumen in the transudations. Those normal transudations in particular which are separated from the capillaries by epithelium, such as the aqueous humour, the cerebro-spinal fluid and the endo-lymph, contain so little albumen that they are often set down as almost non-albuminous. For the same reason the transudation from the glomeruli must likewise be considered as only very slightly albuminous, but certainly not as absolutely free from albumen. It is well known that the older theories of Kiiss, v. Wittig and Henle assumed that the glomerular transudation contains albumen. In order to explain the non-appearance of this substance in normal urine, the idea was suggested that the epithelium of the uriniferous tubules withdraws the albumen from the passing fluid. The correctness of this last view has never been thoroughly demonstrated, but just as little has it been effectually controverted. It used to bo asserted that degeneration of the epithelium is not followed by albu-