A Method for Isolating the Renal Tubules of Mammalia

Two methods are available for ascertaining the size, shape, sequence and relations of the several parts of a renal tubule of mammalia, namely, reconstruction by the wax-plate method and maceration of kidney substance to an extent permitting isolation of tubules or tubule segments. Of these two methods that of reconstruction is the more satisfactory, within the limits of its applicability, since it permits of the reproduction of the several parts of a tubule in their normal relation and in permanent form. However, the complexity of the renal tubules, especially of adult mammals is such, that i t is necessary to have for purposes of wax-plate reconstruction, first, an unbroken and relatively long series of sections, extending through cortex and medulla, and not to exceed 5 micra in thickness, and second, to use a magnification of about 400 diameters. The limits of applicability of thc wax-plate method, Lherefore, is reached about with renal tubules taken from the kidneys of newly born or relatively young stages of the smaller mammals; the renal tubules of newly born rabbits and cats, thus reconstructed resulting in models reaching a length of between four and five feet. The size of the model which would result from reconstruction of a renal tubule of an adult mammal, but more especially the difficulty of tracing through an unbroken series of 150 to 250 sections the different parts of such a tubule, would relegate this method, under such conditions, to the position of one of the most difficult of technical procedures. The method of maceration is the older and has been very widely used. The rapidity and ease of its application, and the fact that large numbers of tubules or tubule segments are readily placed a t the disposal of the observer, commend it. However, the methods of maceration as npw very generally used are not without limitations, so that while the results of nearly all investigations dealing with form and relations of the several parts of the mammalian renal tubule are based on observations made with the aid of maceration methods, it has not been possible until very recently to even approach the isolation of a complete renal tubule in an adult mammal, all conceptions of their form and relations being