MINUTE STRUCTURE. - In this division of our subject, we have to consider, in succession, the following structures, 1st, The fibro-cellutar matrix ; 2ndly, The tubes, their course, division, and termination ; 3rdly, The Malpighlan bodies, their connexion with the blood-vessels, and with the tubes ; 4thly, The epithelium, in different parts of the surface over which the urine passes, com mencing with that of the Malpighian bodies, and terminating with that of the pelvis and ureter.
The fibro-cellular matrix of the kidney has been well and accurately described by Professor Goodsint It exists throughout every part of the renal structure. (Fig. 149, c) represents compartments, occupy the position of the original interlobular fissures in the embryo kidney, and are analogous to the deep layer of the fascia with its interlokular volongations nected, and a misapprehension of which may lead, as it has led, to serious practical errors.
a portion from the cortical substance.) It is best examined in a thin section which has been macerated in water for a few minutes, so as to wash away the tubes and Malpighian bodies. The matrix then appears in the form of a fibrous network, the meshes of which have, for the most part, a circular outline. The smaller meshes are of pretty uniform size, and are accurately filled by the tubes, each tube in its tortuous course passing through very many of the cells formed by this curious and beautiful structure. The meshes do not occupy any one plane or posi tion rather than another, but in whatever di rection the section of the cortical substance is made, the same regular network presents it self. When the tubes are in they often appear to be mapped out, as it were, into re gular circular or oval portions ; an appearance which has, doubtless, confirmed some observers in the erroneous notion that the tubes termi nate in blind extremities. This apparent iso lation of the different parts of what is in reality a continuous tube, is very much in fluenced by the condition of the tube itself. In the normal state, the colour of the tubes often contrasts with that of' the matrix, which when free from blood is of a whitish colour, so that the tubes are visible through the sub stance of the matrix, and the observer can trace the continuity of the tube between the different meshes of the tissue. The same observation applies to the tubes when filled with blood ; in some parts of the specimen portions of the tube appear quite isolated, where they are concealed by the overlying matrix (fig. 150, a a), while in other parts the tubes are more or less distinctly visible through the intervening fibrous tissue (b b). In some parts transverse sections of the tubes are seen, and in other instances a considerable length of tube appears, uncovered by matrix ; this tissue having been removed by the knife, while the tube itself has just escaped the section. In a subsequent part of this article reference will be made to certain pathologicar changes, as a consequence of which the tubes lose their epithelial lining and become more or less transparent ; and in this condition, when they are packed in the meshes of the fibrous tissue, they have somewhat the appearance of sepa rate globular or oval cells, and they have ac tually been described as such by an expe rienced microscopical observer.* This ques
tion will be fully considered hereafter, the object of the present brief allusion to it being to show the importance of studying the ar rangement of a tissue which gives peculiar appearances to the parts with which it is con The large oval space represented in fig.149, c, indicates the position of a Malpighian body ; these bodies, as well as the tubes, being accu rately fitted into meshes of the fibrous ma trix. The arrangement of the fibrous tissue in the medullary cones is somewhat different from that of the cortical portion. The tissue in this part is more abundant, so that the tubes are separated by it to a greater distance than in the cortical portion of the kidney. The hardness and greater cohesion of the tissue of the medullary cones, as compared with that of the cortical portion, is in great part due to the more abundant fibrous matrix in which the tubes of this part are packed. A transverse section of the cones shows the matrix in the form of circular meshes sur rounding the tubes, as in the cortical portion ; but on a longitudinal section the meshes ap pear elongated, thus corresponding in form with the venous capillary meshes which oc cupy the substance of the fibrous tissue, and which in this part of the kidney are elongated in the direction of the tubes. There being no Malpighian bodies in the medullary cones, the larger meshes of the matrix which contain these bodies are not present in this part of the kidney. In order to ascertain the relation which the blood-vessels bear to the matrix, it is necessary to examine portions of a kidney which has been artificially injected, or one in which the vessels are filled with blood. It will then be seen, that while the tubes (fig. 151) accurately fill the meshes of the fibrous tissue, the capillary vessels (b b and c), form ing a plexus which surrounds the tubes, are contained in the substance of the same tissue (c c). When the blood-vessels are empty, they cannot be distinguished from the fibrous tissue in which they are imbedded; it is only by the contrast of their colour when filled with blood, or with injection, that it can be ascertained that, in addition to the capil lary vessels which surround the tubes, there is a connecting fibrous tissue, the office of which appears to be to support and retain in position the various complicated parts — tubes, Malpighian bodies, and blood-vessels — amongst which it is placed.* Tubuli Uriniferi.— The tubuli uriniferi are so intimately connected with the Malpighian bodies, that it is not possible to give a com plete description of one of these structures without an occasional reference to the other.