MORBID ANATOMY - ACUTE PRODUCTIVE OR DIFFUSE NEPHRITIS. The kidneys are increased in size, the capsules are not adherent, the surfaces are smooth. The cortical portion is red, or white, or mottled. The mucous membrane of the pelvis is sometimes con gested. Of the tubules in the cortex, in some the epithelium is flat tened, in some there is coagulated matter or casts, in some the epi thelium is swollen, degenerated, or contains globules of fat. In those parts of the cortex where there is a growth of new connective tissue, the tubes may be atrophied. The tubules of the pyramids show but little change except that they may contain casts. In the stroma of the cortex there is a growth of new connective tissue, varying in dif ferent kidneys as to the relative proportion of cells and basement substance. This new tissue in many of the kidneys follows the line of the arteries which run up into the cortex, so that it takes the form of wedges. But in other kidneys the new tissue is diffuse, or in ir regular patches.
Many of the glomeruli show only an increase in the size and 1111111 ber of the cells which cover the capillaries, with some swelling of the capsule cells. But in others there is an extensive new-growth of cap sule cells which compresses the tuft of vessels. This growth of new cells from the capsule cells must not be confounded with accumula tions of white blood-cells within the capsules, nor with the growth of new cells on the walls of the capillaries. The glomeruli which are changed in this way are in groups, each group corresponding to some one artery.
The whole picture of the nephritis is that of a combination of exu dative and productive inflammation.
When such a nephritis becomes chronic it is often possible to fol low its course for many years, and to see at the end of that time that the anatomical changes in the kidney are of the same kind, but much more extensive.