Suppuration in the connective tissue between the kidney and its capsule is seen in cattle in low condition, on damp, unimproved soils like undrained river bottoms and estuaries, abounding in acrid and diuretic plants. Even among such animals it is rare and has probably a directly exciting cause in a sprain or blow on the loins, or the presence and movement of a renal calculus. It may extend from suppurations in the substance of the kidney and to such extension the weak or anæmic condition materially contributes. In man, in which such conditions have been more frequently observed, a weak or cachectic condition is considered as an essential accessory factor along with the traumatic lesion (R. Harrison). Similar conditions may be expected to bring about perinephritis in any one of our domestic animals. The author has observed it especially on the low lands on the banks of the Ouse in Yorkshire, England. _Symptoms._ These are mainly those of nephritis in general, shivering, stiff movement in the hind limbs, straddling, frequent passage of urine, straining, difficulty in lying down and rising, tenderness of the loins, dropping when mounted, groaning when turned in a short circle. If the suppuration communicates with the pelvis of the kidney there may be, in females, soiling of the tail, and in males of the prepuce. Blood may be passed with the urine, and pus cells and albumen are found when it is examined. If one kidney only is affected, there is lameness in the corresponding hind limb, the special feature being inability to extend it backward. A swelling on the one side of the loins, and beneath the lumbar transverse processes just posterior to the last rib, is likely to be a marked symptom, and if this persists and is especially prominent at one point, an exploratory incision or puncture will detect the presence of the pus. Fluctuation can rarely be detected, yet in small animals with very flaccid abdomen, the swollen, tender kidney and even fluctuation should be detected at times. The history of the case, the low, damp pasturage, the access to acrid plants, the alimentation with hay or grain covered with cryptogams, the fact of an injury and the low, weak, anæmic condition of the animal should contribute to a satisfactory diagnosis. _Lesions._ In bovine kidneys affected in this way we have found general inflammation and exudation around the entire kidney and inside the capsule, with numerous small abscesses, in many instances communicating with each other. They may extend through the capsule and invade surrounding organs.