connection with the medial change. A few of the arteries have their lumen completely obliterated. This is meant to illustrate the picture of vascular disease in the kidney in the absence of satisfactory evidence that nephritis _per se_ antedated or accompanied changes in the vessels. In such cases vascular disease dominates, renal parenchymatous damage being relatively inconspicuous. Two old carnivores, a paradoxure and a skunk, presented shrunken kidneys with prominent wide-walled vessels but in these some definite evidence of old nephritis was at hand. In so far as the relation of senility to nephritis is concerned the data at hand are not conclusive. In many old animals some degree of fibrosis is present without the existence of truly destructive changes in the parenchyma. Plimmer of London writes that there is increased nephritis in old age but from our material I would be inclined to put in that in many cases the nephritis was the reason for old age rather than that old age brought on a nephritis. However the exact length of life and of captivity is known in too few specimens to make a conclusion justified. ASCENDING NEPHRITIS. There is some difference of opinion as to the definition of the term ascending nephritis, a confusion arising partly from the intended meaning of the participial adjective, partly from the frequency with which infections or obstructions of the urinary outlets antedate or accompany suppurative nephritis. Perhaps our records may help to straighten out this matter. Ascending nephritis means for our study an infection which passes from the pelvic surfaces of the pyramids outward toward the renal capsule. Thus it is immaterial whether there be or be not an obstruction lower down. Such forms of nephritis are infiltrative, frequently purulent and are dependent upon pyelitis or the settling of bacteria in the deepest parts of the medulla.