Where obstruction was more definite the following cases were observed. Suppurative nephritis succeeded upon gangrenous cystitis after uterine prolapse in a deer. The following cases of pyelitis and nephritis were associated with calculus, only in the renal pelvis—an armadillo, Tasmanian devil, a deer and a goose. A cockatoo had a stone in the cloaca which seemed to cause a definite obstruction to both ureters and a catarrhal inflammation of the wall. Pyelitis and interstitial nephritis can also follow excessive urate collections in birds. At a later time this will be discussed more fully, but at this place two cases of distinct abscess formation in a renal lobule based upon urate collections may be mentioned since in a measure the lesions were dependent upon obstruction. It is therefore evident that all the theories of the causation of pyelitis with resultant nephritis seem acceptable. It has been claimed that bacteria may be found in the blood stream before evidences of pyelitis present themselves. Concerning this our records offer no information, but it is worthy of note that five of twenty-one instances gave a picture of septicemia. It is, however, fair to state that, while mild cases of pyelitis occurred where there was, judging from the protocol and histological sections, obvious opportunity for its ascent, in ten other cases of cystitis and urethritis no pelvic or renal disease is recorded; two of these were acute exudative cystitis and one was a tumor. It seems that wild animals seldom live long enough to have obstructions exert back pressure of urine to the extent which one is accustomed to see in human medicine. Hydroureter and hydronephrosis have not been seen. Abscess of the kidney has occurred occasionally in the metastatic form and only twice as the large destructive process such as is seen in the human being (surgical kidney). One massive abscess was seen involving about one-third of the organ, and this seems to have had a tuberculous basis. Another destructive purulent nephritis was quoted on page 268 when illustrating compensatory hypertrophy. Examination of records and preserved specimens of nephritis reveals few striking differences which might be considered characteristic for the various orders. This is possibly due to the fact that the lesions have been classified under the same system, a method which has proven convenient and consistent. In support of this one might refer to that form of nephritis which gives the most definite clinical and pathological picture of renal disease, namely the chronic parenchymatous. This is fairly well represented in Primates, Carnivora and Ungulata. In one-fourth of the cases one finds distinct edema, especially in the body cavities, cervical and mediastinal tissues, and in one-fifth an appreciable grade of anemia; uremia was the terminal picture in one animal of each order. HISTOLOGY OF NEPHRITIS.