The DIAGNOSIS of a calculus remaining in the pelvis of the kidney depends chiefly on the determination of hæmaturia and pyelitis for which no other cause can be found, and upon the presence of pain in one loin. It is naturally greatly assisted by the presence or history of renal colic. An aching pain in the loins, more or less permanent, is a frequent but not invariable symptom. It may be such as to prevent the patient from standing upright, and cause him to assume an habitually stooping posture in standing or walking. A careful examination of the urine in conjunction with this symptom, especially if an unusually abnormal condition has been preceded by an exacerbation of the pain, may make the diagnosis almost certain. In the beginning of a case occasional not severe hæmaturia, with some increase of mucus or a little pus, may be all that can lead to the suspicion of calculus as the cause of pain. At a later period an increase of these symptoms, with a considerable quantity of the peculiar irregular epithelium lining the pelvis, may be observed. The latter constituent, however, can hardly be looked upon as entirely conclusive of pyelitis, since the lower urinary passages may give rise to cells of about the same form and size, and the irregularity is likely to be increased beyond recognition by the presence of inflammation. They may also undergo change of form in the urine. The presence of transparent or other casts denotes the irritation of the renal parenchyma. The point of chief difficulty in the diagnosis of pyelitis is the determination of the origin of the pus, whether from the kidney or the bladder. Cystitis may be only partly excluded by the absence of dysuria. A point of considerable weight is the reaction of the urine, that from the kidneys being usually acid, while that from the bladder, when cystitis of much severity exists, is alkaline or rapidly becomes so. The pus coming from the kidneys is more intimately mixed with the often profuse urine than when formed in the bladder. The whole of it does not in the former case completely subside, but remains in sufficient quantity to form a turbid or opalescent mixture--the polyuric trouble of Felix Guyon, according to whom this condition in an acid urine is strongly indicative of renal as distinguished from vesical lesion. In cystitis the pus subsides in more or less distinct masses, but if the urine is alkaline, or when it becomes so, is altered to a ropy consistency usually spoken of as muco-purulent.