Of the various theories of Bright's disease, those seem the most rational which regard the process or processes as primarily nutritional disturbances, with secondary structural involvement of different organs. The first important structural derangement is probably endarteritis, with later involvement of the kidneys. We are not at present concerned with the various lesions, nor with the etiological factors, leading to the disorder. In this view of the matter, it becomes important to know the earliest phenomenon which can be relied upon to indicate the presence or approach of these very serious lesions. The general symptoms, headache, vertigo, neuralgic pains, dyspnœa, anæmia, etc., are too indefinite for practical application. The appearance of albumin and casts in the urine occurs too late for the purpose, and albuminuria alone is altogether too uncertain a sign to be of much importance.
It has long been known that the daily excretion of urea is