Ever since Schlayer and his co-workers elaborated their system of differential renal function testing, much attention has been given to the subject of kidney function tests in nephritis. Clinical requirements demand not only that such a procedure shall be simple and easily available for clinical employment, but that it shall be of demonstrated accuracy; otherwise it may lead to faulty deductions in prognosis and possibly to blunders in diagnosis. However attractive it may appear from the pathologic point of view, to estimate the degree to which the different anatomic elements of the kidney are involved, it would seem that the mixed type of nephritis encountered clinically practically disposes of the attempt to weave fine diagnostic distinctions about the reactions secured by differential function tests. With clinical nephritis of the simplest type, there is enough general structural involvement to make conclusions as to special function involvement hazardous.
Many considerations render the