Facing the problem of kidney function, we are accustomed to consider mainly the purely excretory function in the strictest sense of the word; that is the passing over of a definite substance from one side of the kidney filtrum, from the blood, to the other side, the urine. This is equally true in health and in disease, and it forms the basis for most of the work hitherto carried out.
It must be remembered, however, that the kidney is not only a filtration apparatus but it acts also as a delicate chemical laboratory. Schmiedeberg,1 in 1876, discovered the synthesis of hippuric acid from glycocoll and benzoic acid as a function of the kidney. According to the present day conception, this synthesis is not localized exclusively in this organ. It is interesting to note that this process as a kidney function test has recently been drawn into the field of