In a recent number of the Archives of Internal Medicine1 appeared a paper by T. Addis and Marjorie G. Foster under a title identical with the one given to this communication, wherein were offered experimental data which seemed to them to lead to the following conclusions:
The specific gravity of the urine of normal persons was measured under varying conditions designed to place a strain on the concentrating activity of the kidney. It was found that not even an approximate idea of the work of the kidney in the excretions of solids could be obtained from the results. It is therefore concluded that specific gravity determinations cannot form part of any method intended to measure the amount of secreting tissue in the kidney.
Although it appeared to us evident that the data as presented had been wrongly interpreted, we appreciated the possibility of correct conclusions in spite of false premises