The test diet is a mixed diet containing known amounts of water, nitrogen, and chloride, together with the food diuretics (purins, salt, and water), as can be seen. The diet is divided into unequal portions containing known but varying amounts of fluid, nitrogen, and salt. Two-hour specimens are collected from 7 A.M. to 9 P.M., and one night specimen is obtained containing all the urine passed between 9 P.M. and 7 A.M. Each specimen is analyzed for volume, specific gravity, total nitrogen, nitrogen concentration, total chloride, and chloride concentration. ~Purpose of Tests.~--The purpose of the test is to find out to what extent and in what manner the diseased kidney under stimulation by the various diuretics taken in the food reacts in putting out the varying amounts of salt. Dr. O'Hara likewise describes another test known as ~The Added Urea and Salt Test~, which was first described by von Monakow and also carried out in the Peter Bent Brigham Hospital. The method used was as follows: ADDED UREA AND SALT TEST Patient is given 75 grams of protein, 4 grams of sodium chloride, and 1500 c.c. of water, with a caloric value of from 2000 to 2200 calories. After the output of fluid, salt and nitrogen reaches an equilibrium on this diet on one day 10 grams of additional salt is given and several days later the patient receives 20 grams of urea. This order may be reversed. The daily output of urine, salt, and nitrogen is determined and charted. After the salt and nitrogen is added to the diet in normal individuals, their excretion after forty-eight hours returns to its previous level. In diseased kidneys this may not be the case. ~Value of Tests.~--Thus it is seen that in these tests for kidney functions, an effort is made to determine the extent of damage wrought by the disease upon the renal organs and the manner in which they react under definite circumstances. However, it is not so simple as it would seem to formulate a dietary based on the findings resulting from the renal tests. Notwithstanding this, these tests are coming more and more into use, both in hospitals and private practice, and a nurse must understand just how they are carried out, and must realize that unless her part is performed with absolute accuracy the entire value of the test will be obliterated. Too much stress cannot be laid upon this phase of the test, if it is to be of any value whatsoever in determining the condition of a diseased kidney. CHRONIC INTERSTITIAL NEPHRITIS