During the past nine months, observations on nephritis have been made in this hospital, with McLean's1 urea index as a test for kidney function. The results have been so helpful for diagnosis and prognosis that the technic employed and certain case protocols are recorded in order to show that the test can be carried out advantageously in a tent hospital with only elementary laboratory facilities.
McLean's directions were followed absolutely. Before each test the patient was given from 150 to 200 c.c. of water, to insure a free flow of urine. One half hour later, in order to start with the bladder empty, he voided. The time of voiding was recorded to within one minute. About thirty-six minutes later, at least 3 c.c. of blood were withdrawn from an arm vein into a dry tube containing a few milligrams of potassium oxalate to prevent clotting. At the end of