The samples of foods and feces received from Springfield at the Nutrition Laboratory in the quart glass jars were first carefully weighed and checked, then transferred to previously weighed white enamel pans, and dried to approximately constant weight. To accomplish the drying of the large number of food samples, which were somewhat larger than the usual samples dried, also the large number of feces, required a specially constructed oven. This oven, which is shown in detail in figure 1, consists of an asbestos-walled cabinet with doors that open in front and stout wire-gauze shelves. At the top, through an 8-inch furnace pipe, air was thrown out by means of an electric fan placed in the pipe. At the bottom of the chamber an 8-inch furnace pipe led air from the room into the oven; the air was heated by means of a large gas burner of rose pattern. By regulating the speed of the electric fan and the flow of gas, the temperature could be kept at approximately 70° C. the entire time. Throughout the whole period of 4 months, there was rarely difficulty with the temperature control. As fast as the foods were partially dried, they were stirred, a fresh surface was exposed, and the samples were moved about in the oven so as to take advantage of the greatest heat and the greatest volume of air.

When the samples were thoroughly dried so as to be in condition for grinding, they were allowed to reach room temperature and stand in the room for 24 hours or more. They were then weighed, put through a hand mill or meat chopper one or more times, and finally bottled either in the regular glass jars or in smaller glass jars, with stoppers, ready for analysis. At this stage the recorded weights of the dried samples, a and b, could be compared and notation made of marked discrepancies, if any existed. Theoretically both samples should have dried to essentially the same weight.

Fig. 1. - Drying oven.

The walls and doors of this oven are of asbestos board and the shelves are of strong wire mesh. a rose burner in the air intake at the bottom furnishes the heat; the temperature of the oven is indicated by a thermometer at the side. Ventilation is secured by a fan placed in the exit pipe above the oven.

Methods Of Analysis. Urine

Observations on the urine were confined to the crude observations of specific gravity with a standard spindle and to the exact determination of nitrogen by the Kjeldahl process. The Laboratory is well supplied with automatic pipettes, digestive apparatus, and stills for the most rapid work. The 1,000 or more urine analyses involved in this research were made exclusively under the supervision of Miss Elizabeth B. Babcock, and were carried out with extraordinary fidelity, rapidity, and accuracy. In this work she was assisted by Miss Marion L. Baker and Mr. Harry Silverman.