The Influence of Ultra-violet Rays on the Body Weight

Abstract

THE experiments reported in this paper are meant to be a contribution to the problem of general ray-reaction, the results of which appear to have a theoretical interest as well as a practical one. Methods A total of 141 white mice were used, all of the male sex. There were two series: Series A was abundantly nourished, being fed 32 gm. bread per week—i.e., 8 gm. each Monday and Wednesday and 16 gm. on Friday. Series B was scantily nourished, being fed 16 gm. bread per week—i.e., 4 gm. each Monday and Wednesday and 8 gm. on Friday. Water was supplied to both series ad libitum. In Series A, 45 mice were radiated while 34 served as controls. In Series B, 32 mice were irradiated while 34 served as controls. The radiation took place daily except Thursday and Sunday. As a light source we used the mercury vapor lamp, type S 500 (Hanauer Quarzlampengesellschaft), with the reflector pushed forward. The radiation time varied from five to eight minutes; the distance was 40 centimeters. The mice were kept in a tin box with a wire cover. During radiation the temperature on the bottom of the box was about 38° C. Results I. Determination of the Radiation Dosage.—The determination of the radiation dosage was made with the aid of a photoelectric cell (zinc cell). With the aid of this cell (1), comparative measurements were carried out between the lamp Type S 300 and the one of the Type S 500 used here. Unpublished experiments have shown that Type S 300 is equal in its intensity to the older type used in our earlier experiments (2) for the determination of the erythema threshold value. For ten parts of the scale on the electrometer, we found the following time averages with diaphragms of 3.5 mm.: 1. [S 500 in 40 cm. distance reflector forward 11.6 sec. 2. [S 300 in 25 cm. distance reflector back 11.3 sec. Under the above-mentioned conditions these two lamps were, therefore, to be considered as equal in intensity. The required distance was thus determined. For the determination of radiation time, however, it was furthermore necessary to account for the diminution of the radiation through the wire cover. For this purpose we chose three wire covers and fixed them in front of the diaphragms. Then we measured the time for ten parts of the scale of the electrometer, using the lamp S 500 at 40 cm. distance. Table I gives the time averages received. Thus it appears that the wire cover diminishes the intensity by about 50 per cent. Our experience has shown us that with a lamp of the Type S 300 at 25 cm. distance (reflector pushed back) about 100 seconds are sufficient to produce a threshold-erythema of the human skin on the forearm. Now, supposing that the sensibility of the human skin on the inside of the forearm is equal to that of the skin of mice on ears and tail, a dosage of 200 seconds with S 500, under the same conditions as above, should be sufficient to produce such an erythema on mice. However, it appeared that 200 seconds were not enough.