EVALUATION OF ANTIPERSPIRANT ACTIVITV 761 The temperature controller (Fig. 9) senses the temperature in the air duct rather than in the chamber and is set for a temperature higher than that actually applied to the subject. However, it is calibrated to pro- duce the desired exposure temperatures, which are read on an auxiliary thermometer. The rapid eyeling of the heater that results from this arrangement maintains extremely stable exposure temperatures The level of temperature to which each subject is exposed depends Figure 11. Phosphorous pentoxide cell upon his particular nature and to outside relative humidity. Each in- dividual has a different and critical temperature-humidity ratio above which active perspiration ensues. The relative humidity tends to re- main fairly stable during tests thus the critical temperature of the sub- ject is of greater concern and is determined at the start of a test for each. During a test the subject is heated to his critical temperature or slightly below. His perspiration is then brought about by having him work his legs as if riding a bicycle. To decrease the perspiration he is allowed to

762 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 12. x-y recorder rest. In this way, the variation in perspiration will cause the x-y re- corder to trace a sloped pattern on the graph. It has been found that when a subject lies still in the warm atmos- phere he may be lulled to sleep by the hypnotic drone of the equip- ment. When asleep, his perspiration can become quite erratic. An actual alternating pulse of one axilla followed by the other has been ob- served. The moisture monitors (Fig. 10) are placed side by side so that their meters may be viewed simultaneously. The two flow meters on the top right of each instrument measure the total flow of gas and the quantity that is sampled for moisture content. The system is calibrated to read in •1/1 (parts per million) of moisture u-'hen the sample flow is set for 10 ml/min. Since the measurements required are all relative, the exactness of this calibration is unimportant. However, the gas flows should not change during a test. Several scales may be selected by the attenuator switch on the left front of each instrument. Its position will depend on the relative output of perspiration of the subject under test.