William Holt described in the magazine "al-Siz" the experiments conducted in a London hospital to test the reaction to environment and its effect upon a man.

One of the research doctors put him into a hot-air chamber that made the sweat pour down his face and run down his neck; the temperature in this chamber was the temperature of the desert. Then the doctor switched on an apparatus, and the chamber filled with a hot wind whose speed equaled that of the desert winds, reckoned at ten miles an hour. There are chambers fitted out so that their atmosphere becomes like the atmosphere of Aden or of the forests of Burma, which are marked by high heat and humidity.

These chambers were prepared to test the capacity of the men of the three forces — air, land, and sea — to endure the climate of the regions in which they would be fighting.

All the volunteers for the army and navy — Scots, Englishmen, Welshmen, and Irishmen, bank clerks and former navy men — were tested before joining the fighting forces, to determine the strength and endurance of their bodies in these chambers of varied climate, where they perform tasks similar to those they will perform on the fields of battle, in the presence of doctors who take their pulse and check their breathing; and no one of them is asked to perform a task that the doctor has not himself performed beforehand under the same atmospheric conditions in these chambers.

Every draught these men swallow while they are in the chambers is weighed with complete care, and the sweat is weighed as well; the doctor analyzes the amount of water and salt that each one of them loses. The sweat is collected by a new method: on entering the chamber the volunteer puts on sleeves made of oil-impregnated silk which have the property of collecting the sweat from over the arm.

At the bottom is a rubber vessel for pouring the collected sweat into bottles. It has been found that a man loses 15 "pints" of sweat every four hours, and the volunteer spends from 12 to 18 months under test.

Equipment, too, is tested — whether or not it is fit for use in these climates. The choice of clothing was of great importance, and the results reached will be turned to profit in peacetime. The research doctors cooperated with the cotton research centers in Lancashire, and together they succeeded in producing a kind of fabric made especially for the hot regions: it absorbs sweat easily, and you can wring out a shirt made of the cellulose material if it becomes soaked with sweat — though this light material spares you the need for that operation, since it takes up only a very thin film of water, which evaporates quickly. Likewise its fine weave does not allow the mosquito to bite its wearer, nor does the air pass through it either.