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Urinary excretion patterns of adult male Wistar rats exposed for 11 weeks to control (25°C) or to adverse conditions (5°C, 35°C), or simulated altitude (equivalent to 18,000 ft.) were determined using 24-hour fasting urine specimens collected weekly during the final 4 weeks. Relative to metabolic body weight (kg3/4), fasting water intake tended to vary directly with temperature, but urinary sodium, potassium, magnesium, calcium, phosphate, urea, valine and alanine tended to vary inversely with temperature. Creatinine, uric acid, histidine, glycine, serine, methionine, glutamic acid and aspartic acid excretion tended to vary nonlinearly with temperature. Altitude induced reductions in the majority of the urinary constituents.

A comparison was made of the morphological effects of cold, heat and simulated altitude on adult male rats given exposures of 24 weeks' duration. By the use of covariance analysis it was possible to determine the extent to which organ weights were dependent upon body weight and to adjust the values in order to remove body weight influences. For liver, heart and kidney, adjusted weights indicated temperature-dependency, while pressure-dependency was established for liver and kidney only. Histologically, temperature-dependency was indicated for liver, kidney, thyroid, adrenal and pituitary. Fur weight was reduced in heat but not altered in cold. Fasting in cold induced changes in adrenal and thymus weight and unusually high body weight loss; in heat, fasting caused a significant thymus weight loss without adrenal weight increase. The thymus-adrenal ratio was elevated during a 24-hour fast in all environments except cold, where it was decreased.