This is an extremely interesting synthesis of some of the investigations of the workers in the "fatigue laboratory" of Harvard University. The physiologic adaptations of man to great heat and high altitudes are presented in detail and are contrasted to the biologic adaptations of animal species either native to or successfully introduced into such regions. The modern views of energy exchange serve as an introduction and background to the main portion of the book. The central idea that adaptability depends on the success of the circulatory and respiratory systems in supplying oxygen to the tissues is illustrated by the maximal abilities of the organism, as displayed by trained athletes. Their finest subject in this respect was able to deliver to his tissues 5.35 liters of oxygen per minute at a cardiac output of 35 liters per minute !
Studies in the desert demonstrated that successful adaptation consists in: (1) the ability