An elegant analysis of how animals work and function. Professor Schmidt-Nielsen's incisive account gives a clear understanding of comparative physiology in relation to body size, form and function, energy supply, and environment. The author is concerned with principles. For example, he explains how difficult it may be to lose heat and water from the respiratory tract. This leads to a consideration of the mechanism of panting as a means of heat loss. The author describes the centuries-old problem of how birds breathe, which now has been solved in his laboratory. He then discusses energy...