On Size and Life by Thomas W. McMahon and John Tyler Bonner (review)

practice. In an illuminating examination of the Hippocratic oath, Kass shows that, if ". . . medicine can withstand the theoretical challenges posed by the new biology, if medicine still is nature served rather than nature mastered, and if medicine tacitly knows things about our nature and our life that our biology cannot support, we are invited to seek for a richer and more adequate biology . . ." (p. 12). Kass's reconstructed biology forces us to reconsider what nature testifies about itself: organisms have hierarchical purposes; the human body induces wonder about human being; the necessity of human finitude "turns out to be the mother of aspiration toward the beautiful, the good, the transcendent" (p. 14). If modern science has been too narrow and constricting in its scope and purpose, so too has modern ethics. Toward a More Natural Science is one of those rare recent books that liberates the scientific, intellectual, and moral imagination to reappropriate all of our Western cultural resources. Liberal education, liberal democracy , the humanities, and indeed the sciences can find few more engaging defenses. Richard P. Vance Department ofPathology Wake Forest University Medical Center Winston-Salem, North Carolina 27103 On Size andLife. By Thomas W. McMahon andJohn Tyler Bonner. New York: W. H. Freeman & Co., 1983. Pp. 255. $27.95. This is both literally and figuratively a beautiful book. The authors have assembled a collection of artistic and appropriate photographs to complement the ideas presented in the text and graphs. Although not overly large, the book is as wide as it is tall, making it look as much at home on a coffee table as on a bookshelf. The major appeal of the book, however, is not in its appearance but in its contents. As implied by the title, the subject of the book is the consequence of size and proportion in biology. This is a fascinating subject where similar concepts can be used to explain such diverse relationships as the length : width ratios in nails, the height : diameter ratios in trees, and the body length : weight ratios in animals. The fascination lies in the ability of these concepts to explain both the reasons for the different sizes and shapes in animals and the consequences of variations in size. This subject has captured the attention of many noted biologists over the centuries, and major contributions to our understanding of size relationships have been made by such famous scientists as Galileo, D'Arcy Thompson, J. B. S. Haldane, J. S. Huxley, M. Kleiber, and A. V. Hill. The book succinctly reviews some of this history. A substantial contribution to our understanding of size relationships in biology has been made by one of the authors, McMahon, with the development of the principle of elastic similarity. This theory explains why large animals and trees are relatively stouter than small animals and trees. The greater mass of the larger organisms would cause more bending of their parts if they were not also thicker. The size relationships predicted by this theory can also be used to prePerspectives in Biology and Medicine, 30, 1 ¦ Autumn 1986 \ 153 diet the metabolic rates in animals. Since the early part of the last century, it has been widely, and incorrectly, believed that metabolic rate was determined by surface area. In 1932, Max Kleiber published data from animals of very different sizes showing that surface area does not predict metabolic rate. His findings did not greatly influence the thinking about metabolic rate because he was unable to offer an alternative theory to account for his findings. McMahon's theory, developed over the last 10—15 years does this very nicely. The theory is explained clearly in the book, but, contrary to my expectations, it does not occupy the major part of the writing. The book is devoted to the much more general topic of size relationships. The authors have chosen many diverse examples to illustrate the principles being elucidated. The effects of scaling and size are probably more completely understood in engineering, where dimensions can be manipulated directly and where the effects of these manipulations can be measured. Many examples from physical engineering are therefore included to explain how changes in dimension affect performance. McMahon is an engineer whose scientific...