This book reviews the long-standing debate over the relative merits of a high-protein versus a low-protein diet. When protein (or 'animal substance') was first discovered in vegetable foods it was hailed as the only true nutritional principle. Leibig, the leading German chemist of the mid-nineteenth century, believed that it provided the sole source of energy for muscular contraction. In contrast, health reformers argued that high intakes were over-stimulating, leading to dissipation and decline. The subject came to widespread public attention again in the 1950s as the United Nations debated the need for providing protein supplements to Third World infants. At a time when the concern has resurfaced that over-consumption of protein in affluent societies may damage health, this book provides a fascinating historical perspective.