Elementary Analysis and the Origins of Physiological Chemistry

IN 1842 the great organic chemist Justus Liebig declared in his famous Animal Chemistry that every physical and mental action of an animal is the result of chemical changes occurring within its structure or substance.l The data and the ideas which he presented in support of his claim opened a new era of intensive exploration of the chemical aspects of biological processes.2 Yet Liebig's work also represents the culmination of efforts which had lasted for over fifty years. It was the most ambitious and comprehensive of a long series of attempts to deduce phenomena occurring within living organisms from the results of the chemical analysis of organic compounds. Between 1780 and 1840 the belief that chemical reactions underlie bio-