At the age of thirteen, chemistry enthusiast Justus von Liebig (1803-73) witnessed the devastation caused by a summer of crop failure. Three decades later, Liebig had become a leading German chemist based at the University of Giessen and had made significant contributions to agriculture and medicine in addition to his pioneering work in organic chemistry. This 1842 study in animal metabolism includes detailed analysis of the chemical transformation undergone in healthy and diseased organisms. Although Liebig considers that chemical analysis alone is not sufficient to explain physiological processes driven by 'vital forces', he argues that it offers quantitative research methods that are superior to mere observation. Several of his works, including this one, were translated into English by his colleague, Scottish chemist William Gregory (1803-58). Liebig's laboratory-based teaching methods quickly gained popularity among British researchers and contributed to the founding of the Royal College of Chemistry in 1845.