This classic of biochemistry offered the first detailed exposition of the theory that living tissue was preceded upon Earth by a long and gradual evolution of nitrogen and carbon compounds. Contents: 1. Theories of Spontaneous Generation of Life. 2. Theories of the Continuity of Life. 3. Theories of the Origin of Life at Some Distant Period of the Earth's Existence. 4. Primary Forms of Carbon and Nitrogen Compound. 5. Origin of Organic Substances. Primary Proteins. 6. The Origin of Primary Colloidal Systems. 7. Origin of Primary Organisms. 8 Further Evolution of Primary Organisms. 9. Conclusion. Bibliography. Index of Names. Index of Subjects. Unabridged republication of the 1938 edition.