The Constitution of Protoplasm

Abstract

Normal and tumor cells were mechanically fractionated by differential centrifugation. Purified fractions were obtained from nuclei and cytoplasm, including secretory granules, and small particles provisionally called microsomes. Their origins, nature and properties were detd. Secretory granules and microsomes are chem. similar, suggesting related origins. Mitochondria may largely represent mature sec. granules. Microsomes and sec. granules were found to contain ribonucleic acid. These cytoplasmic components, like other nucleic acid-containing structures, may be endowed with the property of self-duplication.