STUDIES ON THE FORMATION OF COLLAGEN I. PROP~TmS AND FRACTIONATION Or NEUTRAL SALT EXTRACTS Or NORMAL

The discovery of a form of collagen which can be extracted from fresh connective tissue in cold, neutral, and mildly aklaline media (1-5) has suggested that a fraction of the total collagen exists in a dispersed or loosely aggregated state in the extracellular, extrafibrillar matrix of the connective tissues. The process whereby a dispersion of collagen molecules (tropocollagen (6)) might be polymerized in the tissues was suggested by the observation that simple warming of the extract to physiological temperatures results in the precipitation of fibrils with the typical detailed fine structure of native collagen (4, 5). In addition to describing a new procedure for isolating and purifying the extracted collagen, this paper presents some results of an exploration of the properties of crude neutral salt extracts of fresh guinea pig corium as a base line for further studies on the role of the extracted components in the fibrogenesis of collagen and the physiology of connective tissues.