Natural products rarely exist in a state of maxi-mum purity or maximum concentration. They are generally found in plant or animal tissues or fluids in the presence of other natural products, and often in small amounts, or in inactive physical states in which they are stored as biological reserves. Natural function may demand the liberation of the active component in but a small, con-stant concentration. The greatest value of each active component, however, whether as reagent in therapy or in chemical technology, is often in a highly purified, stable and concentrated state. The present series of reports describes the de-velopment of a system for the separation of the protein and lipid components of a biological tissue, first into a small number of fractions in which the major components are separated, and then into a large number of subfractions into which they are further concentrated and purified. The tissue that has thus far been most thoroughly investi-gated is human blood. The methods that have been employed are, however, general and can be applied to give comparable inclusive fractiona-tions of other biological systems in theinterest of obtaining as many as possible of their valuable (la) This work wr. s originally supported by grants from r. he Rockefeller Foundation and from funds of Harvard University. It was aided early in 1941 by grants from the Committee on Medicine of the National Research Council, which included a grant from the American College of Physicians. Since August, 1941, it has been carried out under contract, recommended by the Committee on Medical Research, between the Office of Scientific Research and Development and HarvardUniversity.(lb) This paper is Number 43 in the series “Studies on Plasma Proteins’’from the Harvard Medical School, Boston, Massachusetts, on products developed by the Department of Physical Chemistry from blood collected by the American Red Cross. We are indebted to the Antitoxin and Vaccine Laboratory, Massachusetts Depart-ment ofPublic Health, for preparing in sterile and safe form the various fractions that have been made available for clinical use; are now licensed products under the National Institute of Health and have been prepared in large amounts in industrialplants under contract with the United States Navy which, for nearly five years, has collaborated in this program.(lc) This article has been released forpublication by the Division of Publications of the Bureau of Medicine and Surgery of the United States Navy. The opinions and views set forth in this article are those of the writers and are not to be considered as reflecting the policies of the Navy Department.(ld) Our various chemical and clinical collaborators in this and other institutions are making their results available in this and other journals. We would like to acknowledge their assistance in the solution ofmany problems as well as that of members ofthe staff of the Pilot Plant which has been in continuous operation for the past four and one half years and included, besides the authors, R. Ambrose, M. J. E. Budka, J. H. Cameron,. Y. Clark,. E. Collier, C. Goodrum,. T. Gordon, PM Gross,. M. Hasson, RW Kelty, LH Larsen, S. G. Miller, DA Richert,. H. Smith, AH Sparrow, and J. H. Weare.(le) Lieutenant H (S) USNR. components as nearly as possible in their natural state.

The separation of the many protein and lipid components of a biological fluid or tissue can be accomplished by control of their relative solu-bilities in a multi-variable system. The larger the number of components and the more nearly alike their physical chemical properties, the more variables, each under accurate control, may be needed in order to determine conditions in …