Determination of small amounts of phosphatides and cholesterol in tissues.

ALTHOUGH there have been many publications on methods of estimating phosphatides and cholesterol in tissue, the value of many of the methods described remains uncertain. In some cases extraction of lipoid substances may be incomplete. Not all of the phosphorus in extracts may be derived from phosphatides. Colorimetric methods of doubtful validity [Nekludov and Chalatov, 1929] are still in use for determining cholesterol. While microgravimetric methods have been worked out for pure cholesterol, they have received little application to tissue-extracts. Before undertaking analyses of tissues we have thought it advisable to make an investigation of methods of analysis. This is reported here with necessary details, together with such results of the analyses as are of methodical interest. An account of analytical methods is necessary to make it possible to assess the value of the analytical data given in an accompanying paper [Jowett, 1931]. Some results of interest in themselves have also been obtained.