Plasma Lipids of Normal Men at Different Ages*

The present paper has two objects: first, to ascertain the effect of age, beginning with the third decade, on the plasma lipid content of normal men; second, to ascertain the normal ranges, in adult men, of the different lipid fractions determined by the gasometric methods of Kirk, Page, and Van Slyke (1934). Sub-jecls and Blood Sampling-The subjects were men who by ordinary clinical examination were healthy. They were on unrestricted diets. Blood was drawn before breakfast, and was at once heparinized and centrifuged. The plasma and red cells were carefully separated to avoid the inclusion of platelets and white cells. The lipids of the plasma were immediately extracted with alcohol-ether, and the different lipid fractions were determined by duplicate analyses, as described by Kirk, Page, and Van Slyke (1934). Calculation of Data-To render the results into usual terms, and to facilitate comparison with the results of previous authors, we have, from the directly determined values of lipid carbon, phosphorus, etc., calculated the different plasma lipids in conventional units by the following formulae: