In the course of our investigations (1, 2) and following the studies of others (3) of the lipids in the blood of nonimmunized and immunized horses, an investigation was made of the composition of the alcohol-ether extract of serum prepared according to the method of Bloor (4).
Four-cubic-centimeter samples of sera were made up to 100 cc. with redistilled 95-per-cent alcohol and ether, 3:1. Total and free cholesterol were determined by precipitation with digitonin, according to the methods of Osato and Heki (5). Forty cubic centimeters of the alcohol-ether extract of the serum were used for the determination of total cholesterol and 125 cc. for the free cholesterol.
The estimation of phospholipids was based on the determination of phosphorus and calculated as lecithin, molecular weight 778. Fifty cubic centimeters of the alcohol-ether extract of the serum and 1.25 cc. of saturated magnesium nitrate solution were evaporated to dryness in a 50-cc.