EXPERIMENTS WITH SERUM

1. Serum exerts an augmenting action on the heart in that it increases contraction‐height and improves tone, with culmination in systolic arrest. 2. Lipoids (cholesterol and lecithin) exert two independent actions on the heart: (1) A depression due to interference with Ca function. (2) An augmentation due to colloidal changes. At low concentrations augmentation predominates. At high concentrations depression predominates. 3. The “alcoholic extract” of serum exerts the same actions as lipoids. 4. Since serum is solely augmentor and its alcoholic extract exerts a new independent action of depression, the depressor constituents (lipoids) of this extract could not have been present in the serum in the form they are present in the extract. 5. The term alcoholic extract of serum is a misnomer, because the constituents of this extract exert an action which is not exerted by serum. The alcohol first breaks down serum, and the alcoholic extract consists of break‐down products soluble in alcohol. We cannot deduce the functions of these substances in serum from the actions of the pefused alcoholic extract. We only know they are different.