The study by Vincent P. Doile investigates the relationship between non-esterified fatty acids (NEFA) in plasma and glucose metabolism. The concentration of NEFA in plasma increases after heparin injection, likely due to the hydrolysis of neutral fat in chylomicrons by released lipase. However, the concentration of NEFA does not increase during spontaneous clearing of alimentary lipemia, contrary to expectations. Feeding glucose or injecting insulin causes a significant decrease in NEFA concentration, while injecting epinephrine leads to a marked rise. A new method for measuring NEFA is described, which is rapid, simple, and sensitive. The method involves extracting lipids into a one-phase system and converting it to a two-phase system using heptane and isopropyl alcohol. The titratable acidity of the heptane phase is then measured, providing a reliable quantification of NEFA. The results show that NEFA levels rise during fasting and decrease after a mixed meal, oral glucose, or injected insulin. Corn oil, even when causing lipemia, does not affect NEFA levels. Insulin and glucose have similar effects, with glucose causing a more pronounced decrease in NEFA. Epinephrine, on the other hand, significantly increases NEFA levels. The study confirms that NEFA levels are influenced by fasting, meal composition, and hormonal factors, but not by dietary fat alone. The new method for NEFA determination is more efficient than previous techniques.The study by Vincent P. Doile investigates the relationship between non-esterified fatty acids (NEFA) in plasma and glucose metabolism. The concentration of NEFA in plasma increases after heparin injection, likely due to the hydrolysis of neutral fat in chylomicrons by released lipase. However, the concentration of NEFA does not increase during spontaneous clearing of alimentary lipemia, contrary to expectations. Feeding glucose or injecting insulin causes a significant decrease in NEFA concentration, while injecting epinephrine leads to a marked rise. A new method for measuring NEFA is described, which is rapid, simple, and sensitive. The method involves extracting lipids into a one-phase system and converting it to a two-phase system using heptane and isopropyl alcohol. The titratable acidity of the heptane phase is then measured, providing a reliable quantification of NEFA. The results show that NEFA levels rise during fasting and decrease after a mixed meal, oral glucose, or injected insulin. Corn oil, even when causing lipemia, does not affect NEFA levels. Insulin and glucose have similar effects, with glucose causing a more pronounced decrease in NEFA. Epinephrine, on the other hand, significantly increases NEFA levels. The study confirms that NEFA levels are influenced by fasting, meal composition, and hormonal factors, but not by dietary fat alone. The new method for NEFA determination is more efficient than previous techniques.