THE EFFECT OF INTRAVENOUS ACETYLCHOLINE INJECTIONS ON THE THORACIC LYMPH PRODUCTION

Abstract

1. Intravenous injection of acetylcholine in doses 0·02–0·2 γ/cat and 0·2–2 γ/dog causes an increase in the lymph‐flow through the thoracic duct.2. Experiments are described proving that most of the increased lymph‐flow comes from the intestines, and a smaller proportion from the liver.3. It was shown by direct microscopical observation that acetylcholine causes a dilatation of both the precapillary arteries and the capillaries of the villi, but the dilatation of the former is greater. Such a condition results in an increased lymph production. The action of acetylcholine on the capillaries and precapillary arteries is regarded as the cause of the increased lymph‐flow. Atropine annuls the effect of acetylcholine on the lymph‐flow. The effect of atropine on the blood pressure and lymph‐flow is parallel. The effect of acetylcholine on the contractile elements of the vascular system is probably not the sole cause of the increased lymph‐flow because in animals dyed with chlorazol skyblue the increase in the lymph‐flow is greater, although the capillary changes are less marked. It seems probable that acetylcholine also increases the permeability of the capillary walls.4. It has been shown that contraction of the villi also provoked by acetylcholine cannot be the cause of the increased lymph‐flow, because chlorazol skyblue, while completely paralysing the motion of the villi, enhances the effect of acetylcholine on the lymph‐flow. Based on this fact the supposition that the contraction of villi plays any important rôle in the emptying of the contents of the villi and the propulsion of lymph is questioned. It had also been shown that increased peristalis cannot be the cause of the increased lymph‐flow, though both factors may play a rôle in the propulsion of the lymph. Gland activity as a possible cause has also been excluded.5. Since acetylcholine exerts its influence on the lymph‐flow in physiologically occurring doses, and since its effect is evanescent and repeatable many times, acetylcholine is regarded as a compound acting as a physiological lymph producer.The author has pleasure in thanking Professor Sándor Belák for his many useful suggestions in the course of this work.