The lymphagogue effect of extract of lobster muscle, which is one of the first class of HEIDENHAIN'S lymphagogues, is essentially the action of adenine nucleotides liberated from the tissues by the injection of this extract. And also it is proven that these nucleotides are liberated in a larger quantity from organs in other parts of the body rather than from viscera. This conclusion is based on the following evidences. 1) Systemic-venous injection of the extract accelerate the outflow of a uncoagulable, highly proteinized lymph from the thoracic duct of dog, accompanied by a fall in arterial blood pressure and a rise in portal pressure. All these phenomena are also observable by the intravenous injection of adenosine triphosphate (ATP). 2) Repeated injections weaken the reactions to this extract (Tachyphylaxis). 3) Immediately after vascular administration of the extract adenine nucleotides including ATP are detected in blood plasma spectrophotometrically as well as paperchromatographically. Quantitatively the content in nucleotides is higher in the plasma from the femoral vein after systemic-venous injection than from the hepatic vein after portal injection. 4) No definite increase of histamine in blood can be recognized after systemic-venous injection of the extract.