XXVIII. The caudal heart of the eel a lymphatic heart.—Effect of the force with which the lymph-stream is propelled therefrom on the flow of the blood in the vein into which the heart opens.— Explanation of the appearance of blood propelled in successive drops, as if from the heart, along the caudal vein.—Influence which the force of the lymph-stream from

Abstract

The remarkable pulsating organ in the tail of the eel, which forms the subject of this paper, was discovered by the late Dr. Marshall Hall. He viewed it as belonging to the blood-vascular system, and named it the “Caudal Heart." His description of it was founded on observations made on small eels under the micro­scope. In large eels the heart may, as he also pointed out, be seen with the naked eye by spreading the tail on a plate of glass and viewing it against the light. Not only, however, are the pulsations of the organ itself thus visible, but also the very peculiar appearance of successive drops of blood propelled, as if from the heart, with great velo­city along the caudal vein, which was observed by Dr. Marshall Hall in his microsco­pical examinations, though incorrectly interpreted by him: To explain the true nature of the phenomenon here referred to,—to prove thereby that the caudal heart belongs, not to the blood-vascular system, but to the lymphatic system, and to inquire into the influence which the force of the lymph-stream from the heart exerts in accelerating and promoting the flow of blood in the caudal vein, constitute the object of the communication here presented to the Royal Society.