426 Dr. John Mailers Examination of [June 



rythmus of the contraction of this organ is peculiar, being 

 neither synchronous with the heart nor respiration, nor with 

 each other, and can be readily perceived when viewed pos- 

 teriorly through the skin, and very distinctly when the skin 

 is removed . Under this organ lie a large vein and artery, 

 whose circulation, however, has no influence upon the 

 organ. The organ itself is oblong, and contains a clear 

 colourless liquid, which flows out when an incision is made ; 

 and if we inflate it downwards, not only are the vessels of 

 the thigh and leg filled, but likewise some of those of the 

 trunk. When inflation is made upwards a lymphatic duct 

 leading to the back is filled. It may be remarked, that by 

 inflating the organ, the whole veinous system, as well as 

 the lymph vessels, are filled with air, which would go to 

 demonstrate the existence of an intimate connexion between 

 these two sets of vessels. The same lymphatic apparatus 

 was detected in the toad, similarly situated as in the frog, 

 and in the salamander and green lizard, on the side at the 

 root of the tail, close behind the extremity of the rectum. 

 Dr. Marshall Hall has described a peculiar structure situ- 

 ated near the tail of the eel, which serves as an auxiliary to 

 the heart, and performs a regular diastole and systole, 

 quite distinct from that organ. Miiller, aware of this dis- 

 covery, examined the eel, and found, at the point of the 

 tail, a pulsating organ containing a transparent reddish 

 liquid, which was carried forward into a canal lying on the 

 inferior side of the tail. On injecting the organ a number 

 of large vessels were filled with the mercury on the same 

 side on which the incision for introducing the injecting 

 liquid was made. The soft fins were likewise reached by 

 the mercury, and their rays presented the appearance of 

 parallel canals. A principal canal 1| line in diameter, cor- 

 responding with one on the upper side, lies on each side of 

 the inferior surface, at the insertion of the fins, and between 

 them are numerous small longitudinal vessels and transverse 

 branches. Each of the vessels connected with these organs 

 must be injected from their own side, either through the 

 organs or by the longitudinal canals. 



About the end of the gut the lateral canals on the under 

 side appear to communicate on both sides with each other. 

 The organ itself is obviously double, for pulsation is observed 



