6G William F. Allen 



cartilage, open dorso-eeplialad into the caudal vein, the orifice being 

 guarded by a valve. In the ventro-cephalic corner there is a second 

 opening, also guarded b}- a valve, through which the subcutaneous lym- 

 phatic or blood canals empty. According to Greene, the caudal hearts 

 in the hagfish are not of themselves muscular or contractile, but are 

 filled and emptied by a contraction of the musculi cordis caudalis, which 

 lies laterad of the heart and presses it against the median cartilage. 

 These muscles are said to be entirely separated from the heart, and are 

 not to be regarded as part of it. In the hagfish, then, the caudal hearts 

 or sacs receive the blood or lymph from the subcutaneous spaces and 

 drive it into the caudal vein. 



By far the best description of the caudal heart of the eel is given by 

 Jones.^^ From pp. 676-9 and Figs. 1 and 3, the caudal heart is repre- 

 sented as separating, caudad, into a small dorsal branch (D) and a 

 larger ventral branch (C). Between these two forks, or, to be more 

 exact, between the ventral branch below and the caudal artery and 

 dorsal branch above, there is a pulsating heart (E), which communicates 

 anteriorly with the dorsal fork of the caudal vein, a short distance from 

 its union with the ventral fork. A valve is said to guard the entrance 

 of the heart into the vein. These observations of Jones', which were 

 microscopic, were made upon the tail of a small eel that had been placed 

 upon a thin plate of glass. Upon contracting, as is graphically shown 

 in Fig. 2, a colorless stream of lymph was seen to enter the vein. 

 Strange to say, Jones found no definite afferent lymphatic trunks 

 emptying into the caudal heart, and contends that such lymphatic 

 canals as were described by Miiller could not have escaped his attention. 

 Furthermore, Jones points out that since the lymphatic vessels of 

 Miiller are identical in position with the caudal blood vessels, that they 

 must be such. On p. 679, Jones gives the credit of the discovery of the 

 caudal heart in the eel to Hall in 1831, but it seems that Hall regarded 

 it as a blood heart. Continuing, Jones insists that the relation of the 

 blood vessels to the heart as set forth by Hall is incorrect, as Avill be 

 seen by comparing Hall's figure (see p. 679) to Fig. 1. Likewise 

 Jossifoo" overlooked the connection of the lymphatic system with the 



"Jones, T. W. "The Caudal Heart of the Eel a Lymphatic Heart," Phil. 

 Trans., 1868. 



"Jossifoo, S. M. "Snr les voles prlncipales et les organes de propulsion 

 de la lymphe chez certains Poissons," Archives d'anatomie microscopiqnc. 

 1906. 



