PROFESSOR T. WHARTON JONES ON THE CAUDAL HEART OF THE EEL. 681 
That Professor Milne-Edwards labours under a mistake in thus attributing to Pro- 
fessor Muller the recognition of the true nature of the caudal heart of the eel is evident 
from the following facts : — 
Professor Muller, as we have seen, indeed remarks, in his paper in Poggendorff’s 
‘Annalen ’ above referred to, that “ further observations must teach whether the function 
of this organ is to propel the lymph of the tail into the end of the caudal vein.” But a 
reference to the quotations, also above given, from Professor Muller’s paper in the Phi- 
losophical Transactions for 1833, and his paper in the ‘ Archiv ’ for 1842, p. 477, as well 
as from his ‘Elements of Physiology,’ by Balt, 2nd edition, 1839, pp. 216 and 245, 
shows that Professor Muller did not in these more recent writings dissent from Dr. 
Marshall Hall in the opinion he entertained that the “ caudal heart ” in the eel belongs 
to the blood-vascular system. 
So far as I have been able to ascertain, no one has hitherto given a correct explanation 
of the phenomenon of small drops of red blood propelled in rapid succession, as if from 
the caudal heart, along the caudal vein. 
Without first showing that these drops of blood or agglomerations of red corpuscles 
are not propelled from the heart, and without showing that it is colourless lymph alone 
which is really propelled from the heart, no one could have been warranted in dissenting 
from Dr. Marshall Hall’s view as to the nature of the caudal heart of the eel, or in 
pronouncing, how correctly soever, that organ to be a lymphatic heart. 
I now come, in conclusion, to the alleged anticipation of Dr. Marshall Hall’s dis- 
covery of the “ caudal heart ” by Leeuwenhoek. 
Professor Milne-Edwards, adopting Professor Muller’s reading of Leeuwenhoek, as 
above quoted, more decidedly than Professor Muller himself, says : — “ Cet organe a ete 
vaguement aperQu, il y a pres de deux siecles, par Leeuwenhoek, mais n’avait que peu 
attire l’attention cles physiologistes, lorsque, en 1831*, Marshall Hall publia a ce sujet 
des observations qu’il croyait etre completement nouvelles.” 
In regard to this claim for Leeuwenhoek, I have not been able to satisfy myself that 
there is any foundation for it. 
Leeuwenhoek’s words in his 66th Epistle, which was addressed to “ Nobilissimi Viri,” 
the Fellows of the Royal Society of London, ‘ Opera Omnia,’ tom. ii. p. 174, the reference 
given by Professor Milne-Edwards, are : — 
“ Vidi quoque in omnibus arteriis, licet minutissimis, assidue, ac celeriter novam fieri 
accelerationem protrusionis in sanguine, ubi vero attenderem ad magnam arteriam in 
cauda jacentem, ibi protrusio sanguinis, a corde facta, multo erat vehementior.” 
Again, at page 175, Leeuwenhoek says: — 
“ Imo etiam fere semper quam proxime ad pinnae extrema in tenuissimis vasis sangui- 
feris, singulis momentis novae protrusionis, quam sanguis a corde accipit accelerationem 
dignoscere poteram.” 
How far, with the knowledge of Dr. Marshall Hall’s discovery, the words “ ubi vero 
* 1836 is put down, but evidently by mistake. 
