THE FAMTLT OF EELS. 
323 
fishes are better qualified to discern external objects, or to 
employ their faculties in their own pursuits; and several 
instances have been mentioned of the consciousness they have 
shewn of kind treatment, so as to have become familiar with 
those who olfered them food. Aristotle has noticed that they 
were attracted with agreeable scents, and Ellis says of some 
in the South Sea Islands that they came to be fed at the 
sound of a sharp whistle. 
The remarkable sensibility of touch in the tail of this 
family of fishes has been already noticed, but we owe to Dr. 
Marshall Hall the knowledge of a particular organization of 
the blood-vessels of this part, which beyond doubt is closely 
connected with the uses to which this organ is sometimes 
applied. This eminent inquirer remarks, “It has been supposed 
that the pulmonic heart alone, with the aid of some subsidiary 
powers of the circulation, propelled the blood. I have dis- 
covered in one species of fish that which will lead us to 
view this opinion with distrust, and which will point out to 
us the fact of an unsuspected addition to the power and 
action of the heart in some species of animals. This structure 
is seen, even with the naked eye, in the tail of the Eel. 
Its form, action, and connexions are, from the degree of 
transparency of the part, still better traced by the assistance 
of the microscope. Placed under this instrument, a particular 
spot near the extremity of the tail of the Eel, easily dis- 
covered, has the appearance represented” in “the drawing of 
the ventricle of this caudal heart. The different vessels unite 
and form a connexion with this ventricle near its highest 
point.” 
The course pursued by the blood in these vessels “uniformly 
tends towards the highest point of the ventricle; from this 
point it seems to be slowly propelled or drawn into the ventricle ; 
by a sudden contraction of this it is gathered into a drop, and 
propelled with great velocity, and at first with the peculiar 
appearance of successive drops, along a vessel which ascends 
along the inferior spinal canal, .and which must, although it 
pursues a direction towards the heart, be considered an artery.” 
“The action of this caudal heart is entirely independent of the 
pulmonic heart; while the latter beats si.xty, the former beats 
one hundred and sixty times in a minute. It continues for a 
