tion 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
blood is so divided in the ventricle itself, as to
appear pale. At each contraction of the ventricle, it
is collected into a drop of a vivid or deep red colour.
The action of this caudal heart is entirely
independent of the pulmonic heart; whilst the
latter beats sixty, the former beats one hundred and
sixty times in a minute. It continues for a very
long time after the influence of the pulmonic
heart is entirely removed.
As the pulsations of the caudal heart become
languid, distinct oscillations of the blood are seen
in the adjacent vessels, even to some distance
from the organ itself.
The vessels which issue from the caudal heart
appear to have a particular distribution to the
spinal marrow. A stilet passed down the spinal
canal, induced, in several instances, a distension
of the vessels leading to the caudal heart, and
frequently a slight extravasation of blood.
The capillary circulation and the pulsation in
the heart of the tail continued a few minutes
after the division of the animal, one inch and a
half below the pectoral fin ; hut the former soon
became oscillatory, and then ceased, whilst the
pulsation in the heart still continued.
Whether this structure be single, or multiplied,
whether it be peculiar to the eel, or common
to other fish, as animals having a pulmonic
heart only, or to other species characterized by the
length of their bodies, are questions which I
purpose to examine hereafter.
In the mean time I have ventured to designate
this singular organ by the term of the c a u d a l
h e a r t .