IV, AND REVIVED. | 143 
a yoluntary mufcle, which beats at the will of 
the animal ; that is, when it protrudes the fibrilli 
and forms the vortex: and this /pontaneity, if 1 
may ufe the expreflion, has, before me, been obe 
ferved by others, Are there animals whofe heart 
beats by intervals, fo that pulfation may ceafe 
when the animal chufes? Wheel animals fome- 
times remain feveral weeks alive in water without 
making the vortex, confequently without moving 
the heart. Is it poflible that any animal can 
exift fo long without pulfation of the heart, the 
animating fpring of the whole machine? Thefe 
are two paradoxes which may be no lefs true 
than others more wonderful, fuch as the refurrec- 
tion of the wheel animal. Though this particle 
may be thought a real heart, either from perform- 
ing functions fimilar, from its fituation in the re- 
gion of the breaft, from contraction and dila- 
tion like another heart, ftill thefe are not con- 
vincing reafons, becaufe it may be an organ def: 
tined for very different purpofes, I ought to fay, 
as I think, that it is more natural to believe it to 
be-an organ ferving for the aliments ; and that 
the contraction and dilation is for receiving the 
food and tranfmitting it to the ftomach. Such 
an hypothefis will eafily explain why it is in mo- 
tion only while the vortex is formed: it is be- 
caufe aliment is then drawn to the mouth and 
 tranfimitted to the body. If the part remains long 
motionlefs, 
