on which the action of the heart depends , &c. 83 
nervous, so has the nervous, independent of the sensorial 
system. 
What is here said is finely illustrated by reviewing the 
various classes of animals. In the lowest class we find only 
the muscular system, which exists without either nervous sys- 
tem or sensorium. In the next class we find the muscular 
and nervous systems, which exist without sensorium. In the 
most perfect animals, we find the three vital powers combined, 
each having an existence not immediately depending on the 
others, but all so connected, that none can exist long without 
the others. The nature of this connection is obvious, when 
we consider that all are supported by the circulation, which 
depends for its immediate support on the muscular system, and 
cannot long exist without respiration, and that this depends 
not on the sensorium, but, as M. i.e Gallois has satisfactorily 
proved, on the nervous system, which system is under the 
immediate influence of the sensorium, directing, but not pro- 
ducing, its various movements : and such is the power of the 
sensorium over the nervous system, that its affections may, 
through this system, at once destroy every function of life. 
Thus joy and other strong passions have killed more speedily 
than suffocation can, and therefore otherwise than through 
the destruction of respiration. 
Exp. 20. All that has been said of the vital power of the 
heart is strikingly confirmed by the following experiments. If 
the head and spine of a frog be removed, the heart continues to 
perform its function perfectly for many hours, nor does it seem 
at all immediately affected by their removal. But we find 
the effect very different when the most sudden and powerful 
agent is applied to them. If they are destroyed by being cut 
M 2 
