310 NATURE AND LIFE. 
physiologist styled the vital knot, and in which he professed 
to lodge the principle of life itself? The point which Flou- 
rens regarded as this vital knot is situated nearly at the 
middle of the prolonged spinal cord—that is, the middle 
of that portion of the nerve-substance which connects the 
brain with the spinal marrow. This region, in fact, has a 
fine and dangerous excitability. A prick, or the penetra- 
tion of a needle into it, is enough to cause the instant death 
of any animal whatever. It is the very means used in 
physiological laboratories to destroy life swiftly and surely _ 
in dogs. That susceptibility is explained in the most nat- 
ural way. This spot is the starting-point of the nerves 
that go to the lungs; the moment that the slightest injury 
is produced in it, there follows a check on the movements 
of respiration, and ensuing death. This vital knot of Flou- 
rens enjoys no sort of special prerogative. Life is not 
more concentrated nor more essential in it than elsewhere; 
it simply coincides with the initial pomt of the nerves ani- 
mating one of the organs indispensable to vitality, the or- 
gan of sanguification ; and in living organisms any altera- 
tion of the nerves controlling a function brings a serious 
tisk as to its complete performance. There is, therefore, 
no such thing as a vital knot, a central fire of life, in ani- 
mals. They are collections of an infinity of infinitely small 
living creatures, and each one of these microscopic living 
points is its own life-centre for itself. Each on its own 
account grows, produces heat, and displays those charac- 
teristic activities which depend upon its structure. Each 
one, by virtue of a preéstablished harmony, meets all the 
rest in the ways that they require; but, just as each lives 
on its own account, so on its account each dies. And the 
proof that this is so is found in the fact that certain parts 
taken from a dead body can be transferred to a living one 
without suffering any interruption in their physiological 
activity, and in the fact that many organs which seem dead 
