"9, NATURE AND LIFE. 
teristic of the anatomical elements is evolution, quite dis- 
tinct from nutrition. These little bodies, at the instant 
when they make their appearance, are not like what they 
are about to be at a later time. The more remotely from 
the moment of their birth we consider them, the more dif- 
ferent is the aspect we observe them to present from that 
they formerly had. They gain a larger bulk, and compli- 
cate themselves with new parts, with more perfect forms, 
which will vanish in their turn, so that every element thus 
describes a curve of evolution, of which the apex, repre- 
senting the full-grown state, is reached more or less rapidly. 
If nutrition and evolution belong to all anatomical ele- 
ments, contractility is the privileged mark of a very small 
number among them. It is peculiar to muscular fibres, in 
which it presents two modes: In the striated muscular 
fibres of animal life, it is sudden and quick; in the smooth 
fibres of organic life, it takes place slowly. It is upon this 
property that all movement and locomotion depend, since it 
is that which gives force to the muscles. 
Innervation is the peculiarity of the nerve-elements. 
Its manifestations are complex and diversified, but it is 
specially marked above all by this fact, that, far from lim- 
iting its play to a local action, it radiates from a distance 
and carries its influence far along. The nerve-cell, in fact, 
finds in the nerve-tubes issuing from it, in the congenerate 
cell which is appended to it, either conducting apparatus, 
designed to carry off the force which it produces, or a true 
receiving apparatus, designed to store up that forcé, and 
propel it at a distance under another form. A real electro- 
dynamic pair, as M. Luys has so well expressed it, the 
nerve arrangement thus reduced to its simplest expression, 
itself engenders the force which it transmits afar. It con- 
ducts, receives, and transforms it in the manner of those 
machines for electric transmission which represent, in the 
apparatus for generating electricity, the emitting cell in 

