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of Edinburgh^ Session 1863 - 64 . 
is admitted ; that that directive principle operates through organic 
structure and the protoplasma in vegetable bodies, botli of which 
owe their origin in unvaried succession to the original parents of 
the species ; that all organic structure at present in existence may 
be traced back to the state of vegetable protoplasma ; that the 
protoplasma in the cells of the green parts of plants becomes aug- 
mented by the assimilation of carbon and hydrogen in particular, 
derived from the carbonic acid and water of the atmosphere, and 
that this operation is purely chemical, aided by the merely physical 
agency of light ; that the presence of water in so large proportion 
throughout the living solids, pervading their atoms and interstices 
like an almost incompressible atmosphere, accounts for many of 
the peculiarities of organic affinity, and among others for the 
apparent antagonism between the attraction which holds together 
the living solids and that which, on the failure of vital action, so 
quickly reduces them to the state of purely mineral matter — the case 
being exactly parallel to that of water containing salts in dilute 
solution, the concentration of which is followed by the precipitation 
of such insoluble salts as can arise out of the constituents of the 
salts originally dissolved in the fluid — finally, that the heat which 
attends the exercise of such affinities as produce water and carbonic 
acid is due to the rapid movement of the strongly attracted atoms, 
that being to a far greater degree than in the exercise of the 
organic affinities. 
It is next considered how far electricity is to be regarded as con- 
cerned under a directive principle in the phenomena of life, and 
particularly in the exertion of animal power. 
The facts ascertained with respect to electrical fishes are pointed 
to as sufficient proof, that animals nourished and constituted like 
vertebrated animals can generate a great amount of electrical force, 
the peculiarities of the electrical fishes being in fact inconsider- 
able, when compared with the effects produced. It is further noticed, 
that the general result of the many experiments made by recent 
electro-physiologists is to show, that during life, hardly any two 
parts of the animal body are in electric equilibrium. From all which, 
and many other facts, there, appears to be nothing improbable in 
the idea that electricity is an active agent in the phenomena of life, 
more especially in those of the nervous apparatus and the muscular 
