1864.] Carrnnrer on Correlation of Physical and Vital Forces, 265 
structive force than is required for the maintenance of its integrity ; 
but there seems evidence that even then the required force has to be 
supplied by a retrograde metamorphosis of a portion of the constituents 
of the food, over and above that which serves to generate Animal 
Heat. For it has been experimentally found that, in the ordinary life 
of an adult Mammal, the quantity of food necessary to keep the body 
in its normal condition is nearly twice that which would be required 
to supply the “waste” of the organism, as measured by the total 
amount of excreta when food is withheld; and hence it seems almost 
certain that the descent of a portion of the organic constituents of this 
food to the lower level of simple binary compounds is a necessary 
condition of the elevation of another portion to the state of living 
organized tissue. 
The conditions of Animal existence, moreover, involve a constant 
expenditure of Motor force through the instrumentality of the Nervo- 
muscular apparatus ; and the exercise of the purely Psychical powers, 
through the instrumentality of the brain, constitutes a further expen- 
diture of force, even when no bodily exertion is made as its result. 
We have now to consider the conditions under which these forces are 
developed, and the sources from which they are derived. 
The doctrine at present commonly received among Physiologists 
upon these points may be stated as follows :—The functional activity 
of the nervous and muscular apparatuses involves, as its necessary 
condition, the disintegration of their tissues; the components of 
which, uniting with the oxygen of the blood, enter into new and 
simpler combinations, which are ultimately eliminated from the body 
by the excretory operations. In such a retrograde metamorphosis of 
tissue, we have two sources of the liberation of force ;—first, its 
descent from the condition of living, to that of dead matter, involving 
a liberation of that force which was originally concerned in its organi- 
zation ;*—and second, the further descent of its complex organic com- 
ponents to the lower plane of simple binary compounds. If we trace 
back these forces to their proximate source, we find both of them in 
the food at the expense of which the Animal organism is constructed ; 
for besides supplying the material of the tissues, a portion of that food 
(as already shown) becomes the source, in its retrograde metamor- 
phosis, of the production of the Heat which supplies the constructive 
power, whilst another portion may afford, by a lke descent, a yet more 
direct supply of organizing force. And thus we find in the action of 
Solar Light and Heat upon Plants—whereby they are enabled not 
* It was by Liebig (‘Animal Chemistry, 1842,) that the doctrine was first 
distinctly promulgated which had been already more vaguely affirmed by various 
Physiologists, that every production of motion by an Animal involves a pro- 
portional disintegration of muscular substance. But he seems to have regarded 
the motor force produced as the expression only of the vital force by which the 
tissue was previously animated; and to have looked upon its disintegration by 
oxygenation as simply a consequence of its death. The doctrine of the ‘“ Corre- 
lation of Forces” being at that time undeveloped, he was not prepared to 
recognize a source of Motor power in the ulterior chemical changes which the 
substance of the muscle undergoes ; but seems to have regarded them as only 
concerned in the production of Heat. 
