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the human body precisely as in the use of the friction wheel or 
the voltaic buttery, i.e. } that eating and breathing are simply 
more refined forms of combustion and decomposition with whicli 
heat and motion are correlated. “ All this points to the con- 
clusion that the force we employ in muscular exertion is the force 
of burning fuel and not of creative will.” “ The body, in other 
words, falls into the category of machines.” “ The matter of 
the human body is the same as that of the world without us, 
and here we find the forces of the body identical with those of 
inorganic nature. Just as little as the voltaic battery, is the 
human body a creator of force. It is an apparatus exquisite 
and effectual beyond all others in transforming and distri- 
buting the energy with which it is supplied, but it possesses 
no creative power.” We have no disposition to dispute this. 
W e concede that so far as the production of muscular power is 
concerned and its transmutation into heat, all this may be true. 
We question very much, indeed, whether the experiments have 
been conducted with mathematical exactness, or whether the 
laws have been formulated with scientific precision or, as Tyndall 
phrases it, whether “ the interdependence” between the several 
factors has “ become quantitative — expressible by numbers.” 
But making nothing of this, and conceding that the law of 
conservation and correlation of muscular force operates as Prof. 
Tyndall contends, we cannot but inquire whether the human 
bodyperforms no other offices than these two, i.e., whether all the 
functions of life are resolvable into digestion, breathing, walking, 
climbing, and lifting weights ? Prof. Tyndall himself, it would 
seem, more than half suspects that his machine does something 
more than transmute force by eating and breathing. When 
he says : “ Thus far every action of the organism belongs to 
the domain either of physics or chemistry,” he bethinks him- 
self that the nerves have something to do with the applica- 
tion and direction of force, if not with its generation. These 
are sensor and motor. But these do not create force — they do 
not originate energy — they simply direct it, “ as Mayer says, 
with admirable lucidity, as an engineer by the motion of his 
finger in opening a valve, or loosening a detent can liberate an 
amount of mechanical energy almost infinite, compared with its 
exciting cause, so the nerves acting on the muscles can unlock 
an amount of power out of all proportion to the work done by 
the nerves themselves. The nerves, according to Mayer, pull 
the trigger, but the gunpowder which they ignite is stored in 
the muscles. This is the view now universally entertained.” 
We pass over the concession that has inadvertently dropped 
from the lins of our author, that work of some soi’t is done 
by the nerves themselves, which he had not noticed, and 
