182 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [September 3,1870. 
THE SOURCE OF MUSCULAR POWER. 
BY BARON LIEBIG. 
The adherents of the doctrine that muscular power 
is generated by combustion of non-nitrogenous mate¬ 
rial in the muscles do not deny that the facts already 
stated have been established by experience, but they 
explain them in a different manner. 
That doctrine is, in part, based upon some facts 
which Fick and Wislicenus have established by their 
investigation into the source of muscular force ; they 
found that during the performance of measurable 
external work, viz. the lifting of their bodies to a 
certain height, the quantity of urea (or rather of ni¬ 
trogen) secreted meanwhile and within five hours 
following, corresponded to a quantity of albumen 
which would have barely accounted for one-tliird of 
the work, supposing the albumen to have been burnt 
and the heat generated expressed in terms of work. 
The nitrogen in the feces v r as not estimated. During 
the experiment only non-nitrogenous food v r as con¬ 
sumed. 
The inference drav r n from this observation v r as 
that the source of muscular power cannot be sought 
in the metamorphosis of muscular substance and its 
combustion; but that it must be generated by the 
transformation of non-nitrogenous constituents of 
food into oxygen compounds in the muscles. 
The calculation made by Fick and Wislicenus 
seems to be based on the idea that the production of 
force in muscles is analogous to the case of a gun; 
it is conceivable that from the volume of the gas 
formed by combustion of the powder, the projectile 
force of the bullet might be calculated; or that, from 
the distance traversed by the bullet, the volume of 
the gas might be calculated. If the process of force- 
production were similar to the combustion of gun¬ 
powder, then, under the assumption that the force 
was generated by combustion of muscular substance 
and that urea was a product of the change, the quan¬ 
tity of urea would in fact be proportionate to the 
work done; always presupposing that force and 
urea were produced at the same moment. If in this 
case, the quantity of urea secreted did not correspond 
to the work done, it would follow that, if the work 
were determined by combustion, other and indeed 
non-nitrogenous materials had taken the place of 
muscular substance, and combined wdtli oxygen. 
However, it cannot be assumed that non-nitro¬ 
genous food can furnish any special condition for 
the production of force, since it may be regarded 
as certain that two powerful men could have reached 
the Faulhorn inn without greater exhaustion even 
if they had not taken any food and if they had 
drunk only water instead of wine. In regard to the 
inference itself, this has evidently no special import¬ 
ance ; for if they had not eaten any non-nitrogenous 
food, it might have been assumed that the fat of their 
bodies had been consumed hi the place of such food. 
It does not appear to have been ascertained what 
the experimenters had lost in bodily weight after 
the experiment. Their conclusions w r ould, of course, 
be correct only if the assumptions on which they are 
founded were true. But the case may have been 
very different. 
It may be that the machine which w r e call organism 
possesses a much more perfect arrangement than is 
supposed according to the assumption of Fick and 
Wislicenus, perhaps one as perfect as a clock, which 
w r e are able to provide with force daily by winding 
it up, just as w r e provide the body with food every 
day, or which may be arranged so that in conse¬ 
quence of an accumulation of force, it will work for 
several days without any further supply of force. 
For maintaining the action of such a machine it is 
in both cases necessary, after the lapse of a certain 
time, to renew the supply of the force that has been 
expended hi producing motion; but once fully wound 
up, no further supply is necessary within certain 
limits. Whatever force is expended, within a given 
time, over and above the supply, must, of course, be 
made up for after that time by an increased supply, 
if the original condition is to be restored. 
Moreover, it may be that urea is not a product of 
the combustion of nitrogenous muscular material, 
and that its formation bears a relation to muscular 
work totally different from what Fick and Wislicenus 
have assumed. 
From their memoir it is not quite clear how they 
regard the conversion of heat, generated by combus¬ 
tion of non-nitrogenous material in muscle, into me¬ 
chanical effect as taking place. Frankland, who has 
adopted their view, expresses himself very definitely 
as follows:— 
“ The combustible food and oxygen coexist in the 
blood which courses through the muscle; but when 
the muscle is at rest, there is no chemical action 
between them. A command is sent from the brain 
to the muscle, the nervous agent determines oxida¬ 
tion. The potential energy becomes actual energy, 
one portion assuming the form of motion, another 
appearing as heat. Here is the source of animal heat , 
here the origin of muscular power! Like the piston 
and cylinder of a steam-engine, the muscle itself is 
only a machine for the transformation of heat into 
motion; both are subject to wear and tear, and re¬ 
quire renewal; but neither contributes in any im¬ 
portant degree, by its own oxidation, to the actual 
production of the mechanical power which it exerts.” * 
This passage represents the process of force pro¬ 
duction according to the view of Frankland and 
others who agree with him. 
Here urea and uric acid are regarded as the pro¬ 
ducts of the muscle used up. 
If this view were correct, it would follow that the 
muscular machine is one of the most imperfect ma¬ 
chines known, considering how large the daily waste 
in the shape of secreted urea would be. The fire¬ 
bars of a steam-engine furnace are not so rapidly 
used up. 
Certainly the wonderful construction of the animal 
body and its parts will remain long, and perhaps for 
ever, an insoluble problem; but the processes tailing 
place in its organs are of a physical or chemical na¬ 
ture, and it is unintelligible that oxygen and the 
combustible materials of the blood should require a 
command from the central organ in order to enter 
into combination. The share taken by the voluntary 
motor nerves in muscular activity must be of a totally 
different nature. 
However, it appears to me unnecessary to submit 
the views of Frankland, Fick and Wislicenus to 
closer criticism ; for I believe that, on the whole, those 
who have occupied themselves with the inquiry into 
the origin of muscular power have formed too easy an 
estimate of the problem, and that many years will 
elapse before it is possible to arrive at any definite 
conclusion as to what is really the nature of the 
question to be considered. 
* Phil. 3Iag. 4tli series, vol. xsxii. p. 194. 
