September 10, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
201 
THE SOURCE OF MUSCULAR POWER. 
BY BARON LIEBIG. 
So far as anything is known of the processes of 
oxidation that take place at temperatures not ex¬ 
ceeding the heat of the body, the conversion of non- 
nitrogenous substances into carbonic acid and water, 
as well as the conversion of nitrogenous substances 
into carbonic acid, ammonia and water, takes place 
in the same way that urea is formed from uric acid. 
There are formed products containing less hydrogen 
and more oxygen, until at last the most highly oxy¬ 
genated product yields carbonic acid by a further 
addition of oxygen. Thus alcohol is converted first 
into aldehyd, then into acetic acid; this again into 
formic acid, which then yields carbonic acid. 
The liiglily complex nitrogenous compounds always 
undergo at first a breaking up into products that on 
the one hand contain a larger amount of nitrogen, 
while the others are free from nitrogen, or contain a 
smaller amount of it with a larger amount of carbon. 
These products are then converted, like uric acid and 
non-nitrogenous substances, into carbonic acid, am¬ 
monia and water. 
Urea may be regarded as carbonic acid, in which 
one equivalent of oxygen is replaced by amidogen, 
or as ammonia in which the third equivalent of hy¬ 
drogen is replaced by carbonic oxide. 
r O •) n H 2 7 
c nh 2 ) or N co) 
In the animal body oxidation of noil-nitrogenous 
compounds takes place in the presence of alkalies, and 
in many cases I believe the law of oxidation disco¬ 
vered by Kolbe also obtains. This explains the 
formation of substances containing little or no oxy¬ 
gen out of others that contain much.* 
From what has been said it will be intelligible 
that muscular power, if its source is in the muscles, 
does not originate by combustion taking place in the 
same way as in the furnace of a steam engine; it 
can only be the result of a material transformation, 
that is to say, of motion taking place in the interior 
of the muscles. 
A closer consideration of the behaviour of yeast- 
cells is perhaps calculated to afford a more definite 
idea of the process that takes place in the living 
muscle. 
Whatever view one may hold in regard to the mode 
in which the yeast-cell acts upon sugar, it is at least 
certain that within the yeast-cell there is motion, by 
means of which it acquires the capability of perform¬ 
ing external work, consisting in the breaking up of a 
carbohydrate and similar compounds. This work, 
however, is chemical not mechanical, as it would be 
if a piece of wood were split. 
Some notion of the magnitude of the force exerted 
in the action of yeast may be formed from the fact 
that a particle of yeast will bring about the conver¬ 
sion of at least sixty times its weight of sugar, or, as 
I believe, even upwards of a hundred times its 
weight. 
This breaking up of sugar is accompanied by a 
considerable evolution of heat, and by a mechanical 
effect. According to Dubrunfaut’s direct determina¬ 
tion, 1 gram of sugar evolves in fermentation 127 
units .of heat; in addition to tins, the carbonic acid 
gas disengaged has to overcome the pressure of the 
atmosphere, thu s performing work that must be taken 
* Ann. Chem. Pharm. lxx. 318. 
Third Series, No. 11. 
into account as corresponding to 2482 gram-meters 
for each gram of sugar. 
Assuming then that yeast decomposes sixty times 
its weight of sugar, it follows that if the evolution of 
heat and the exercise of force be referred to the yeast 
alone, without regard to the sugar, each gram of 
yeast is capable of developing G X 127=7620 units of 
heat, and a mechanical effect equal to 148,960 gram- 
meters, or very much more than it would produce by 
combustion, and that is done without the access or 
co-operation of oxygen. 
Supposing a system of pipes and vessels as deli¬ 
cate as the blood-vessels in the muscles, and the 
walls of those vessels to be forming entirely of yeast- 
cells, with a stream of sugar solution moving through 
these vessels, we should then, by the determination 
of the heat generated and the mechanical action 
produced, be forced to regard this apparatus as a 
very enormous source of heat and power. 
If we knew no more of sugar and of the behaviour 
of yeast in fermentation than we know of blood and 
muscle in the work performed by muscles, we should 
not be in a position, by the determination of the de¬ 
crease of weight in the system and of the heat of 
combustion of the substances that the system con¬ 
sists of, to form any conception of the magnitude of 
the causes acting in it. 
If in place of sugar solution we suppose that a cur¬ 
rent of beer-wort (which includes conditions for the 
multiplication of active yeast-cells) flowed through 
the system of yeast-cells, then the loss of weight 
undergone by the working cells would be made up 
for by the production of new cells; the system would 
increase in mass and circumference, while its action 
would be proportional to its largest section. 
On the presumption that in the alteration undergone 
by sugar in its passage through the supposed system 
of cells, we might undoubtedly ascribe the carbonic 
acid and the heat produced, as well as the mechani¬ 
cal effect (which are indications of an oxidation pro¬ 
cess) to combustion, then we might compare the pro¬ 
cess to that taking place under the boiler of a steam- 
engine, and the parts of such an engine with the ap¬ 
paratus consisting of cells. 
However, this representation would be entirely 
false : the oxygen of the air may take part in the 
process of fermention, as in the conversion of alcohol 
into acetic acid, but it is not the determining cause 
of it; the carbonic acid evolved and the heat developed 
are not products of combustion. 
The cause to which all these actions must be 
ascribed lies in the mobile cell contents and in the 
motion to which that is subject. 
If we compare the behaviour of a muscle with that 
of the yeast-cell, we know that a constant metamor¬ 
phosis or motion is taking place in it, and that this 
goes on even when the muscle is separated from the 
body. During this alteration the muscle is capable 
of performing a certain amount of mechanical work; 
the internal or molecular motion in the muscle is 
quite independent of the exterior motion of the mass; 
it takes place during rest and in the absence of irri¬ 
tation, without the muscle showing any sign of ex¬ 
ternal motion ; but the latter is dependent upon the 
internal motion, and when this has attained a certain 
magnitude the power of the muscle for performing 
mechanical work is extinguished. 
This behaviour corresponds exactly to that of the 
yeast-cell; the transformation of its cell contents is 
quite independent of the sugar. 
