August G, 1870.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
101 
ALCOHOLIC FERMENTATION. 
EY BARON VON LIEBIG. 
(Continued from p. 84.) 
It lias already been mentioned tliat many organic 
compounds are known wliich undergo, in presence of 
water, alteration and metamorphosis having a cer¬ 
tain duration, and ultimately terminating in putre¬ 
faction ; while other organic substances that are not 
liable to such alteration hy themselves, nevertheless 
suffer a similar displacement or separation of their 
molecules when brought in contact with the former, 
like sugar in contact with yeast; but without the 
aid of vital action. 
When the molecular work, or the metamorphosis 
of the cell-contents ceases, its action upon sugar 
ceases likewise; thus, for example, yeast may be 
kept for many months in a weak solution of creasote,* 
carbolic acid,f or other solution containing a certain 
amount of alcohol and acid, like wine, without any 
reduction of its efficacy. 
It is intelligible that the products formed from the 
nitrogenous and sulphuretted constituents of yeast 
in the fermentation of yeast alone, cannot be identical 
with those formed from it by contact with sugar, be¬ 
cause the sugar, penetrating into the cells, reacts 
upon the contents, and thus the re-arrangement of 
the particles of nitrogenous substance is effected. 
Moreover, the liquid filtered from yeast submitted to 
fermentation by itself is rich in nitrogenous sub¬ 
stances, and it is very suitable for cell production. 
I have mentioned that yeast loses its power of fer¬ 
menting when exposed to a temperature of 00° C.; in 
like manner active fermentation in a saccharine liquid 
is stopped when the liquid is heated to 00° C., and it 
does not recommence again on cooling the liquid. 
Pasteur’s admirable method of making wine keep by 
heating it to 60° C., appears to be in some way con¬ 
nected with this influence of heat upon yeast. 
I have observed that during the putrefaction of 
yeast, the power of producing fermentation in sugar 
solution is retained for a long tune. The point at 
which putrefaction sets in is easily recognizable 
when the yeast is mixed with some nitre solution. 
While fermenting alone or with sugar solution, no 
alteration of the nitre is caused; but so soon as pu¬ 
trefaction begins, the nitrate is converted into nitrite, 
and on testing some of the liquid with starch, iodide 
of potassium, and dilute sulphuric acid, a deep blue 
colour is produced. 
A quantity of yeast was left for five weeks after 
the commencement of putrefaction, and every four 
days a portion of it was added to sugar solution. 
Even after it had passed into an extremely putrid 
state, it produced fermentation, and then the bad smell 
disappeared gradually. However, the quantity of 
alcohol formed became less, and there were formed 
besides Carbonic acid, other products that I have not 
yet examined. 
In reference to the formation and development of 
the yeast-fungus, Pasteur has made an observation 
which has given a new direction to the views pre¬ 
viously entertained. 
It was supposed that yeast was developed like 
other fungi, wliich, as parasites, derive their con¬ 
stituents from plant or animal remains, especially 
that its propagation and multiplication required al¬ 
buminates, or some derivative of them besides phos¬ 
phates. 
Pasteur’s experiments, however, leave no doubt 
that yeast may develope in mixtures containing tar¬ 
trate of ammonia, sugar, and the cell-constituents 
of yeast. 
It is astonishing that this discovery has not at¬ 
tracted more attention in regard to a special point, 
for it comprises a fact of very great significance for 
physiology, viz., the formation of albuminate in 
plants, respecting which we are in possession of 
scarcely anything beyond conjectures; hitherto this 
has been regarded as one of the greatest mysteries 
in organic nature. 
We have regarded the organic acids in plants— 
oxalic, malic, citric, etc.—as the intermediate sub¬ 
stances between carbonic acid and sugar, starch, 
cellulose, etc., hy means of which the gradual tran¬ 
sition from carbonic acid to a plant-constituent is 
effected; but in the food plants, which contain the 
largest amounts of albuminates, we do not find any 
nitrogenous substance besides ammonia that can be 
connected with the formation of the albuminates. 
Tins problem appeared to be solved by the experi¬ 
ments of Pasteur; for if }^east-cells, placed in a 
mixture of ammonia, tartaric acid, sugar, and phos¬ 
phate, could propagate and multiply, it is evident 
that an albuminate must have been formed from the 
elements of this mixture, since one of the chief con¬ 
stituents of the yeast-fungus is an albuminate, and 
in each of the new yeast-cells there must be a certain 
quantity of freshly-produced albuminate present, 
without the presence of which no true yeast-cell 
could have been formed. 
Twenty-five years ago I directed attention to the 
possibility that albumen in plants might be formed 
by combination of ammonia with sugar, attended 
with elimination of water. 
Sugar .. . C 43 H 4S 0 4S ) ( Protein. C 48 H 36 0 14 N 6 
Ammonia H ls N 6 } = j Oxygen. 0 4 
’ l Water . H 30 O 30 
^ 43 ^ 66 ^ 43^6 ^ 43 ^ 66 ^ 43^6 
The substance here referred to under the name of 
protein contains the same elements as casein, united 
in the same proportions, leaving out of consideration 
sulphur, the precise origin of which I am not able to 
account for. 
The idea of the production of an albuminate from 
ammonia and sugar was not therefore at all sur¬ 
prising to me, but rather familiar than otherwise; 
nevertheless, I could not readily conceive such a 
mode of formation to obtain in a fungus, for it 
would not be possible without elimination of oxygen 
from the sugar, while the yeast-fungus grows in the 
total absence of light, and up to the present time no 
evolution of oxygen has been observed in the growth 
of fungi. 
On closer consideration of the experiments which 
preceded Pasteur’s chief experiments, and led him 
to them, it is scarcely possible to suppress some 
misgivings. Thus, for instance, Pasteur added to a 
sugar solution some tartrate of ammonia, and, after 
fermentation, he found less ammonia than he had 
added, inferring thence that the missing ammonia 
had entered into combination and contributed to 
the production of yeast. The details of the three 
# Beckamp. f Dr. v. Pettenkofer. 
Third Series, No. 6. 
* In a note on the origin of albumen, Ann. Ch. Pli. li. 287 
