82 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[July 30, 1870. 
accompanied by a decomposition of tlie cell contents, 
from which a nitrogenous substance is dissolved by 
the fermenting liquid. This liquid loses nitrogenous 
constituents if these become part of the cells, and it 
again receives some by the decomposition of the cell 
contents. 
So far back as 1853, Graham, Hofmann, and 
Redwood ascertained that a hopped wort of pale 
malt, containing ’217 per cent, of nitrogen before 
fermentation, contained only T34 per cent, after 
fermentation, so that only '083 per cent, of the ni¬ 
trogen remained in the yeast, the rest remaining in 
the fermented liquid. The numerous nitrogen deter¬ 
minations in beer by Feichtinger,* etc., showed a con¬ 
stant, and on the average, larger amount of nitrogen 
in Bavarian beer. 
According to experience in brewing, the yeast 
added for setting up fermentation is mcreased eighteen 
or twenty-fold, or there is obtained from 1800 to 
2000 parts for each 100 parts of pasty yeast. 
In the fermentation of sugar with yeast there can¬ 
not be any increase of yeast, for there is no substance 
containing nitrogen and sulphur to serve as food for 
the yeast-cells. Pasteur has formed a peculiar opi¬ 
nion respecting this process. He says, “If tliis 
matter be examined more closely, it will be evident 
that in the fermentation of sugar in the presence of 
albuminates there is not more, but rather less yeast 
formed than in the fermentation of pure sugar solu¬ 
tion.” If increase of yeast means addition and mul¬ 
tiplication of the yeast-cells, this assertion of Pasteur’s 
is perfectly unintelligible and inconsistent with the 
facts ascertained by himself. In one of his experi¬ 
ments he added 20 c. c. of an aqueous decoction of 
yeast, containing '331 nitrogenous substance, to a 
solution of 9’890 grm. sugar, and then added a trace 
of yeast. After the fermentation had ceased, this 
yeast had increased to T52 grm. of dry yeast. If this 
trace of yeast weighed 2 milligrams this increase 
would be about seventy-sixfold, or 100 parts of yeast 
would have given 7000 parts. 
In his experiments with sugar-water and yeastf 
100 grm. of sugar was fermented with 4 - 625 grm. 
yeast, and the yeast weighed, after fermentation, 
3'230 grm., having lost 30 per cent. In another ex¬ 
periment 100 parts of yeast were reduced to 91 parts. 
Comparing the increase of weight in the first men¬ 
tioned experiment with the other, in which it was 
only 42 per cent., the large difference appears re¬ 
markable, and the cause of it is easily intelligible, 
for in the former case there was a substance present 
that served for the increase and propagation of the 
yeast-cells, while in the other case the fermentation 
took place in pure sugar solution. 
By increase of yeast nothing else can be under¬ 
stood but multiplication of yeast-cells, and this pre¬ 
supposes the presence of a nitrogenous substance for 
the production of their nitrogenous contents. It is, 
therefore, impossible to suppose, that in the fermen¬ 
tation of sugar with yeast there can be any multi¬ 
plication of active yeast-cells, and any increase of 
weight must be due to some other cause. 
However, Pasteur adopted entirely different as¬ 
sumptions for establishing his statement. When a 
fermented sugar solution is evaporated to dryness, 
and the residue treated with alcohol and ether," there 
* Ann. Ch. Pli. vol. cxxx. p. 227. 
f Page 401. 
remains a nitrogenous substance whose constituents 
Pasteur regards as originating from the yeast. He 
describes it as the “ soluble part of the yeast that 
passes into solution during the fermentation,” and 
he considers that it must be added to the yeast re¬ 
maining after fermentation, in order to ascertain the 
actual increase of weight. 
It is in this way that he makes the dissolved 
contents of the fermented liquid in the experiment to 
amount to 2'320 grm., and adding this to the yeast 
residue = 3'230 grm., obtains 5'550 grm. as the total 
quantity of yeast, or ’934 grm. more than the quantity 
taken at first. In this way he makes the deficiency 
of 33 per cent, appear as a surplus of 20 per 
cent. It is quite true that the liquid, after fermenta¬ 
tion, contains in solution a nitrogenous substance 
that must have originated from the yeast; but the 
whole of the residue obtained by evaporating this 
solution cannot be regarded as originating from 
yeast, and Pasteur has himself given the most con¬ 
vincing proof of this. 
In the fifth section of liis Memoir, headed “ Suc¬ 
cinic Acid, Glycerine, Alcohol, and Carbonic Acid 
are not the only Products of Vinous Fermentation," 
he describes an experiment in which he fermented 
100 grm. of sugar with yeast, and then determined 
the succinic acid, glycerine, and extractive material. 
The yeast taken weighed 1T98 grm.; the extract 
(free from succinic acid and glycerine) 1T30 grm., 
and the remaining yeast P700, so that the extract 
weighed only 68 milligrams less than the yeast taken. 
Therefore, it is self-evident the greater part of this 
extract could not have been derived from the yeast, 
otherwise there would not have been any yeast left 
after the fermentation, while, in fact, there was more 
than the quantity taken at first. 
The experiments of Graham, Hofmann, and Red¬ 
wood may also be considered in reference to Pasteur’s 
observations, as furnishing additional evidence that 
the greater part of the residual extract does not ori¬ 
ginate from yeast. They mention that in the fer¬ 
mentation of sugar, however far it is pushed, there 
is formed, besides alcohol and carbonic acid, a pecu¬ 
liar substance; this is the case with pure sugar 
solutions as well as with beerwort. A solution of 
cane sugar mixed with 14, 3, and 6 per cent, by 
measure of liquid yeast gave, after fermentation, 4 - 4, 
3‘72, and 3 7 per cent, of that substance, the cha¬ 
racters of which resembled those of glucic acid or 
caramel. It was not susceptible of further fermen¬ 
tation, and presented the appearance of a dark brown 
syrup, with a bitter and rather acid taste. Though 
a mixture of various substances, it did not contain 
any dextrin or sugar, but precipitated suboxide when 
boiled with an alkaline solution of copper. It is 
true these residues were not washed with alcohol 
and ether before weighing; but comparing their 
weight with the quantities of yeast taken in the 
different experiments, it is evident there is no rela¬ 
tion between the two; with two or three times as 
much 3 r east, there was no more extract than where 
the smaller quantity was taken, and it must be re¬ 
membered that neither succinic acid nor glycerine 
reduce alkaline solution of copper. Consequently, it 
is not admissible to regard the extractive material 
contained in a fermented liquid as being derived 
from the yeast, and to take it into account as re¬ 
sidual yeast as Pasteur does. 
In a saccharine solution containing nitrogenous 
and sulphuretted material suitable for the food of 
