62 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[July 23, 1S70. 
part. That being the case, it remains to explain 
what the relation of the physiological process in 
the formation of yeast may have to this substance, 
which obviously acquires its peculiar power of ex¬ 
citing fermentation only when it becomes a consti¬ 
tuent of yeast. 
It might be that the physiological process had no 
other relation to fermentation than that of determin¬ 
ing the production of the material which induces the 
alteration of sugar and other organic molecules, by 
an action peculiar to itself,—like that of emulsin 
upon salicin or amygdalin. In that case the phy¬ 
siological process would be necessary for the pro¬ 
duction of that material, but it would have no further 
connection with the phenomena of fermentation. 
Some experiments I have made in this direction 
will, perhaps, contribute towards the elucidation of 
the subject. 
There is no doubt as to the nature of beer and 
wine yeast. It is a form of development of various 
fungi, and, when washed, consists of cell-membrane 
enveloped in primordial vesicle, a granular mucous 
substance, protoplasm, and a watery cell-liquid lying 
in the protoplasm as drops of various size. “ By di¬ 
gesting in distilled water the globules increase in 
size, sometimes until their outer surfaces nearly 
touch the cell walls. This result is connected with 
the swelling up of the yeast-cells, and, like it, is due to 
membranous diffusion, by which water gains access 
to the cells, while the cell contents escape into the 
water.”* 
“ Solution of iodine colours the cells faintly yel¬ 
low; sugar and sulphuric acid produce a scarcely 
more distinguishable rose colour, indicating probably 
that the amount of albuminous substance has been 
considerably reduced by the action of water, f 
I am in doubt whether the substance extracted 
from yeast by water is really albuminous. When 
one litre of fresh pasty yeast is washed by decanta¬ 
tion four times in succession with six or eight times 
its volume of water, and the residue digested with 
four litres of water for three or four hours, only a 
small quantity of organic substance is extracted, 
less than 350 milligrams per litre of water, and the 
power of the yeast to excite fermentation is scarcely 
at all reduced. When the washed yeast is left for a 
long time with its own volume of water, the amount 
of organic substance in the water is increased ten¬ 
fold, and what is thus extracted appears to be pro¬ 
duced by decomposition of a constituent of the 
yeast. This substance communicates very remark¬ 
able properties to the water. Crystalline cane-sugar 
dissolved in it is rapidly converted into grape-sugar. 
Even within a few minutes Fehling’s test gives a 
copious precipitate of suboxide of copper. The 
liquid has a very slight acid reaction, is without 
taste or colour; with basic acetate of lead and tan¬ 
nin it becomes slightly milky; after standing for 
some days exposed to the air it loses its transpa¬ 
rency, and a white flocculent precipitate is formed. 
To form some idea of the action of this organic 
substance on cane-sugar, I dissolved various quanti¬ 
ties in the yeast-water, and estimated the grape-sugar 
formed after twenty-four hours. It appeared that 
25 grm. dissolved in 100 c. c. was fully converted 
within twelve hours. This 100 c. c. of solution con¬ 
tained ’39 grm. of the organic substance, and I be- 
* Lermer. 
f According to Dr. Lermer’s microscopic examination. 
lieve that a much larger quantity of sugar was con¬ 
verted in the same liquid. By heating this liquid to 
boiling it entirely lost its power of affecting sugar. 
There can scarcely be any doubt as to the cause 
of this action, for yeast-water contains material in a 
state of change, and the conversion of cane-sugar 
into grape-sugar must be determined by that state of 
motion. The particles of cane-sugar behaved as if 
they were parts or constituents of the nitrogenous 
material, and they underwent transposition. Contact 
with a very small quantity of this changing material 
produced the same effect as contact with mineral 
acids,—the same effect as powerful chemical afffnit}". 
A similar phenomenon is the action exercised by 
ethyl aldehyd upon cyanogen in aqueous solution ; 
a very small quantity of aldehyd added to this solu¬ 
tion determines the formation of oxamide by the 
union of the cyanogen with two atoms of water. 
Evidently the aldehyd (part of which is converted 
into a substance resembling acrolein during this 
change) produces an effect which consists in a re¬ 
arrangement of the elements of cyanogen with those 
of water. Sclnnit and Glutz have recently observed 
that contact with strong hydrochloric acid causes 
the conversion of cyanogen into oxamide in the same 
way that it converts cane-sugar into grape-sugar. 
So likewise salicin is broken up by dilute sulphuric 
acid in the same way as by emulsin. 
The nitrogenous substance produced in the germi¬ 
nation of many cereal grains, and capable of con¬ 
verting starch into grape-sugar and dextrin, also loses 
tins property when heated to the boiling-point of 
water. Emulsin acts upon salicin and amygdalin; 
helicoidin is converted by it into salicylic acid, sali- 
genin, and sugar; arbutin into liydrocliinon and 
sugar; but emulsin does not act on starch or cane- 
sugar. Diastase acts on starch, not on amygdalin ; 
the substance in yeast-water acts upon cane-sugar, 
not on starch. A number of other substances act in 
a similar manner. Saliva acts on starch the same 
as diastase from barley; it decomposes salicin like 
emulsin into sugar and saligenin. The pancreatic 
juice contains a substance which converts starch 
into sugar, and fats into glycerin and fatty acids. 
Pepsin belongs to the same class. All these sub¬ 
stances are nitrogenous; they all possess the cha¬ 
racter of becoming inert when heated to the boiling- 
point of water, and of disappearing after a short 
time. These substances differ considerably in com¬ 
position, though the}'- act in like manner; but each 
has its own peculiar mode of action, proving that 
this takes place in different directions. 
The action of the substance contained in yeast- 
water is evidently different from that of yeast 
itself. 
None of the chemists who have investigated the 
composition of yeast have obtained concordant re¬ 
sults by analysis. Mitscherlicli found 4,7 per cent, 
carbon, Schlossberger 50 per cent.; the former 
found 10 per cent, nitrogen, the latter 12'5 per cent. 
Reichenbach found 31'57 per cent, carbon and 7'41 
nitrogen in four determinations with yeast dried at 
100° C. This yeast was very active in the moist 
state. The composition of yeast may be said to 
vary from day to day, and this is probably a sure 
sign of the change that it undergoes incessantly. 
Yeast contains sulphur as a constant consti¬ 
tuent, and it evolves sulphuretted hydrogen dur¬ 
ing putrefaction. Mitscherlicli found •6 per cent, 
sulphur. Determinations in my laboratory with dry 
