134 Green . — On Vegetable Ferments . 
coming simpler and leading to the production of C0 2 which 
always accompanies the vital processes. In the case of the 
alcoholic fermentation set up by yeast, Nageli suggests that 
the living substance of the organised yeast-cell is to be 
regarded as being in continuous and rapid molecular vibra- 
tion, and the decomposition of the fermentable substance is 
the result of the direct transference of these vibrations to the 
sugar, by means of which its equilibrium is upset and it is 
split into simpler and therefore more stable compounds 1 . 
But so great an authority as Pasteur regards alcoholic 
fermentation as indissolubly connected with the vegetative 
growth, multiplication, and metabolism of the yeast-cells. 
Sugar is so only the food-stuff out of which the organism 
obtains the material requisite for its metabolism and growth, 
the products of the fermentation being thus as it were the 
excretionary residues of the metabolised food. This is prob- 
able also from the fact that for the alcoholic fermentation to 
proceed, compounds of nitrogen must be supplied to the yeast 
as well as carbohydrate, and that the products of fermentation 
are not simply alcohol and C0 2 , but that a certain amount of 
glycerine and succinic acid are also formed. What evidence do 
we find of similar action taking place in the higher plants ? 
Lechartier and Bellamy 2 as well as Pasteur have shown that 
in certain ripe fruits alcoholic fermentation occurs. These 
exhale C0 2 in an atmosphere deprived of oxygen, sugar dis- 
appearing at the same time and alcohol being formed. The 
power of forming acids possessed by the fungus My coderma 
aceti and various bacteria is shared by the cells of succulent 
parenchyma. Though acetic acid is produced by the former 
plant from alcohol, and the parenchyma appears to form the 
acids it contains from sugar, the protoplasm in both cases 
seems to be the active agent. No enzyme can be extracted 
from the fruits alluded to which can form alcohol, any more 
than it can from yeast. The acids formed in the normal 
metabolism of the higher plants are not usually such simple 
ones as are originated by the microbes. We find malic, citric, 
1 loc. cit. 2 Comptes rendus, LXIX, 1869. 
