from an Agricultural and Veterinary Point of View. 55 
ing a little yeast in some water, filtering the liquid, dissolving 
in this some sugar, and then dropping carefully into it a minute 
quantity of fermenting milk, to act as the seed of the ferment 
in the limpid saccharine solution. Next day the pellucid 
fluid had become turbid, because of the active fermentation 
which had been commenced, and as the chalk dissolved, a 
deposit took place which the microscope showed was composed 
of germinating rods of the organism jnst alluded to — the lactic 
ferment. In another experiment, he substituted for the yeast- 
water a clear decoction of nitrogenous matter, but the ferment 
invariably appeared in the same manner. 
In order to effectually silence the partisans of Liebig's theory, 
and indeed of all chemists, as to the accidental presence of the 
organised ferment, the cells of which, they asserted, perished 
during fermentation and formed lactate of ammonia, Pasteur 
unremittingly laboured to demonstrate the falsity of the theory, 
and to prove that not only was there no ammonia formed during 
alcoholic fermentation, but if it were added it disappeared, 
entering into the formation of the new cells. Two notable 
characteristic and crucial experiments he made, which finally 
settled the dispute. One was with regard to the yeast of beer 
or alcohol, and the other to the lactic ferment. He introduced 
into a pure solution of sugar a small quantity of a crystalline 
salt of ammonia, and some phosphates of potash and magnesia ; 
into this mixture, which, it will be observed, was destitute of 
albuminoid matter, he sowed an imponderable quantity of 
yeast — the living cells of the lactic fermentation. The cells 
thus sown germinated and multiplied, the sugar fermented, and 
the phosphorus, magnesium, and potassium of the salts united 
with elements of the sugar of milk, and were in the end con- 
verted into lactic acid. A second experiment made with the 
same skill and care yielded the same results, and demolished 
the theory of Berzelius and Liebig, which had no longer any 
foundation. The whole process took place between the sugar 
aud the ferment germ — a living organism — which owed its 
growth and multiplication to the nutriment it found in the 
sugar : fermentation, in short, was simply a phenomenon of 
nutrition, the ferment contriving to grow upon the sugar and 
the mineral salts, the remaining portions of these combining to 
form, in fermenting milk, alcohol and lactic acid, and in the 
saccharine fermentation alcohol and acetic acid. 
The results of his experiments, and the conclusions he arrived 
at from a consideration of them, Pasteur laid before the Academy 
of Sciences in 1857. 
By the light of his discovery of the lactic ferment, Pasteur soon 
found a new ferment — the butyric, which has its own special 
fermentation, resulting in the production of butyric acid. This 
