R74 M. H. Hoffmann on Fermentation. 
and the matter removed is examined by the microscope, the 
same spores which occur in the expressed juice of the fruit are 
recognized, mixed with impurities of all sorts ; the brown spores 
of Stemphylium and Cladosporium, and colourless fragments of 
Oidium, Monilia, Torula, &c. If the matter seraped off be placed 
in distilled water, and protected from all access of dust from 
without, there will be at the end of twenty-four hours dense 
groups of germinating filaments, and numerous cells of yeast in 
every stage of budding and fragmentation, and with all the 
varieties of form which characterize the yeast of the juices of 
fruits. Infusoria are also frequently met with. The expression 
yeast is therefore a collective denomination, and not the name of — 
a species of plant. 
2. The cells of yeast from beer or spirit in fermentation ar 
generally more similar than those of vegetable juices which have 
undergone no boiling; nevertheless they are not only round or 
oval, but also cylindrical. To ascertain what they really are, two 
methods may be adopted. The first, which has already. fre- 
quently been employed, consists in cultivating yeast, and exa- 
mining what forms of plants it gives origin to. This is the 
method employed by Kiitzing, who obtained from it some Sporo- 
tricha and a Mucor. The second, in which the yeast is pro- 
duced directly by means of the fungi which are presumed to be 
its cause, was employed by M. Bail; he made use of Ascophora 
elegans, a species of Mucor, and Penicillium glaucum; and M, 
Hoffmann states that he cannot but confirm the results obtained 
by these experiments. ‘3 
The observations of M. Hoffmann were made on a large scale 
in breweries, and on a small scale in cultivations of small por- 
tions of yeasts. In the breweries, large tufts of Penicillium 
glaucum make their appearance on the yeast which has been 
thrown out ; Penicillium breve, Corda, and Ascophora elegans, are 
also seen, but in smaller quantities. By cultivation on a small 
scale, taking all possible precautions to prevent the access of 
spores from without, M. Hoffmann has observed the deyelopment 
of the fungi above mentioned, together with Periconta hyalina. 
His experiments were made by pouring a few drops of water into. 
a test-tube inclined obliquely, placing in it a few fragments of 
fresh yeast, and stopping the mouth of the tube with wadding to 
prevent the access of any impurities from without. He soon saw 
the yeast produce mycetoid filaments. : 
To ascertain that beer-yeast is only the product of these little 
Fungi, which are so common everywhere and in all climates, 
M. Hoffmann placed in one of his tubes a solution of sugar, 
which does not ferment by itself, together with spores of Peni- 
cillium glaucum, shook the whole strongly, and then placed the 
