1 3 6 The Australasian Scientific Magazine. [Nov. i, 1S85. 
Van Helmont (1648) studied the gases given off. Silvius de 
la Boe (1659) showed that the effervescence arising from the action of an 
acid on an alkaline carbonate, as in the familiar seidlitz powder, was of a 
different character from that arising from fermentation, and Becker ( 1 682} 
established the fact that saccharine liquids alone are capable of entering 
into spirituous fermentation. Stahl, the celebrated originator of the phlogi- 
ston theory (1697), supposed that a ferment was a body endued with a 
motion which it transmitted to the fermentable matter ; but from his time 
to that of Lavoisier the whole subject received but little attention. The 
great impulse given to chemistry by the many important discoveries at the 
end of last century, and the remodelling of the science by Lavoisier and 
his collaborateurs, placed, among other phenomena, the study of fermenta- 
tion on a fresh footing. Lavoisier himself devoted time to it, and he was 
the first to trace the connection between sugar and the derivatives from it 
which fermentation produces. But while from this time onwards definite 
progress was made in our knowledge of the various chemical changes in 
processes of fermentation, the nature of ferments — the exciting causes of 
fermentation — remained unknown. The balance and the measure enabled 
the changes to be followed, but what set it]) the changes remained as much 
a mystery as to the old alchemists. Light upon this subject came, how- 
ever, in a totally different channel. As far back as 1680 Leuwenhoeck 
had examined beer yeast with the microscope, and noticed “ovoid 
globules,” but he could not determine their nature. Kabroni, in 1787, 
went a step further, and concluded that “the matter which de- 
composes sugar is a vegeto-animal substance.” Thenard, Gay-Lussac, 
Colin, Destnazieres, and many others of less note puzzled themselves 
with the same problem, but without any real advance. Mean- 
while, the microscope as an instrument was constantly receiving improve 
ments, and, in 1835, in the hands of that accomplished philosopher, 
renowned in so many branches of science, Cagniard de Latour, it revealed 
that yeast is “amass of organic globules reproducing themselves by 
buds,” and it therefore appeared to him clearly to belong to the vegetable 
kingdom. The observation of this budding came as a wonder. It ex- 
cited much attention, and soon the examination of yeast by Schwann, 
Kiitzing, Quevenne, Misterlich, Turpin and others gave corroborative 
testimony, and in the course of a few years the “ yeast plant ” came to 
be spoken of popularly. The present generation is so familiar with the 
name that it is difficult to realise that a little over forty years ago its 
nature was unknown. As the number of low forms of life that were 
microscopically examined was extended much discussion arose as to what 
were animal and what vegetable. The volvox g/ol>ator, among other 
forms, has been so bandied about from zoologist to botanist, and from 
botanist to zoologist, that hardly anyone can have escaped hearing about 
it. Scientific football it has been even derisively named. The 
yeast plant, however, has continued to be recognised as a plant. 
Its discovery, though, by no means cleared up [all at once the 
mysteries of the fermentation it produces, and a fuli conception 
of the molecular changes that take place is not yet gained. But 
even the explanation in its broader outlines, now accepted as correct, was 
not received without severe fighting. The mighty Liebig thundered against 
it, though a few years before his death he made what was tantamount to a 
retraction of his views. The establishment of the fact that the yeast plant 
didin some way produce fermentation, even though dimly understood, led 
