133 
Green. — On Vegetable Ferments. 
life which are capable of setting up complex decomposition in 
various substances, and which have been known therefore as 
organised ferments. Is there anything special about these 
that warrants their being still ranked as a separate class ? 
They include a number of the lower fungi, the yeasts, and the 
great class of so-called micro-organisms or Schizophytes. The 
fermentations they set up are very varied, including the forma- 
tion of alcohol from sugar, of various forms of acids from car- 
bohydrate bodies, and the numerous products of putrefaction. 
Nageli x , in his theory of fermentation published in 1879, 
advanced reasons for considering them essentially different in 
their action from the enzymes considered in this paper, laying 
great stress on two points ; (1) that they had not yielded to any 
extracting medium any thing that could effect fermentation 
in the absence of the cells, and (2) that the products of their 
action are ‘ without exception less nutritious compounds,’ and 
that they destroy the most nutritious substances. 
We must remember in considering their action that the 
micro-organisms are for the most part unicellular plants, and 
that therefore the whole round of their metabolic processes 
takes place in the same cell : the division of labour that 
can take place in a more differentiated structure is here im- 
possible. Krukenberg 2 has shown that in the simplest forms 
the process of digestion is an intracellular one, not dependent 
on enzymes, but inherent in the protoplasm itself. Even in the 
higher forms we find a great many instances of this power of 
the protoplasm to effect chemical changes in the bodies with 
which it is supplied. In the ordinary metabolic processes of 
the vegetable cell we find it is the active agent, the chemical 
changes taking place not in the vacuoles but in the meshes of 
the protoplasmic network. Probably these are brought about 
by repeated combinations and decompositions, in which its 
own substance takes a leading part. We have evidence of 
processes of oxidation and reduction taking place there, 
leading to the appearance of various bodies ultimately be- 
1 Theorie der Gahrung, Miinchen, 1879. 
2 Krukenberg, Vergleichend-physiologische Vortrage, Heidelberg. 
