NATURE 
361 
THURSDAY, AUGUST 17, 1899. 
ENZYMES. 
The Soluble Ferments and Fermentation. By J. 
Reynolds Green, Sc.D., F.R.S. Pp. xiv+480. (Cam- 
bridge University Press, 1899.) 
vo igiaeae no subject in the whole of the vast 
domain of biology exceeds this in interest, and 
certainly none transcends it in the importance of its 
bearings on the doings of the human race. The bread 
and cheese we eat, the beer and wine we drink, are en- 
tirely dependent on these ferments for their preparation ; 
and the same is true of the processes of digestion which 
render their products assimilable into the plant or animal 
economy. 
Then, have not Pasteur and men who have fol- 
lowed him made clear that the principle of ferment- 
ation lies at the root of an enormous class of diseases ; 
aye, and demonstrated the truth of the doctrine by that 
most cogent of all arguments—experimental production 
of the disease from the use of the agents, and cure or 
prevention of it by the employment of the antidotes and 
therapeutic measures suggested by the scientific inquiry ? 
The making of jams, the tinning of preserved meats 
and fruits, the curing of hides and tanning of leather, and 
a hundred other branches of industry owe their suc- 
cessful pursuit to the intelligent application of the 
teachings of science ; so clearly is this being recognised 
now, that it is becoming customary to speak of “ fer- 
mentation industries” as a class. For it must no 
longer be supposed that brewing is the only fermentation 
industry ; modern discovery in connection with dyeing, 
the curing of tobacco, the retting of flax, and many 
departments of agriculture show the necessity of ex- 
tending the idea. Dr. Green’s aim has been to collect 
all that is known of the study of those remarkable and 
curious bodies (Enzymes) which can be extracted from 
the protoplasm of living cells, can be precipitated 
mechanically from the solutions, and preserved as dry, 
impalpable powders, and still retain more or less unim- 
paired their astonishing powers of again bringing about 
decompositions of sugar, fats, proteids and other 
organic substances in solutions just as they could in the 
cell itself or in the waters outside the cell. : 
These powers are astonishing, because they are mani- 
fested so extensively by almost unweighably small quan- 
tities of the enzyme, and because they are exerted so 
smoothly and with such apparent ease and economy 
on bodies which we know to be very stable, and which 
can be artificially decomposed in similar ways only by 
the application of very energetic processes and very 
wastefully. 
For it would seem that the study of fermentation is 
now the study of enzymes. Even the one sharply con- 
trasted case—alcoholic fermentation—which Pasteur’s 
classical labours appeared to place in a category apart 
from those of the enzymes, has come into line with the 
rest since Buchner’s discovery that an enzyme-like body 
can be extracted from the cells of the yeast-plant, and 
can split up sugar into alcohol and carbon dioxide out- 
side the living cell. 
NO. 1555, VOL. 60] 
Very few authors have attempted the collection of the 
huge and ever-increasing mass of information scattered 
through the various journals devoted to special rese arches 
on fermentations, and the student had long been de- 
pendent on the now antiquated books of Schutzenberger 
and Naegeli for his summary of general views on the sub. 
ject, until, in 1893, the extremely interesting but meagre 
brochure of Bourquelot came out to tantalise him with its 
disappointing sketch of recent progress. Now we can 
claim, from the hands of an English botanist, a com- 
prehensive survey, which, whatever its few faults in 
detail, covers the enormous area admirably, and brings 
out the salient points and recent discoveries in a very 
satisfactory manner. 
Until a few years ago, it was generally accepted that 
Pasteurs doctrine—fermentation is the result of life 
without oxygen—formed the corner-stone of the whole 
subject. The gradual recognition of the important parts 
played by the “soluble ferments,” or e”zymes, which, 
though their discovery dates from 1814, 1823, 1831, were 
not much studied before 1870, led to the further view 
that two categories of fermentation-processes must be 
distinguished, and the attempt was made by Naegeli and 
Sachs to uphold the idea that soluble or “unorganised ” 
ferments (enzymes) act differently from “organised” or 
living ferments—e.g. bacteria, yeast-cells, &c. 
Apart from other discrepancies, the fact that ferment- 
ations occur universally in higher plants and animals, 
as well as in lower organisms, rendered this view un- 
tenable, until the startling discovery by Buchner, in 1897, 
that a something of the nature of an enzyme can be 
extracted in water from the yeast-cell, which—outside 
the yeast-cell and quite independent of it—converts 
sugar into carbon dioxide and alcohol, may be said to 
have removed its last prop. 
Although Lafar, in his remarkably able summary of 
the ferment-activity of the lower organisms, restricts the 
definition of fermentation to “transformations of matter 
. exclusively by the vital action of ferments,” under- 
standing by the latter word the living cells themselves, 
it is evident that we are here confronted with an entirely 
different definition of fermentation. Having abandoned 
successively the views that it is a phenomenon of life 
without oxygen, that it is confined to the protoplasmic 
activity of lower organisms, that there are two different 
categories of ferments:-—organised and unorganised, we 
are now threatened once more with the generalisation 
that fermentation is a purely chemical phenomenon due 
to the peculiar molecular activity of certain bodies 
formed, it is true, by protoplasm, but acting independently 
of it: a generalisation supported by Fischer’s work on 
the constitution of the sugars, which he regards as so 
built up that an enzyme can only attack any particular 
sugar the molecular symmetry of which is related to its 
own, much as the wards of a lock can be overcome only 
by a key with a particular pattern. 
Dr. Green gives us a very exhaustive account of the 
many various enzymes now known, classifying them 
under the following heads. 
(1) Those which transform insoluble carbohydrates, 
producing soluble sugars—e.g. Diastase in germinating 
seeds and other plant-organs, which attacks starch ; 
R 
