IC-NRLF
&
Mwdlrr.
ERKELEY
LIBRARY
UNIVERSITY Of
CALlFORNiA
ORGANIC CHEMISTRY
IN ITS APPLICATIONS
AGRICULTURE AND PHYSIOLOGY,
JUSTUS LIEBIG, M.D., PH.D., F.R.S., M.R.I.A.,
PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF OIESSEN \ KNIGHT OF THE HESSIAN ORDER;
MEMBER OF THE ROYAL ACADEMY OF SCIENCES OF STOCKHOLM; CORKESPONDING
MEMBER OF THE ROYAL ACADEMIES OF SCIENCES OF BERLIN AND
MUNICH ; OF THE IMPERIAL ACADEMY OF ST. PETKRS-
BURGH ; OF THE ROYAL INSTITUTION OF
AMSTERDAM, ETC. ETC.
EDITED FROM THE MANUSCRIPT OF THE AUTHOR
BY LYON PLAYFAIR, PH.D.
LONDON :
PRINTED FOR TAYLOR AND WALTON,
BOOKSELLERS AND PUBLISHERS TO UNIVERSITY COLLEGE,
UPPER GOWER STREET.
MDCCCXL.
LONDON :
BRADBURY AND EVANS, PRINTERS, WHTTEFRIAKS.
LOAN STACK
THE BEIT1SH ASSOCIATION
FOR THE
ADVANCEMENT OF SCIENCE.
ONE of the most remarkable features of modern
times is the combination of large numbers of indi-
viduals representing the whole intelligence of
nations, for the express purpose of advancing
science by their united efforts, of learning its pro-
gress, and of communicating new discoveries.
The formation of such associations is, in itself, an
evidence that they were needed.
It is not every one who is^called by his situation
in life to assist in extending the bounds of
science; but all mankind have a claim to the
blessings and benefits which accrue from its
earnest cultivation. The foundation of scientific
institutions is an acknowledgment of these bene-
vi PREFACE.
fits, and this acknowledgment proceeding from
whole nations may be considered as the triumph
of mind over empiricism.
Innumerable are the aids afforded to the means
of life, to manufactures and to commerce, by the
truths which assiduous and active inquirers have
discovered and rendered capable of practical
application. But it is not the mere practical
utility of these truths which is of importance.
Their influence upon mental culture is most bene-
ficial ; and the new views acquired by the know-
ledge of them enable the mind to recognise, in the
phenomena of nature, proofs of an infinite wisdom,
for the unfathomable profundity of which, lan-
guage has no expression.
At one of the meetings of the chemical section
of the " British Association for the Advancement
of Science," the honourable task of preparing a
report upon the state of organic chemistry was
imposed upon me. In the present work I present
the Association with a part of this report.
I have endeavoured to develop, in a manner
correspondent to the present state of science, the
fundamental principles of chemistry in general,
PREFACE. Vll
and the laws of organic chemistry in particular, in
their applications to agriculture and physiology ;
to the causes of fermentation, decay, and putre-
faction ; to the vinous and acetous fermentations,
and to nitrification. The conversion of woody
fibre into wood- and mineral-coal, the nature of
poisons, contagions and miasms, and the causes
of their action on the living organism, have been
elucidated in their chemical relations.
I shall be happy if I succeed in attracting the
attention of men of science to subjects which so
so well merit to engage their talents and energies,
perfect agriculture is the true foundation of all
trade and industry — it is the foundation of the
riches of states. But a rational system of agri-
culture cannot be formed without the application
of scientific principles; for such a system must
be based on an exact acquaintance with the
means of nutrition of vegetables, and with the
influence of soils and action of manure upon
them. This knowledge we must seek from che-
mistry, which teaches the mode of investigating
the composition and of studying the characters of
the different substances from which plants derive
their nourishment.
Vlll PREFACE.
The chemical forces play a part in all the pro-
cesses of the living animal organism; and a
number of transformations and changes in the
living body are exclusively dependent on their
influence. The diseases incident to the period of
growth of man, contagion and contagious matters,
have their analogues in many chemical processes.
The investigation of the chemical connexion
subsisting between those actions proceeding in the
living body, and the transformations presented by
chemical compounds, has also been a subject of
my inquiries. A perfect exhaustion of this sub-
ject, so highly important to medicine, cannot be
expected without the co-operation of physiologists.
Hence I have merely brought forward the purely
chemical part of the inquiry, and hope to attract
attention to the subject.
Since the time of the immortal author of the
" Agricultural Chemistry," no chemist has occu-
pied himself in studying the applications of che-
mical principles to the growth of vegetables, and
to organic processes. I have endeavoured to
follow the path marked out by Sir Humphry
Davy, who based his conclusions only on that
which was capable of inquiry and proof. This is
PREFACE. IX
the path of true philosophical inquiry, which pro-
mises to lead us to truth — the proper object of
our research.
In presenting this'report to the British Associa-
tion I feel myself bound to convey my sincere
thanks to Dr. Lyon Playfair, of St. Andrews, for
the active assistance which has been afforded me in
its preparation by that intelligent young chemist
during his residence in Giessen. I cannot suppress
the wish that he may succeed in being as useful,
by his profound and well-grounded knowledge of
chemistry, as his talents promise.
DR. JUSTUS LIEBIG.
Giessen, September 1, 1840.
CONTENTS.
PART I.
THE CHEMICAL PROCESSES IN THE NUTRITION OF
VEGETABLES.
Page
Subject of the Work . . . . . 1
The Constituent Elements of Plants . . .2
The Assimilation of Carbon . . . .4
Composition and Properties of Humus . . 5
Absorption of Humus ..... 9
Fertility of different Soils . . . . . 13
Influence of Manure . . . . .15
Proportion of Carbonic Acid in the Atmosphere . 17
The Atmosphere is the source of Carbon in Plants . 19
Influence of the Shade on Plants . . 27
Exhalation of Oxygen by Plants . . . .33
Neglect of Chemistry by Botanists . . 35
Object of Experiments in Physiology . . .37
Conditions essential to Nutrition . 39
Xll CONTENTS.
Page
On the Origin and Action of Humus . . .45
Growth of Plants . . . . . . 49
Transformations of Organic Substances . . 51
Nature of Organic Chemical Processes . 53
The use of Humus explained . . 59
Humus is not indispensable for Plants . . 61
Assimilation of Hydrogen . . . .63
Hydrogen is obtained by the Decomposition of Water . 65
Its assimilation is attended with the Evolution of Oxygen . 67
On the Origin and Assimilation of Nitrogen . 69
Source of Nitrogen in Plants . . . - 70
Ammonia is always contained in the Atmosphere . . 73
Use of Gypsum in manuring Meadow Land . . 87
Use of burned Clay as Manure . . 89
The Inorganic Constituents of Plants . . .92
Plants contain an invariable quantity of Alkaline 'Bases . 94
The origin of common Salt in Plants . . .114
The Art of Culture . . . . . 116
Use of Humus . . . . . 1 18
Nutrition and Growth of Plants . . . . 1 23
Necessity of Azotised Substances . . .131
Influence of the Food on the Produce . 133
Composition of Soils . . . . .141
The Fertility of Soils . . . . 145
Fallow— Crops . . . . . . J57
The Interchange of Crops and Manure . 159
Manure . .174
CONTENTS. xiii
Page
Composition of Animal Manures . . . 175
The essential Elements of Manure . . .179
Bone Manure . . . . . . 185
Manure supplies Nitrogen . . . .189
Mode of applying Urine . . . . 193
Value of human Excrements . . . .197
Concluding Remarks . . . . . 201
APPENDIX TO PART I.
Growth of Plants without Mould . . 204
On the Action of Charcoal on Vegetation . . -207
On the Rotation of Crops at Bingen, on the Rhine . 211
On a mode of manuring Vines . . 211
PART II.
THE CHEMICAL PROCESSES OF FERMENTATION, DECAY,
AND PUTREFACTION.
Chemical Transformations . . . .217
Their Cause . . . . . . . 220
Chemical Transformations of Organic Compounds . 231
Transformations of Bodies containing Nitrogen . . 240
Fermentation of Sugar ..... 248
Yeast or Ferment, . . . . . . 251
Nature of Fermentation . . . . .257
i89 or Decay . . . • • 260
XIV CONTENTS.
Page
Nature of the Process . . . . . 263
Nitrification . . . . . . . 276
Vinous Fermentation : — Wine and Beer . . 282
Various Properties of Wines . . . . . 293
Fermentation of Beer — the Bavarian Process . • 295
Decay of Woody Fibre . . . > . 308
Vegetable Mould . . . . .315
On the Mouldering of Bodies . . . . . 317
Paper . ... 318
Brown Coal . . . . ' . . . 321
Mineral Coal . . . . .327
On Poisons, Contagious Matter , and Miasms . . 329
Inorganic Poisons ..... 330
Organic Poisons . . . . . . 343
Putrid Poisons . . . . . .347
%
Morbid Poisons , . . . . . 351
Mode of Action of Contagions and Miasms . 355
Addition to Note at Page 17 .... 385
Tables showing the Proportion between the Hessian and
English Standard of Weights and Measures . . 386
ERRATA.
Page 10 line 18 for essian . . . read Hessian. t/~"
— 64 — 6 for 8 cwt. . . read 10 cwt.
— 92—10 from bottom, for are formed, read are found.
— 103 — 16 for nitrate of abrontian . read nitrate of strontia.
— 126 — 1 and 2, for 476/fo. and 37/fo. read 47 bolls, and 37 bolls.
— 183 — 10 for (10 Si Oz+ KO. .) . read (10 Si O3 + KO.)
— 251 — 3 for laclate acid . . read lactic acid.
— 265 — 8 from bottom, for oxyen . read oxygen.
ORGANIC CHEMISTRY
APPLIED TO
PART I.
OF THE CHEMICAL PROCESSES IN THE NUTRITION OF
VEGETABLES.
THE object of organic chemistry is to discover
the chemical conditions which are essential to the
life and perfect development of animals and vege-
tables, and, generally, to investigate all those pro-
cesses of organic nature which are due to the
operation of chemical laws.
The continued existence of all living beings is
dependent on the reception by them of certain
substances, which are applied to the nutrition of
their frame. An inquiry, therefore, into the condi-
tions on which the life and growth of living beings
depend, involves the study of those substances
which serve them as nutriment, as well as the
investigation of the sources whence these sub-
stances are derived, and the changes which they
undergo in the process of assimilation.
The primary source whence man and animals
B
2 OF THE CONSTITUENT ELEMENTS
derive the means of their growth and support is
the vegetable kingdom.
Plants, on the other hand, find new nutritive
material only in inorganic substances.
The purport of this work is to elucidate the
chemical processes engaged in the nutrition of
vegetables.
The first part of it will be devoted to the exami-
nation of the matters which supply the nutriment
of plants, and of the changes which these matters
undergo in the living organism. The chemical
compounds which afford to plants their principal
constituents, viz., carbon and nitrogen, will here
come under consideration, as well as the relations
in which the vital functions of vegetables stand to
those of the animal economy and to other pheno-
mena of nature.
The second part of the work will treat of the
chemical processes which effect the complete
destruction of plants and animals after death, such
as the peculiar modes of decomposition, usually
described as fermentation, putrefaction, and decay ;
and in this part the changes which organic sub-
stances undergo in their conversion into inorganic
compounds, as well as the causes which determine
these changes, will become matter of inquiry.
OF THE CONSTITUENT ELEMENTS OF PLANTS.
Carbon enters into the composition of all plants,
and of all their different parts or organs.
OF PLANTS. 3
The substances which constitute the principal
mass of every vegetable are compounds of carbon
with oxygen and hydrogen in the proper relative
proportions for forming water. Woody fibre,
starch, sugar, and gum, for example, are such com-
pounds of carbon with the elements of water. In
another class of substances containing carbon as an
element, oxygen and hydrogen are again present ;
but the proportion of oxygen is greater than would
be required for producing water by union with
the hydrogen. The numerous organic acids met
with in plants belong, with few exceptions, to this
class.
A third class of vegetable compounds contain
carbon and hydrogen, but no oxygen, or less of
that element than would be required to convert all
the hydrogen into water. These may be regarded
as compounds of carbon with the elements of
water and an excess of hydrogen. Such are the
volatile and fixed oils, wax, and the resins. Many
of them have acid characters.
The juices of all vegetables contain organic acids,
generally combined with the inorganic bases, or
metallic oxides ; for these metallic oxides exist in
every plant, and may be detected in its ashes after
incineration.
Nitrogen is an element of vegetable albumen and
gluten ; it is a constituent of the acids, and of what
are termed the " indifferent substances," of plants,
as well as of those peculiar vegetable compounds
OF THE ASSIMILATION OF CARBON.
which possess all the properties of metallic oxides,
and are known as " organic bases."
Estimated by its proportional weight, nitrogen
forms only a very small part of plants, but it is
never entirely absent from any part of them. Even
when it does not absolutely enter into the compo-
sition of a particular part or organ, it is always to
be found in the fluids which pervade it.
It follows from the facts thus far detailed, that
the development of a plant requires the presence,
first, of substances containing carbon and nitrogen,
and capable of yielding these elements to the grow-
ing organism ; secondly, of water and its elements ;
and lastly, of a soil to furnish the inorganic matters
which are likewise essential to vegetable life.
OF THE ASSIMILATION OF CARBON.
The fertility of every soil is generally supposed
by vegetable physiologists to depend on the presence
in it of a peculiar substance to which they have
given the name of humus. This substance, believed
to be the principal nutriment of plants, and to be
extracted by them from the soil in which they
grow, is itself the product of the decay of other
plants.
Humus is described by chemists as a brown
substance, easily soluble in alkalies, but only
slightly soluble in water, and produced during
the decomposition of vegetable matters by the
action of acids or alkalies. It has, however,
COMPOSITION OF HUMUS. 5
received various names according to the different
external characters and chemical properties which
it presents. Thus, ulmin, humic acid, coal of
humus, and humin, are names applied to modifica-
tions of humus. They are obtained by treating
peat, woody fibre, soot, or brown coal with alkalies ;
by decomposing sugar, starch, or sugar-of-milk
by means of acids ; or by exposing alkaline solu-
tions of tannic and gallic acids to the action of
the air.
The modifications of humus which are soluble
in alkalies, are called humic acid ; while those
which are insoluble have received the designations
of humin and coal of humus.
The names given to these substances might cause
it to be supposed that their composition is identical.
But a more erroneous notion could not be enter-
tained ; since even sugar, acetic acid, and colophan
do not differ more widely in the proportions of
their constituent elements, than do the various
modifications of humus.
Humic acid formed by the action of hydrate of
potash upon sawdust contains, according to the ac-
curate analysis of Peligot, 72 per cent, of carbon,
while the humic acid obtained from turf and brown
coal contains, according to Sprengel, only 58 per
cent.; that produced by the action of dilute sulphuric
acid upon sugar, 57 per cent, according to Malaguti ;
and that, lastly, which is obtained from sugar or from
starch, by means of muriatic acid, according to the
6 OF THE ASSIMILATION OF CARBON.
analysis of Stein, 64 per cent. All these analyses
have been repeated with care and accuracy, and the
proportion of carbon in the respective cases has been
found to agree with the estimates of the different
chemists above mentioned ; so that there is no rea-
son to ascribe the difference in this respect between
the varieties of humus to the mere difference in the
methods of analysis or degrees of expertness of the
operators. Malaguti states, moreover, that humic
acid contains an equal number of equivalents of
oxygen and hydrogen, that is to say, that these ele-
ments exist in it in the proportions for forming
water ; while, according to Sprengel, the oxygen is
in excess, and Peligot even estimates the quantity
of oxygen at 1 4 equivalents, and the hydrogen at
only 6 equivalents, making the deficiency of hydro-
gen as great as 8 equivalents.
It is quite evident, therefore, that chemists have
been in the habit of designating all products of the
decomposition of organic bodies which had a brown
or brownish-black colour by the names of humic
acid or humin, according as they were soluble or
insoluble in alkalies; although in their composi-
tion and mode of origin, the substances thus con-
founded might be in no way allied.
Not the slightest ground exists for the belief that
one or other of these artificial products of the de-
composition of vegetable matters exists in nature
in the form and endowed with the properties of the
vegetable constituents of mould ; there is not the
PROPERTIES OF HUMUS. /
shadow of a proof that one of them exerts any influ-
ence on the growth of plants either in the way of
nourishment or otherwise.
Vegetable physiologists have, without any appa-
rent reason, imputed the known properties of the
humus and humic acids of chemists to that consti-
tuent of mould which has received the same name,
and in this way have been led to their theoretical
notions respecting the functions of the latter sub-
stance in vegetation.
The opinion that the substance called humus is
extracted from the soil by the roots of plants, and
that the carbon entering into its composition serves
in some form or other to nourish their tissues, is so
general and so firmly established, that hitherto any
new argument in its favour has been considered
unnecessary ; the obvious difference in the growth
of plants according to the known abundance or
scarcity of humus in the soil, seemed to afford in-
contestable proof of its correctness.
Yet, this position, when submitted to a strict ex-
amination, is found to be untenable, and it becomes
evident from most conclusive proofs that humus in
the form in which it exists in the soil does not yield
the smallest nourishment to plants.
The adherence to the above incorrect opinion
has hitherto rendered it impossible for the true
theory of the nutritive process in vegetables to
become known, and has thus deprived us of our
best guide to a rational practice in agriculture.
8 OF THE ASSIMILATION OF CARBON.
Any great improvement in that most important of
all arts is inconceivable without a deeper and more
perfect acquaintance with the substances which
nourish plants, and with the sources whence they
are derived ; and no other cause can be discovered
to account for the fluctuating and uncertain state
of our knowledge on this subject up to the present
time, than that modern physiology has not kept
pace with the rapid progress of chemistry.
In the following inquiry we shall suppose the
humus of vegetable physiologists to be really en-
dowed with the properties recognised by chemists
in the brownish black deposits which they obtain
by precipitating an alkaline decoction of mould
or peat by means of acids, and which they name
humic acid.
Humic acid, when first precipitated, is a floccu-
lent substance, is soluble in 2500 times its weight
of water, and combines with alkalies, lime and mag-
nesia, forming compounds of the same degree of
solubility. (Sprengel.)
Vegetable physiologists agree in the supposition
that by the aid of water humus is rendered capable
of being absorbed by the roots of plants. But ac-
cording to the observation of chemists, humic acid
is soluble only when newly precipitated, and be-
comes completely insoluble when dried in the ah*,
or when exposed in the moist state to the freezing
temperature. (Sprengel.)
Both the cold of winter and the heat of summer
ABSORPTION OF HUMUS. 9
therefore are destructive of the solubility of humic
acid, and at the same time of its capability of being
assimilated by plants. So that, if it is absorbed by
plants, it must be in some altered form.
The correctness of these observations is easily
demonstrated by treating a portion of good mould
with cold water. The fluid remains colourless,
and is found to have dissolved less than 100,000
part of its weight of organic matters, and to
contain merely the salts which are present in rain-
water.
Decayed oak-wood, likewise, of which humic acid
is the principal constituent, was found by Berzelius
to yield to cold water only slight traces of soluble
materials; and I have myself verified this observa-
tion on the decayed wood of beech and fir.
These facts, which show that humic acid in its
unaltered condition cannot serve for the nourish-
ment of plants, have not escaped the notice of phy-
siologists ; and hence they have assumed that the
lime or the different alkalies found in the ashes of
vegetables render soluble the humic acid and fit it
for the process of assimilation.
Alkalies and alkaline earths do exist in the dif-
ferent kinds of soil in sufficient quantity to form
such soluble compounds with the humic acid.
Now, let us suppose that humic acid is absorbed
by plants in the form of that salt which contains
the largest proportion of humic acid, namely, in the
form of humate of lime, and then from the known
10 OF THE ASSIMILATION OF CARBON.
quantity of the alkaline bases contained in the
ashes of plants, let us calculate the amount of hu-
mic acid which might be assimilated in this man-
ner. Let us admit, likewise, that potash, soda, and
the oxides of iron and manganese have the same
capacity of saturation as lime with respect to hu-
mic acid, and then we may take as the basis of our
calculation the analysis of M. Berthier, who found
that 1000 Ibs. of dry fir- wood yielded 4 Ibs. of
ashes, and that in every 100 Ibs. of these ashes,
after the chloride of potassium and sulphate of
potash were extracted, 53 Ibs. consisted of the basic
metallic oxides, potash, soda, lime, magnesia, iron,
and manganese.
40,000 square feet* Hessian measure of wood-
land yield annually, according to Dr. Heyer, on an
average, 2650 Ibs. Hessian of dry fir- wood, which
contain 5*6 Ibs. I \ essian of metallic oxides.
Now, according to the estimates of Malaguti and
Sprengel, 1 Ib. Hessian of lime combines chemically
with 10*9 Ibs. Hessian of humic acid; 5 '6 Ibs. of
the metallic oxides would accordingly introduce
into the trees 61 Ibs. Hessian of humic acid, which,
admitting humic acid to contain 58 per cent, of
carbon, would correspond to 91 Ibs. Hessian of
dry wood. But we have seen that 2650 Ibs. of fir-
wood are really produced.
* [The numbers in the text in Hessian feet and pounds will show
a proportion to other numbers equally well as if they were reduced to
their equivalents in English. For those, however, who prefer knowing
the exact English quantities, a table of equivalents is given at the end.]
ABSORPTION OF HUMUS. 11
Again, if the quantity of humic acid which might
be introduced into wheat in the form of humates is
calculated from the known proportion of metallic
oxides existing in wheat straw, (the sulphates and
chlorides also contained in the ashes of the straw
not being included,) it will be found that the wheat
growing on 40,000 square feet of land would receive
in that way 57i Ibs. Hessian of humic acid, cor-
responding to 85 Ibs. Hessian of woody fibre. But
the extent of land just mentioned produces, in-
dependently of the roots and grain, 1780 Ibs.
Hessian of straw, the composition of which is the
same as that of woody fibre.
It has been taken for granted in these calcula-
tions that the basic metallic oxides which have
served to introduce humic acid into the plants do
not return to the soil, since it is certain that they
remain fixed in the parts newly formed during the
process of growth.
Let us now calculate the quantity of humic acid
which plants can receive under the most favour-
able circumstances, viz. through the agency of
rain-water.
The quantity of rain which falls at Erfurt, one
of the most fertile districts of Germany, during the
months of April, May, June, and July, is stated
by Schubler to be \7\ Ibs. Hessian over every
square foot of surface ; 40,000 square feet con-
sequently receive 700,000 Ibs. Hessian of rain-
water.
12 OF THE ASSIMILATION OF CARBON.
If, now, we suppose that the whole quantity of
this rain is taken up by the roots of a summer plant
which ripens four months after it is planted, so that
not a pound of this water evaporates except from
the leaves of the plant ; and if we further assume
that the water thus absorbed is saturated with hu-
mate of lime (the most soluble of the humates, and
that which contains the largest proportion of humic
acid); then the plants thus nourished would not
receive more than 300 Ibs. Hessian of humic acid,
since one part of humate of lime requires 2500
parts of water for solution.
But the extent of land which we have mentioned
produces 2580 Ibs. Hessian of corn (in grain and
straw, the roots not included), or 20,000 Ibs. Hes-
sian of beet-root (without the leaves and small
radicle fibres). It is quite evident that the 300
Ibs. of humic acid, supposed to be absorbed, cannot
account for the quantity of carbon contained in
the roots and leaves alone, even if the supposition
were correct, that the whole of the rain-water was
absorbed by the plants. But since it is known
that only a small portion of the rain-water which
falls upon the surface of the earth evaporates
through plants, the quantity of carbon which can
be conveyed into them in any conceivable manner
by means of humic acid must be extremely trifling
in comparison with that actually produced in vege-
tation.
Other considerations, of a higher nature, confute
FERTILITY OF DIFFERENT SOILS. 13
the common view respecting the nutritive office of
humic acid, in a manner so clear and conclusive
that it is difficult to conceive how it could have
been so generally adopted.
Fertile land produces carbon in the form of
wood, hay, grain, and other kinds of growth,
the masses of which differ in a remarkable
degree.
2650 Ibs. Hessian of firs, pines, beeches, &c. grow
as wood upon 40,000 square feet of forest-land with
an average soil. The same superficies yields 2500
Ibs. Hessian of hay.
A similar surface of corn-land gives from 18,000
to 20,000 Ibs. Hessian of beet-root, or 800 Ibs.
Hessian of rye, and 1780 Ibs. Hessian of straw,
160 sheaves of 14 Ibs. Hessian each, in all, 2580
Ibs. Hessian.
One hundred parts of dry fir-wood contain 38
parts of carbon ; therefore, 2650 Ibs. contain 1007
Ibs. Hessian of carbon.
One hundred parts of hay*, dried in .air, contain
44*31 parts carbon. Accordingly, 2500 Ibs. of hay
contain 1008 Ibs. Hessian of carbon.
Beet-roots contain from 89 to 89*5 parts water,
and from 10*5 to 11 parts solid matter, which
consists of from 8 to 9 per cent, sugar, and from 2
* 100 parts of hay, dried at 100° C. (212° F.) and burned with oxide
of copper in a stream of oxygen gas, yielded 51-93 water, 165'8 carbonic
acid, and 6'82 of ashes. This gives 45-87 carbon, 5-76 hydrogen,
31-55 oxygen, and 6'82 ashes. Hay, dried in the air, loses 1 1-2 p. c.
water at 100° C. (212 F.}.—Dr. Will.
14 OF THE ASSIMILATION OF CARBON.
to 2^ per cent, cellular tissue. Sugar contains 42'4
per cent. ; cellular tissue, 47 per cent, of carbon.
20,000 Ibs. of beet-root, therefore, if they con-
tained 9 per cent, of sugar, and 2 per cent, of
cellular tissue, would yield 936 Ibs. Hessian of
carbon, of which 756 Ibs. Hessian would be due
to the sugar, and 180 Ibs. Hessian to the cellular
tissue ; the carbon of the leaves and small roots
not being included in the calculation.
One hundred parts of straw *, dried in air, con-
tain 38 per cent, of carbon; therefore 1780 Ibs. of
straw contain 676 Ibs. Hessian of carbon. One
hundred parts of corn contain 43 parts of carbon ;
800 Ibs. must therefore contain 344 Ibs. Hessian;—
in all, 1020 Ibs. Hessian of carbon.
40,000 square feet of wood and meadow land
produce, consequently, 1007 Ibs. of carbon; while
the same extent of arable land yields in beet-root,
without leaves, 936 Ibs. ; or in corn, 1020 Ibs.
It must be concluded from these incontestable
facts, that equal surfaces of cultivated land of an
average fertility produce equal quantities of car-
bon ; yet, how unlike have been the different
conditions of the growth of the plants from which
this has been deduced !
Let us now inquire whence the grass in a meadow,
* Straw analysed in the same manner, and dried at 100° C., gave
46-37 p. c. of carbon, 5'G8 p. c. of hydrogen, 43*93 p. c. of oxygen, and
4-02 p. c. of ashes. Straw dried in the air at 100° C. lost 18 p. c. of
water.— Dr. Will.
INFLUENCE OF MANURE. 15
or the wood in a forest receives its carbon, since
there no manure — no carbon — has been given to it
as nourishment ? and how it happens, that the soil,
thus exhausted, instead of becoming poorer, becomes
every year richer in this element ?
A certain quantity of carbon is taken every
year from the forest or meadow, in the form of
wood or hay, and, in spite of this, the quantity of
carbon in the soil augments ; it becomes richer in
humus.
It is said, that in fields and orchards all the carbon
which may have been taken away as herbs, as
straw, as seeds, or as fruit, is replaced by means of
manure ; and yet this soil produces no more carbon
than that of the forest or meadow where it is never
replaced. It cannot be conceived that the laws
for the nutrition of plants are changed by culture, —
that the sources of carbon for fruit or grain, and
for grass or trees, are different.
It is not denied that manure exercises an influ-
ence upon the development of plants ; but it may
be affirmed with positive certainty, that it neither
serves for the production of the carbon, nor has
any influence upon it, because we find that the
quantity of carbon produced by manured lands is
not greater than that yielded by lands which are
not manured. The discussion as to the manner in
which manure acts has nothing to do with the
present question, which is, the origin of the carbon.
The carbon must be derived from other sources ;
16 OF THE ASSIMILATION OF CARBON.
and as the soil does not yield it, it can only be
extracted from the atmosphere.
In attempting to explain the origin of carbon in
plants, it has never been considered that the ques-
tion is intimately connected with that of the origin
of humus. It is universally admitted that humus
arises from the decay of plants. No primitive
humus, therefore, can have existed ; for plants
must have preceded the humus.
Now, whence did the first vegetables derive their
carbon ? and in what form is the carbon contained
in the atmosphere ?
These two questions involve the consideration of
two most remarkable natural phenomena, which,
by their reciprocal and uninterrupted influence,
maintain the life of the individual animals and
vegetables, and the continued existence of both
kingdoms of organic nature.
One of these questions is connected with the in-
variable condition of the air with respect to oxygen.
One hundred volumes of air have been found, at
every period and in every climate, to contain 21
volumes of oxygen, with such small deviations, that
they must be ascribed to errors of observation.
Although the absolute quantity of oxygen con-
tained in the atmosphere appears very great when
represented by numbers, yet it is not inexhaustible.
One man consumes by respiration 45* Hessian cubic
* [For the proportions in English weights and measures see the table
at the end of the volume ]
ITS PROPORTION IN THE ATMOSPHERE. 17
feet of oxygen in 24 hours; 10 centners of charcoal
consume 58,112 cubic feet of oxygen during its
combustion ; and a small town like Giessen (with
about 7000 inhabitants) extracts yearly from the
air, by the wood employed as fuel, more than 1000
millions of cubic feet of this gas.
When we consider facts such as these, our
former statement, that the quantity of oxygen in
the atmosphere does not diminish in the course
of ages*, — that the air at the present day, for
example, does not contain less oxygen than that
found in jars buried for 1800 years in Pompeii,
— appears quite incomprehensible, unless some
source exists whence the oxygen abstracted is
replaced. How does it happen, then, that the
proportion of oxygen in the atmosphere is thus
invariable ?
The answer to this question depends upon an-
other ; namely, what becomes of the carbonic acid,
which is produced during the respiration of animals,
and by the process of combustion ? A cubic foot
of oxygen gas, by uniting with carbon so as to form
* The air contains, in maxima, TcyBfss carbonic acid gas and
oxygen gas. A man consumes, in one year, 166,075 cubic feet of oxygen
gas (or 45,000 cubic inches in one day, according to Lavoisier, Seguin,
and Dary); a thousand million men must accordingly consume 166
billion cubic feet in one year ; this is equal to y^ of the quantity
which is contained in the air in the form of carbonic acid. The
carbonic acid in the air would thus be doubled in 1000 years,
and man alone would exhaust all the oxygen, and convert it into car-
bonic acid in 303 times as many years. The consumption by animals,
and by the process of combustion, is not introduced into the calcula-
tion.
C
18 OF THE ASSIMILATION OF CARBON.
carbonic acid, does not change its volume. The
billions of cubic feet of oxygen extracted from the
atmosphere, produce the same number of billions
of cubic feet of carbonic acid, which immediately
supply its place.
The most exact and most recent experiments of
De Saussure, made in every season, for a space of
three years, have shown, that the air contains on an
average 0.000415 of its own volume of carbonic
acid gas ; so that, allowing for the inaccuracies of
the experiments, which must diminish the quantity
obtained, the proportion of carbonic acid in the
atmosphere may be regarded as nearly equal to
1-1000 part of its weight. The quantity varies
according to the seasons ; but the yearly average
remains continually the same.
We have no reason to believe that this propor-
tion was less in past ages ; and nevertheless, the
immense masses of carbonic acid, which annually
flow into the atmosphere from so many causes,
ought perceptibly to increase its quantity from year
to year. But we find, that all earlier observers
describe its volume as from one-half to ten times
greater than that which it has at the present time ;
so that we can hence at most conclude, that it has
diminished.
It is quite evident, that the quantities of carbonic
acid and oxygen in the atmosphere, which remain
unchanged by lapse of time, must stand in some
fixed relation to one another ; a cause must exist
ITS SOURCE, THE ATMOSPHERE. 19
which prevents the increase of carbonic acid, by
removing that which is constantly forming ; and
there must be some means of replacing the oxygen,
which is removed from the air by the processes of
combustion and putrefaction, as well as by the
respiration of animals.
Both these causes are united in the process of
vegetable life.
The facts which we have stated in the preceding
pages prove, that the carbon of plants must be de-
rived exclusively from the atmosphere. Now, car-
bon exists in the atmosphere only in the form of
carbonic acid ; and, therefore, in a state of com-
bination with oxygen.
It has been already mentioned likewise, that
carbon and the elements of water form the prin-
cipal constituents of vegetables ; the quantity of
the substances which do not possess this composi-
tion being in very small proportion. Now, the
relative quantity of oxygen in the whole mass
is less than in carbonic acid. It is therefore cer-
tain, that plants must possess the power of de-
composing carbonic acid, since they appropriate
its carbon for their own use. The formation of
their principal component substances must ne-
cessarily be attended with the separation of the
carbon of the carbonic acid from the oxygen,
which must be returned to the atmosphere, whilst
the carbon enters into combination with water or
its elements. The atmosphere must thus receive a
c2
20 OF THE ASSIMILATION OF CARBON.
volume of oxygen for every volume of carbonic acid
which has beeji decomposed.
This remarkable property of plants has been
demonstrated in the most certain manner, and it
is in the power of every person to convince himself
of its existence. The leaves and other green parts
of a plant absorb carbonic acid, and emit an equal
volume of oxygen. They possess this property
quite independently of the plant ; for if, after being
separated from the stem, they are placed in water
containing carbonic acid, and exposed in that con-
dition to the sun's light, the carbonic acid is, after
a time, found to have disappeared entirely from
the water. If the experiment is conducted under
a glass receiver filled with water, the oxygen
emitted from the plant may be collected and exa-
mined. When no more oxygen gas is evolved, it
is a sign that all the dissolved carbonic acid is
decomposed ; but the operation recommences if a
new portion of it is added.
Plants do not emit gas when placed in water
which either is free from carbonic acid, or contains
an alkali that protects it from assimilation.
These observations were first made by Priestley
and Sennebier. The excellent experiments of De
Samsure have further shown, that plants increase
in weight during the decomposition of carbonic
acid and separation of oxygen. This increase in
weight is greater than can be accounted for by the
quantity of carbon assimilated ; a fact which con-
ITS SOURCE, THE ATMOSPHERE. 21
firms the view, that the elements of water are assi-
milated at the same time.
The life of plants is closely connected with that
of animals, in a most simple manner, and for a wise
and sublime purpose.
The presence of a rich and luxuriant vegetation
may be conceived without the concurrence of
animal life, but the existence of animals is un-
doubtedly dependent upon the life and develop-
ment of plants.
Plants not only afford the means of nutrition for
the growth and continuance of animal organization,
but they likewise furnish that which is essential for
the support of the important vital process of respira-
tion ; for besides separating all noxious matters
from the atmosphere, they are an inexhaustible
source of pure oxygen, which supplies the loss
which the air is constantly sustaining. Animals
on the other hand expire carbon, which plants in-
spire ; and thus the composition of the medium
in which both exist, namely, the atmosphere, is
maintained constantly unchanged.
It may be asked, Is the quantity of carbonic
acid in the atmosphere, which scarcely amounts to
l-10th per cent., sufficient for the wants of the
whole vegetation on the surface of the earth, — is
it possible that the carbon of plants has its origin
from the air alone ? This question is very easily
answered. It is known, that a column of air of
2216.66 Ibs. weight, Hessian measure, rests upon
22 OF THE ASSIMILATION OF CARBON.
every square Hessian foot of the surface of the earth ;
the diameter of the earth and its superficies are like-
wise known, so that the weight of the atmosphere
can be calculated with the greatest exactness. The
thousandth part of this is carbonic acid, which
contains upwards of 27 per cent, carbon. By this
calculation it can be shown, that the atmosphere
contains 3000 billion Hessian Ibs. of carbon; a
quantity which amounts to more than the weight
of all the plants, and of all the- strata of mineral
and brown coal, which exist upon the earth. This
carbon is, therefore, more than adequate to all the
purposes for which it is required. The quantity
of carbon contained in sea- water, is proportionally
still greater.
If, for the sake of argument, we suppose the super-
ficies of the leaves and other green parts of plants,
by which the absorption of carbonic acid is effected,
to be double that of the soil upon which they grow,
a supposition which is much under the truth in the
case of woods, meadows, and corn fields ; and if we
further suppose that carbonic acid equal to 0.00067
of the volume of the air, or 1-1 000th of its weight
is abstracted from it during every second of time,
for eight hours daily, by a field of 80,000 Hessian
square feet; then those leaves would receive 1000
Hessian Ibs. of carbon in 200 days.*
* The quantity of carbonic acid which can be extracted from the air
in a given time, is shown by the following calculation. During the
whitewashing of a small chamber, the superficies of the walls and roof
ITS SOURCE, THE ATMOSPHERE. 23
But it is inconceivable, that the functions of the
organs of a plant can cease for any one moment
during its life. The roots and other parts of it,
which possess the same power, absorb constantly
water and carbonic acid. This power is indepen-
dent of solar light. During the day, when the
plants are in the shade, and during the night, car-
bonic acid is accumulated in all parts of their
structure ; and the assimilation of the carbon and
the exhalation of oxygen commence from the instant
that the rays of the sun strike them. As soon as a
young plant breaks through the surface of the
ground, it begins to acquire colour from the top
downwards ; and the true formation of woody tissue
commences at the same time.
The proper, constant, and inexhaustible sources
of oxygen gas are the tropics and warm climates,
where a sky, seldom clouded, permits the glowing
of which we will suppose to be 1 05 square metres, and which receives
six coats of lime in fou* days, carbonic acid is abstracted from the air,
and the lime is consequently converted, on the surface, into a carbonate.
It has been accurately determined that one square decimetre receives in
this way, a coating of carbonate of lime which weighs 0.732 grammes.
Upon the 105 square metres already mentioned there must accordingly
be formed 7686 grains of carbonate of lime, which contain 4325.6
grains of carbonic acid. The weight of one cubic decimetre of carbonic
acid being calculated at two grammes, (more accurately 1.97978,) the
above mentioned surface must absorb in four days 2.163 cubic metres of
carbonic acid. 2500 square metres (one Hessian acre) would absorb,
under a similar treatment, 514 cubic metres zz 3296 cubic feet of car-
bonic acid in four days. In 200 days it would absorb 2575 cubic metres
— 164,800 cubic feet, which contain 10,300 Ibs. Hessian of carbonic acid
of which 2997 Ibs. are carbon, a quantity three times as great as that
which is assimilated by the leaves and roots growing upon the same
space.
24 OF THE ASSIMILATION OF CARBON.
rays of the sun to shine upon an immeasurably
luxuriant vegetation. The temperate and cold
zones, where artificial warmth must replace deficient
heat of the sun, produce, on the contrary, carbonic
acid in superabundance, which is expended in the
nutrition of the tropical plants. The same stream
of air, which moves by the revolution of the earth
from the equator to the poles, brings to us, in its
passage from the equator, the oxygen generated
there, and carries away the carbonic acid formed
during our winter.
The experiments of De Saussure have proved, that
the upper strata of the air contain more carbonic
acid than the lower, which are in contact with
plants ; and that the quantity is greater by night
than by day, when it undergoes decomposition.
Plants thus improve the air, by the removal of
carbonic acid, and by the renewal of oxygen, which
is immediately applied to the use of man and
animals. The horizontal currents of the atmo-
sphere bring with them as much as they carry
away, and the interchange of air between the
upper and lower strata, which their difference of
temperature causes, is extremely trifling when
compared with the horizontal movements of the
winds. Vegetable culture heightens the healthy
state of a country, and a previously healthy country
would be rendered quite uninhabitable by the ces-
sation of all cultivation.
The most important function in the life of plants,
ITS SOURCE, THE ATMOSPHERE. 25
or, in other words, in their assimilation of carbon,
is the separation, we might almost say the genera-
tion, of oxygen. No matter can be considered as
nutritious, or as necessary to the growth of plants,
which possesses a composition either similar to or
identical with theirs, and the assimilation of which,
therefore, could take place without exercising this
function.
In the second part of this work, we shall adduce
satisfactory proofs that decayed woody fibre (humus)
contains carbon and the elements of water, without
an excess of oxygen ; its composition differing from
that of woody fibre, in its being richer in carbon.
Vegetable physiologists consider the formation
of woody fibre from humus as very simple ; they
say, humus has only to enter into chemical com-
bination with water, in order to effect the formation
of woody fibre, starch, or sugar *.
But the same philosophers have informed us,
that aqueous solutions of sugar, starch and gum, are
imbibed by the roots of plants, and carried to all
parts of their structure, but are not assimilated ; they
cannot therefore be employed in their nutrition.
We could scarcely conceive a form more convenient
for assimilation than that of gum, starch, and
sugar, for they all contain the elements of woody
fibre, and nearly in the same proportions.
All the erroneous opinions concerning the mo-
* Mcyen, Pflanzenphysiologie, ii. s. 141.
26 OF THE ASSIMILATION OF CARBON.
dus operandi of humus have their origin in the
false notions entertained respecting the most im-
portant vital functions of plants ; analogy, that
fertile source of error, having unfortunately led to
the very unapt comparison of the vital functions
of plants with those of animals.
Substances, such as sugar, starch, &c. which con-
tain carbon and the elements of water, are products
of the life of plants, which live only whilst they
generate them. The same may be said of humus, for
it can be formed in plants, like the former sub-
stances. Smitkson, Jameson, and Thomson, found,
that the black excretions of unhealthy elms, oaks,
and horse-chesnuts, consisted of humic acid in com-
bination with alkalies. Berzelius detected similar
products in the bark of most trees. Now, can it
be supposed, that the diseased organs of a plant
possess the power of generating the matter, to which
its sustenance and vigour are ascribed ?
How does it happen, it may be asked, that the
absorption of carbon from the atmosphere by
plants is doubted by all botanists and vegetable
physiologists, and that by the greater number the
purification of the air by means of them is wholly
denied ?
These doubts have arisen from the action of plants
on the air in the absence of light, that is, during the
night.
The experiments of Ingenhouss were in a great
measure the cause of this uncertainty of opinion,
INFLUENCE OF THE SHADE ON PLANTS. 27
regarding the influence of plants in purifying the
air. His observation., that green plants emit car-
bonic acid in the dark, led De Saussure and
Grischow to new investigations, by which they
ascertained that under such conditions plants do
really absorb oxygen, and emit carbonic acid ; but
that the whole volume of air undergoes diminution
at the same time. From the latter fact it follows,
that the quantity of oxygen gas absorbed is greater,
than the volume of carbonic acid separated ; for if
this were not the case, no diminution could occur.
These facts cannot be doubted, but the views based
on them have been so false, that nothing, except the
total want of observation, and the utmost ignorance
of the chemical relations of plants to the atmo-
sphere, can account for their adoption.
It is known, that nitrogen, hydrogen, and a num-
ber of other gases, exercise a peculiar, and, in ge-
neral, an injurious influence upon living plants. Is
it, then, probable, that oxygen, one of the most
energetic agents in nature, should remain without
influence on plants when one of their peculiar pro-
cesses of assimilation has ceased ?
It is true, that the decomposition of carbonic
acid is arrested by absence of light. But then,
namely, at night, a true chemical process com-
mences, in consequence of the action of the oxygen
in the air, upon the organic substances composing
the leaves, blossoms, and fruit. This process is not
at all connected with the life of the vegetable or-
28 OF THE ASSIMILATION OF CARBON.
ganism, because it goes on in a dead plant exactly
as in a living one.
The substances composing the leaves of different
plants being known, it is a matter of the greatest
ease and certainty, to calculate which of them, du-
ring life, should absorb most oxygen by chemical
action, when the influence of light is withdrawn.
The leaves and green parts of all plants, contain-
ing volatile oils or volatile constituents in general,
which change into resin by the absorption of oxy-
gen, should absorb more than other parts which
are free from such substances. Those leaves, also,
which contain either the constituents of nut-galls,
or compounds, in which nitrogen is present, ought
to absorb more oxygen than those which do not
contain such matters. The correctness of these
inferences has been distinctly proved by the obser-
vations of De Saussure ; for, whilst the tasteless
leaves of the Agave americana absorb only 0.3 of
their volume of oxygen, in the dark, during 24
hours, the leaves of the Pinus Abies, which contain
volatile and resinous oils, absorb 1 0 times, those of
the Quercus Robur containing tannic acid 1 4 times,
and the balmy leaves of the Populus alba 2 1 times
that quantity. This chemical action is shown, very
plainly, also in the leaves of the Cotyledon calycinwn,
the Cacalia ficoides and others ; for they are sour
like sorrel in the morning, tasteless at noon, and
bitter in the evening. The formation of acids is
effected during the night, by a true process of oxi-
INFLUENCE OF THE SHADE ON PLANTS. 29
dation : these are deprived of their acid properties
during the day and evening, and are changed, by
separation of a part of their oxygen, into compounds
containing oxygen and hydrogen, either in the
same proportions as in water, or even with an ex-
cess of hydrogen, which is the composition of all
tasteless and bitter substances.
Indeed, the quantity of oxygen absorbed could
be estimated pretty nearly, by the different periods,
which the green leaves of plants require to undergo
alteration in colour, by the influence of the atmo-
sphere. Those which continue longest green, will
abstract less oxygen from the air in an equal space
of time, than those, the constituent parts of which
suffer a more rapid change. It is found, for ex-
ample, that the leaves of the Ilex aquifolium, dis-
tinguished by the durability of their colour, absorb
only 0.86 of their volume of oxygen gas, in the
same time that the leaves of the poplar absorb 8,
and those of the beech 9^ times their volume ; both
the beech and poplar being remarkable for the
rapidity and ease with which the colour of their
leaves changes.
When the green leaves of the poplar, the beech,
the oak, or the holly, are dried under the air pump,
with exclusion of light, then moistened with water,
and placed under a glass globe filled with oxygen ;
they are found to absorb that gas in proportion as
they change in colour. The chemical nature of
this process is thus completely established. The
30 OF THE ASSIMILATION OF CARBON,
diminution of the gas which occurs, can only be
owing to the union of a large proportion of oxygen
with those substances which are already in the state
of oxides, or to the oxidation of the hydrogen, in
those vegetable compounds which contain it in ex-
cess. The fallen brown or yellow leaves of the oak
contain, no longer, tannin, and those of the poplar
no balsamic constituents.
The property which green leaves possess, of ab-
sorbing oxygen, belongs also to fresh wood, whether
taken from a twig, or from the interior of the trunk
of a tree. When fine chips of such wood are placed
in a moist condition, under a jar filled with oxygen,
the gas is seen to diminish in volume. But, wood,
dried by exposure to the atmosphere and then
moistened, converts the oxygen into carbonic acid,
without change of volume ; fresh wood, therefore,
absorbs most oxygen.
MM. Petersen and Schodler have shown, by the
careful elementary analyses of 24 different kinds of
wood, that they contain carbon and the elements of
water, with the addition of a certain quantity of
hydrogen. Oak wood, recently taken from the
tree, and dried at 100° C. (212° F.), contains 49.432
carbon, 6.069 hydrogen, and 44.499 oxygen.
The proportion of hydrogen, which is necessary
to combine with 44.498 oxygen in order to form
water, is ^ of this quantity, namely 5.56 ; it is evi-
dent, therefore, that oak wood contains ^ more
hydrogen than corresponds to this proportion.
INFLUENCE OF THE SHADE ON PLANTS. 31
In Pinus Larix, P. Abies, and P. picea, the excess
of hydrogen amounts to y, and in Tilia europcea
to |. The quantity of hydrogen stands in some
relation to the specific weight of the wood ; the
lighter kinds of wood contain more of it than the
heavier. In ebony wood (Diospyros Ebenum) the
oxygen and hydrogen are in exactly the same pro-
portion as in water.
The difference between the composition of the
varieties of wood, and that of simple woody fibre,
depends, unquestionably, upon the presence of con-
stituents, in part soluble, and in part insoluble, such
as resin and other matters, which contain a large
proportion of hydrogen : the hydrogen of such sub-
stances being in the analysis of the various woods
superadded to that of the true woody fibre.
It has previously been mentioned, that moulder-
ing oak wood contains carbon and the elements of
water without any excess of hydrogen. But the
proportions of its constituents must, necessarily,
have been different, if the volume of the air had
not changed during its decay, because the propor-
tion of hydrogen in those component substances
of the wood which contained it in excess is here
diminished, and this diminution could only be
effected by an absorption of oxygen.
Most vegetable physiologists have connected the
emission of carbonic acid during the night, with
the absorption of oxygen from the atmosphere, and
have considered these actions as a true process of
32 OF THE ASSIMILATION OF CARBON.
respiration in plants, similar to that of animals, and
like it, having for its result the separation of car-
bon from some of their constituents. This opinion
has a very weak and unstable foundation.
The carbonic acid, which has been absorbed by
the leaves and by the roots, together with water,
ceases to be decomposed on the departure of day-
light ; it is dissolved in the juices, which pervade
all parts of the plant, and escapes every moment
through the leaves, in quantity corresponding to
that of the water, which evaporates.
A soil, in which plants vegetate vigorously, con-
tains a certain quantity of moisture, which is indis-
pensably necessary to their existence. Carbonic
acid, likewise, is always present in such a soil, whe-
ther it has been abstracted from the air, or has been
generated by the decay of vegetable matter. Rain
and well water, as well as that from other sources,
invariably contain carbonic acid. Plants during
their life constantly possess the power of absorbing
by their roots moisture, and, along with it, air and
carbonic acid. Is it, therefore, surprising, that the
carbonic acid should be returned, unchanged, to
the atmosphere, along with water, when light (the
cause of the fixation of its carbon) is absent ?
Neither this emission of carbonic acid nor the
absorption of oxygen has any connexion with the
process of assimilation ; nor have they the slightest
relation to one another ; the one is a purely me-
chanical, the other a purely chemical process. A
EXHALATION OF OXYGEN BY PLANTS. 33
cotton wick, inclosed in a lamp, which contains a
liquid saturated with carbonic acid, acts exactly in
the same manner as a living plant in the night.
Water and carbonic acid are sucked up by capillary
attraction, and both evaporate from the exterior
part of the wick.
Plants, which live in a soil containing humus,
exhale much more carbonic acid during the night
than those which grow in dry situations ; they also
yield more in rainy than in dry weather. These
facts point out to us the cause of the numerous
contradictory observations, which have been made
with respect to the change impressed upon the air
by living plants, both in darkness, and in common
day-light, but which are unworthy of consideration,
as they do not assist in the solution of the main
question.
There are other facts which prove in a decisive
manner that plants yield more oxygen to the at-
mosphere than they extract from it ; these proofs,
however, are to be drawn with certainty only from
plants which live under water.
When pools and ditches, the bottoms of which
are covered with growing plants, freeze upon their
surface in winter, so that the water is completely
excluded from the atmosphere, by a clear stratum
of ice, small bubbles of gas are observed to escape,
continually, during the day, from the points of the
leaves and twigs. These bubbles are seen most
distinctly when the rays of the sun fall upon the ice ;
D
34 OF THE ASSIMILATION OF CARBON.
they are very small at first, but collect under the
ice and form larger bubbles. They consist of pure
oxygen gas. Neither during the night, nor during
the day when the sun does not shine, are they ob-
served to diminish in quantity. The source of this
oxygen is the carbonic acid dissolved in the water,
which is absorbed by the plants, but is again sup-
plied to the water, by the decay of vegetable sub-
stances contained in the soil. If these plants absorb
oxygen during the night, it can be in no greater
quantity than that which the surrounding water
holds in solution, for the gas, which has been ex-
haled, is not again absorbed. The action of water-
plants cannot be supposed to form .an exception
to a great law of nature, and the less so, as the
different action of aerial plants upon the atmosphere
is very easily explained.
The opinion is not new that the carbonic acid of
the air serves for the nutriment of plants, and that
its carbon is assimilated by them ; it has been
admitted, defended, and argued for, by the soundest
and most intelligent natural philosophers, namely,
by Priestley, Sennebier, De Saussure, and even by
Ingenhouss himself. There scarcely exists a theory
in natural science, in favour of which there are
more clear and decisive arguments. How, then, are
we to account for its not being received in its full
extent by most other physiologists, for its being
even disputed by many, and considered by a few as
quite refuted ?
NEGLECT OF CHEMISTRY BY BOTANISTS. 35
All this is due to two causes, which we shall now
consider.
One is, that in botany the talent and labour of
inquirers has been wholly spent in the examination
of form and structure : chemistry and physics have
not been allowed to sit in council upon the expla-
nation of the most simple processes ; their expe-
rience and their laws have not been employed,
though the most powerful means of help in the
acquirement of true knowledge. They have not
been used, because their study has been neglected.
All discoveries in physics and in chemistry, all
explanations of chemists, must remain without
fruit and useless, because, even to the great leaders
in physiology, carbonic acid, ammonia, acids, and
bases, are sounds without meaning, words without
sense, terms of an unknown language, which
awaken no thoughts and no associations. They
treat these sciences like the vulgar, who despise
a foreign literature in exact proportion to their
ignorance of it ; since even when they have had
some acquaintance with them, they have not under-
stood their spirit and application.
Physiologists reject the aid of chemistry in their
inquiry into the secrets of vitality, although it alone
could guide them in the true path ; they reject
chemistry, because in its pursuit of knowledge it
destroys the subjects of its investigation ; but they
forget that the knife of the anatomist must dis-
member the body, and destroy its organs, if an
D 2
36 OF THE ASSIMILATION OF CARBON.
account is to be given of their form, structure, and
functions.
When pure potato starch is dissolved in nitric
acid, a ring of the finest wax remains. What can be
opposed to the conclusion of the chemist, that each
grain of starch consists of concentric layers of wax
and amylum, which thus mutually protect each other
against the action of water and ether ? Can results
of this kind, which illustrate so completely both the
nature and properties of bodies; be attained by the
microscope ? 'Is it possible to make the gluten in
a piece of bread visible in all its connexions and
ramifications ? It is impossible by means of instru-
ments ; but if the piece of bread is placed in a
lukewarm decoction of malt, the starch, and the
substance called dextrine, are seen to dissolve
like sugar in water, and, at last, nothing remains
except the gluten, in the form of a spongy mass,
the minute pores of which can be seen only by a
microscope.
Chemistry offers innumerable resources of this
kind which are of the greatest use in an inquiry
into the nature of the organs of plants, but they are
not used, because the need of them is not felt. The
most important organs of animals and their func-
tions are known, although they may not be visible
to the naked eye. But, in vegetable physiology,
a leaf is in every case regarded merely as a leaf,
notwithstanding that leaves generating oil of tur-
pentine or oil of lemons must possess a different
OBJECT OF EXPERIMENTS IN PHYSIOLOGY. 37
nature from those in which oxalic acid is formed.
Vitality, in its peculiar operations, makes use of a
special apparatus for each function of an organ. A
rose twig engrafted upon a lemon-tree, does not
bring forth lemons but roses. Vegetable physiolo-
gists in the study of their science have not directed
their attention to that part of it which is most
worthy of investigation.
The second cause of the incredulity with which
physiologists view the theory of the nutrition of
plants by the carbonic acid of the atmosphere is,
that the art of experimenting is not known in phy-
siology, it being an art which can be learned accu-
rately only in the chemical laboratory. Nature
speaks to us in a peculiar language, in the language
of phenomena ; she answers at all times the ques-
tions which are put to her ; and such questions are
experiments. An experiment is the expression of
a thought : we are near the truth when the pheno-
menon, elicited by the experiment, corresponds to
the thought ; while the opposite result shows that
the question was falsely stated, and that the con-
ception was erroneous.
The critical repetition of another's experiments
must be viewed as a criticism of his opinions ; if
the result of the criticism be merely negative, if it
dcSfnot suggest more correct ideas in the place of
those which it is intended to refute, it should be
disregarded ; because the worse experimenter the
critic is, the greater will be the discrepancy between
38 OF THE ASSIMILATION OF CARBON.
the results he obtains and the views proposed by
the other.
It is too much forgotten by physiologists, that
their duty really is not to refute the experiments of
others, nor to show that they are erroneous, but to
discover truth, and that alone. It is startling, when
we reflect that all the time and energy of a multi-
tude of persons of genius, talent, and knowledge,
are expended in endeavours to demonstrate each
other's errors.
The question whether carbonic acid is the food
of plants or not, has been made the subject of
experiments with perfect zeal and good faith ; the
results have been opposed to that view. But how
was the inquiry instituted ?
The seeds of balsamines, beans, cresses, and
gourds, were sown in pure Carrara marble, and
sprinkled with water containing carbonic acid.
The seeds sprang, but the plants did not attain
to the development of the third small leaf. In
other cases, they allowed the water to penetrate
the marble from below, yet, in spite of this, they
died. It is worthy of observation, that they lived
longer with pure distilled water than with that
impregnated with carbonic acid ; but- still, in this
case also, they eventually perished. Other experi-
menters sowed seeds of plants in flowers of sulphur
and sulphate of baryta, and tried to nourish them
with carbonic acid, but without success.
Such experiments have been considered as posi-
CONDITIONS ESSENTIAL TO NUTRITION. 39
tive proofs, that carbonic acid will not nourish
plants ; but the manner in which they were insti-
tuted is opposed to all rules of philosophical inquiry,
and to all the laws of chemistry.
Many conditions are necessary for the life of
plants ; those of each genus require special condi-
tions, and should but one of these be wanting,
although all the rest be supplied, the plants will
not be brought to maturity. The organs of a
plant, as well as those of an animal, contain sub-
stances of the most different kinds ; some are formed
solely of carbon and the elements of water, others
contain nitrogen, and in all plants we find metallic
oxides in the state of salts. The food which can
serve for the production of all the organs of a plant,
must necessarily contain all its elements. These
most essential of all the chemical qualities of nutri-
ment may be united in one substance, or they may
exist separately in several ; in which case, the one
contains what is wanting in the other. Dogs die
although fed with jelly, a substance which contains
nitrogen ; they cannot live upon white bread, sugar,
or starch, if these are given as food, to the exclu-
sion of all other substances. Can it be concluded
from this, that these substances contain no elements
suited for assimilation ? Certainly not.
Vitality is the power which each organ possesses
of constantly reproducing itself ; for this it requires
a supply of substances which contain the consti-
tuent elements of its own substance, and are capable
40 OF THE ASSIMILATION OF CARBON.
of undergoing transformation. All the organs to-
gether cannot generate a single element, carbon,
nitrogen, or a metallic oxide.
When the quantity of the food is too great, or is
not capable of undergoing the necessary transfor-
mation, or exerts any peculiar chemical action, the
organ itself is subjected to a change : all poisons
act in this manner. The most nutritious sub-
stances may cause death. In experiments such as
those described above, every condition of nutrition
should be considered. Besides those matters which
form their principal constituent parts, both animals
and plants require others, the peculiar functions
of which are unknown. These are inorganic sub-
stances, such as common salt, the total want of which
is in animals inevitably productive of death. Plants,
for the same reason, cannot live unless supplied
with certain metallic compounds.
If we knew with certainty that there existed a sub-
stance capable, alone, of nourishing a plant and of
bringing it to maturity, we might be led to a know-
ledge of the conditions necessary to the life of all
plants, by studying its characters and composition.
If humus were such a substance, it would have
precisely the same value as the only single food
which nature has produced for animal organisation,
namely, milk (Prout). The constituents of milk,
are cheese or caseine, a compound containing nitro-
gen in large proportion ; butter, in which hydrogen
abounds, and sugar of milk, a substance with a
CONDITIONS ESSENTIAL TO NUTRITION. 41
large quantity of hydrogen and oxygen in the
same proportion^ as in water. It also contains
in solution, lactate of soda, phosphate of lime, and
common salt ; and a peculiar aromatic product
exists in the butter, called butyric acid. The
knowledge of the composition of milk is a key to
the conditions necessary for the purposes of nutri-
tion of all animals.
All substances which are adequate to the nourish-
ment of animals, contain those materials united,
though not always in the same form ; nor can
any one be wanting, for a certain space of time,
without a marked effect on the health being pro-
duced. The employment of a substance as food,
presupposes a knowledge of its capacity of assimi-
lation, and of the conditions under which this takes
place.
A carnivorous animal dies in the vacuum of an
air-pump, even though supplied with a supera-
bundance of food ; it dies in the air, if the demands
of its stomach are not satisfied ; and it dies in pure
oxygen gas, however lavishly nourishment be given
to it. Is it hence to be concluded, that neither
flesh, nor air, nor oxygen, is fitted to support life ?
Certainly not.
From the pedestal of the Trajan column at
Rome, we might chisel out each single piece of
stone, if, upon the extraction of the second, we re-
placed the first. But could we conclude from this,
that the column was suspended in the air, and not
42 OF THE ASSIMILATION OF CARBON.
supported by a single piece of its foundation ?
Assuredly not. Yet the strongest proof would have
been given, that each portion of the pedestal could
be removed without the downfall of the column.
Animal and vegetable physiologists, however,
come to such conclusions with respect to the pro-
cess of assimilation. They institute experiments
without being acquainted with the circumstances
necessary for the continuance of life — with the
qualities and proper nutriment of the animal or
plant on which they operate — or with the nature
and chemical constitution of its organs. These
experiments are considered by them as convinc-
ing proofs, whilst they are fitted only to awaken
pity.
Is it possible to bring a plant to maturity by
means of carbonic acid and water, without the aid
of some substance containing nitrogen, which is an
essential constituent of the sap, and indispensable
for its production ? Must the plant not die, how-
ever abundant the supply of carbonic acid may be,
as soon as the first small leaves have exhausted
the nitrogen contained in the seeds ?
Can a plant be expected to grow in Carrara
marble, even when an azotized substance is supplied
to it, but when the marble is sprinkled with an
aqueous solution of carbonic acid, which dissolves
the lime and forms super carbonate of lime ? A
plant of the family of the Plumbaginece, upon the
leaves of which fine hornlike, or scaly processes of
CONDITIONS ESSENTIAL TO NUTRITION. 43
crystallised carbonate of lime are formed, might,
perhaps, attain maturity under such circumstances ;
but these experiments alone are sufficient to prove,
that cresses, gourds, and balsamines, cannot be
nourished by supercarbonate of lime, in the absence
of matter containing nitrogen. We may indeed
conclude, that the salt ofc lime acts as a poison,
since the development of plants will advance fur-
ther in pure water, when lime and carbonic acid
are not used.
Moist flowers of sulphur attract oxygen from the
atmosphere and become acid. Is it possible that a
plant can grow and flourish in presence of free
sulphuric acid, with no other nourishment than
carbonic acid ? It is true, the quantity of sulphuric
acid formed thus in hours, or in days, may be small,
but the property of each particle of the sulphur
to absorb oxygen and retain it, is present every
moment.
When it is known that plants require moisture,
carbonic acid, and air, should we choose, as the
soil for experiments on their growth, sulphate of
barytes, which, from its nature and specific gravity,
completely prevents the access of air ?
All these experiments are valueless for the decision
of any question. It is absurd to take for them any
soil at mere hazard, as long as we are ignorant of
the functions performed in plants by those inor-
ganic substances which are apparently foreign to
them. It is quite impossible to mature a plant of
44 ORIGIN AND ACTION OF HUMUS.
the family of the Graminetz, or of the Equisetacece,
the solid framework of which contains silicate of
potash, without silicic acid and potash, or a plant of
the genus Oxalis without potash, or saline plants
such as the saltworts (Salsola and Salicornia),
without chloride of sodium, or at least some salt of
similar properties. All seeds of the Grammes con-
tain phosphate of magnesia ; the solid parts of the
roots of the altlicea contain more phosphate of lime
than woody fibre. Are these -substances merely
accidentally present ? A plant should not be
chosen for experiment, when the matter which it
requires for its assimilation is not well known.
What value, now, can be attached to experiments
in which all those matters which a plant requires
in the process of assimilation, besides its mere nutri-
ment, have been excluded with the greatest care ?
Can the laws of life be investigated in an organized
being which is diseased or dying ?
The mere observation of a wood or meadow is
infinitely better adapted to decide so simple a ques-
tion, than all the trivial experiments under a glass
globe ; the only difference is, that instead of one
plant there are thousands. When we are acquainted
with the nature of a single cubic inch of their soil,
and know the composition of the air and rain-
water, we are in possession of all the conditions
necessary to their life. The source of the different
elements entering into the composition of plants
cannot possibly escape us, if we know in what form
DECAY OF WOODY FIBRE. 45
they take up their nourishment, and compare its
composition with that of the vegetable substances
which compose their structure.
* All these questions will now be examined and
discussed. It has been already shown, that the
carbon of plants is derived from the atmosphere :
it still remains for us to inquire, what power is ex-
erted on vegetation by the humus of the soil and
the inorganic constituents of plants, and also to
trace the sources of their nitrogen.
ON THE ORIGIN AND ACTION OF HUMUS.
It will be shown in the second part of this work,
that all plants and vegetable structures undergo
two processes of decomposition after death. One
of these is named fermentation, the other decay,
putrefaction, or eremacausis* :.
It will likewise be shown, that decay is a slow
process of combustion, a process, therefore, in
which the combustible parts of a plant unite with
the oxygen of the atmosphere.
The decay of woody fibre (the principal consti-
tuent of all plants) is accompanied by a pheno-
menon of a peculiar kind. This substance, in
contact with air or oxygen gas, converts the latter
into an equal volume of carbonic acid, and its decay
* The word eremacausis was proposed by the author some time since,
in order to explain the true nature of putrefaction ; it is compounded
from -/jpe'jua alow and Kav<ns combustion.
46 ORIGIN AND ACTION OF HUMUS.
ceases upon the disappearance of the oxygen. If
the carbonic acid is removed, and oxygen replaced,
its decay recommences, that is, it again converts
oxygen into carbonic acid. Woody fibre consists of
carbon and the elements of water ; and if we judge
only from the products formed during its decom-
position, and from those formed by pure charcoal,
burned at a high temperature, we might conclude
that the causes were the same in both : the decay
of woody fibre proceeds, therefore, as if no hydro-
gen or oxygen entered into its composition.
A very long time is required for the completion
of this process of combustion, and the presence of
water is necessary for its maintenance : alkalies
promote it, but acids retard it ; all antiseptic sub-
stances, such as sulphurous acid, the mercurial
salts, empyreumatic oils, &c. cause its complete
cessation*
Woody fibre, in a state of decay, is the substance
called humus*.
The property of woody fibre to convert surround-
ing oxygen gas into carbonic acid diminishes in
proportion as its decay advances, and at last a
certain quantity of a brown coaly-looking substance
remains, in which this property is entirely wanting.
This substance is called mould ; it is the product of
the complete decay of woody fibre. Mould consti-
* The humic acid of chemists is a product of the decomposition of
humus by alkalies; it does not exist in the humus of vegetable physio-
logists.
IT EVOLVES CARBONIC ACID. 47
tutes the principal part of all the strata of brown
coal and peat.
Humus acts in the same manner in a soil per-
meable to air as in the air itself; it is a continued
source of carbonic acid, which it emits very slowly.
An atmosphere of carbonic acid, formed at the
expense of the oxygen of the air, surrounds every
particle of decaying humus. The cultivation of
land, by tilling and loosening the soil, causes
a free and unobstructed access of air. An atmo-
sphere of carbonic acid is, therefore, contained
in every fertile soil, and is the first and most
important food for the young plants which grow
in it.
In spring, when those organs of plants are absent,
which nature has appointed for the assumption of
nourishment from the atmosphere, the component
substance of the seeds is exclusively employed in
the formation of the roots. Each new radicle fibril
which a plant acquires may be regarded as consti-
tuting at the same time a mouth, a lung, and a
stomach. The roots perform the functions of the
leaves from the first moment of their formation ;
they extract from the soil their proper nutri-
ment, namely, the carbonic acid generated by the
humus.
By loosening the soil which surrounds young plants,
we favour the access of air, and the formation of
carbonic acid ; and on the other hand the quantity
of their food is diminished by every difficulty which
48 ORIGIN AND ACTION OF HUMUS.
opposes the renewal of air. A plant itself effects
this change of air at a certain period of its growth.
The carbonic acid, which protects the undecayed
humus from further change, is absorbed and taken
away by the fine fibres of the roots, and by the
roots themselves ; this is replaced by atmospheric
air, by which process the decay is renewed, and a
fresh portion of carbonic acid formed. A plant at
this time receives its food, both by the roots, and
by the organs above ground, and advances rapidly
to maturity.
When a plant is quite matured, and when the
organs, by which it obtains food from the atmo-
sphere, are formed, the carbonic acid of the soil is
no further required.
Deficiency of moisture in the soil, or its com-
plete dryness, does not now check the growth
of a plant, provided it receives from the dew
and the atmosphere as much as is requisite for
the process of assimilation. During the heat of
summer it derives its carbon exclusively from the
atmosphere.
We do not know what height and strength
nature has allotted to plants ; we are acquainted
only with the size which they usually attain.
Oaks are shown, both in London and Amsterdam,
as remarkable curiosities, which have been reared
by Chinese gardeners, and are only one foot and a
half in height, although their trunks, barks, leaves,
branches, and whole habitus, evince a venerable age.
GROWTH OF PLANTS. 49
The small turnip, grown at Tel tow,* when placed
in a soil which yields as much nourishment as it
can take up, increases to several pounds in weight.
The size of a plant is proportional to the surface
of the organs which are destined to convey food to
it. A plant gains another mouth and stomach
with every new fibre of root, and every new leaf.
The power which roots possess of taking up
nourishment does not cease as long as nutriment
is present. When the food of a plant is in greater
quantity than its organs require for their own per-
fect development, the superfluous nutriment is not
returned to the soil, but is employed in the forma-
tion of new organs. At the side of a cell, already
formed, another cell arises ; at the side of a twig
and leaf, a new twig and a new leaf are developed.
These new parts could not have been formed had
there not been an excess of nourishment. The
sugar and mucilage produced in the seeds, form
the nutriment of the young plants, and disappear
during the development of the buds, green sprouts,
and leaves.
The power of absorbing nutriment from the
atmosphere, with which the leaves of plants are
endowed, being proportionate to the extent of their
surface, every increase in the size and number of
these parts is necessarily attended with an increase
* Teltow is a village near Berlin, where small turnips are cultivated
in a sandy soil ; they are much esteemed, and weigh rarely above one
ounce.
E
50 ORIGIN AND ACTION OF HUMUS.
of nutritive power, and a consequent further deve-
lopment of new leaves and branches. Leaves, twigs,
and branches, when completely matured, as they
do not become larger, do not need food for their
support. For their existence as organs, they require
only the means necessary for the performance of
the special functions to which they are destined
by nature ; they do not exist on their own account.
We know that the functions of the leaves and
other green parts of plants are ' to absorb carbonic
acid, and with the aid of light and moisture, to
appropriate its carbon. These processes are con-
tinually in operation ; they commence with the
first formation of the leaves, and do not cease with
their perfect development. But the new products
arising from this continued assimilation, are no
longer employed by the perfect leaves ^in their own
increase : they serve for the formation of woody fibre,
and all the solid matters of similar composition.
The leaves now produce sugar, amylin or starch, and
acids, which were previously formed by the roots
when they were necessary for the development of
the stem, buds, leaves and branches of the plant.
The organs of assimilation, at this period of their
life, receive more nourishment from the atmo-
sphere than they employ in their own sustenance,
and when the formation of the woody substance
has advanced to a certain extent, the expenditure
of the nutriment, the supply of which still remains
the same, takes a new direction, and blossoms are
TRANSFORMATIONS OF ORGANIC SUBSTANCES. 51
produced. The functions of the leaves of most
plants cease upon the ripening of their fruit, because
the products of their action are no longer needed.
They now yield to the chemical influence of the
oxygen of the ah*, generally suffer therefrom a
change in colour, and fall off.
A peculiar " transformation" of the matters con-
tained in all plants takes place in the period be-
tween blossoming and the ripening of the fruit ;
new compounds are produced, which furnish con-
stituents of the blossoms, fruit, and seed. An
organic chemical "transformation" is the separation
of the elements of one or several combinations,
and their reunion into two or several others,
which contain the same number of elements, either
grouped in another manner, or in different propor-
tions. Of two compounds formed in consequence
of such a change, one remains as a component part
of the blossom or fruit, while the other is separated
by the roots in the form of excrementitious matter.
No process of nutrition can be conceived to subsist
in animals or vegetables, without a separation of
effete matters. We know, indeed, that an organised
body cannot generate substances,- but can only
change the mode of their combination, and that
its sustenance and reproduction depend upon the
chemical transformation of the matters which are
employed as its nutriment, and which contain its
own constituent elements.
Whatever we regard as the cause of these trans-
E 2
52 ORIGIN AND ACTION OF HUMUS.
formations, whether the Vital Principle, Increase
of Temperature, Light, Galvanism, or any other in-
fluence, the act of transformation is a purely che-
mical process. Combination and Decomposition can
take place only when the elements are disposed to
these changes. That which chemists name affinity
indicates only the degree in which they possess this
disposition. It will be shown, when considering
the processes of fermentation and putrefaction, that
every disturbance of the mutual attraction subsist-
ing between the elements of a body gives rise to a-
transformation. The elements arrange themselves
according to the degrees of their reciprocal attrac-
tion into new combinations, which are incapable of
further change, under the same conditions.
The products of these transformations vary with
their causes, that is, with the diiferent conditions
on which their production depended; and are
as innumerable as these conditions themselves.
The chemical character of an acid, for example,
is its unceasing disposition to saturation by means
of a base ; this disposition differs in intensity in
different acids ; but when it is satisfied, the acid
character entirely disappears. The chemical cha-
racter of a base is exactly the reverse of this, but
both an acid and a base, notwithstanding the great
difference in their properties, effect, in most cases,
the same kind of transformations.
Hydrocyanic acid and water contain the elements
of carbonic acid, ammonia, urea, cyanuric acid,
NATURE OF ORGANIC CHEMICAL PROCESSES. 53
cyanilic acid, oxalic acid, formic acid, melam, am-
melin, melamin, azulmin, melton, hydromellonic
acid, allantoin, fyc. It is well known, that all these
very different substances can be obtained from hy-
drocyanic acid and the elements of water, by vari-
ous chemical transformations.
The whole process of nutrition may be understood
by the consideration of one of these transformations.
Hydrocyanic acid and water, for example, when
brought into contact with muriatic acid, are decom-
posed into formic acid and ammonia ; both of these
products of decomposition contain the elements of
hydrocyanic acid and water, although in another
form, and arranged in a different order. The change
results from the strong disposition or struggle of
muriatic acid to undergo saturation, in consequence
of which the hydrocyanic acid and water suffer
mutual decomposition. The nitrogen of the hydro-
cyanic acid and the hydrogen of the water unite
together and form a base, ammonia, with which
the acid unites ; the chemical characters of the
acid being at the same time lost, because its desire
for saturation is satisfied by its uniting with am-
monia. Ammonia itself was not previously present,
but only its elements, and the power to form
it. The simultaneous decomposition of hydro-
cyanic acid and water in this instance does not
take place in consequence of the chemical affinity
of muriatic acid for ammonia, since hydrocyanic
acid and water contain no ammonia. An affinity
S4 ORIGIN AND ACTION OF HUMUS.
of one body for a second, which does not exist,
is quite inconceivable. The ammonia, in this
case, is formed only on account of the existing
attractive desire of the acid for saturation. Hence
we may perceive how much these modes of decom-
position, to which the name of transformations or
metamorphoses has been especially applied, differ
from the ordinary chemical decompositions.
In consequence of the formation of ammonia,
the other elements of hydrocyanic acid, namely,
carbon and hydrogen, unite with the oxygen of
the decomposed water, and form formic acid, the
elements of this substance with the power of com-
bination being present. Formic acid, here, repre-
sents the excrementitious matters ; ammonia, the
new substance, assimilated by an organ of a plant
or animal.
Each organ extracts from the food presented to it,
what it requires for its own sustenance ; while the
remaining elements, which are not assimilated,
combine together and are separated as excrement.
The excrementitious matters of one organ come in
contact with another during their passage through
the organism, and in consequence suffer new trans-
formations ; the useless matters rejected by one
organ containing the elements for the nutrition of
a second and a third organ ; but at last, being ca-
pable of no further transformations, they are sepa-
rated from the system by the organs destined for
that purpose. Each part of an organized being is
ORGANIC CHEMICAL PROCESSES. 55
fitted for its peculiar functions. A cubic inch of
sulphuretted hydrogen introduced into the lungs,
would cause instant death, but it is formed, under
a variety of circumstances, in the intestinal canal
without any injurious effect.
In consequence of such transformations as we
have described, excrements are formed of various
composition; some of these contain carbon, in
excess; others nitrogen, and others again hydrogen
and oxygen. The kidneys, liver, and lungs, are
organs of excretion; the first separate from the
body all those substances in which a large propor-
tion of nitrogen is contained; the second, those
with an excess of carbon ; and the third, such as
are composed principally of oxygen and hydrogen.
Alcohol, also, and the volatile oils which are inca-
pable of being assimilated, are exhaled through the
lungs, and not through the skin.
Respiration must be regarded as a slow process
of combustion or constant decomposition. If it be
subject to the laws which regulate the processes of
decomposition generally, the oxygen of the inspired
air cannot combine directly with the carbon of com-
pounds of that element contained in the blood; the
hydrogen only can combine with the oxygen of the
air, or undergo a higher degree of oxidation. Oxy-
gen is absorbed without uniting with carbon ; and
carbonic acid is disengaged, the carbon and oxygen
of which must be derived from matters previously
existing in the blood.
50 ORIGIN AND ACTION OF HUMUS.
All superabundant nitrogen is eliminated from
the body, as a liquid excrement, through the uri-
nary passages; all solid substances, incapable of
further transformation, pass out by the intestinal
canal, and all gaseous matters by the lungs.
We should not permit ourselves to be withheld,
by the idea of a vital principle, from considering,
in a chemical point of view, the process of the trans-
formation of the food, and its assimilation by the
various organs. This is the more necessary, as the
views, hitherto held, have produced no results, and
are quite incapable of useful application.
Is it truly vitality, which generates sugar in the
germ for the nutrition of young plants, or which
gives to the stomach the power to dissolve, and to
prepare for assimilation all the matter introduced
into it? A decoction of malt possesses as little
power to reproduce itself, as the stomach of a dead
calf; both are, unquestionably, destitute of life.
But when amylin or starch is introduced into a
decoction of malt, it changes, first into a gummy-
like matter, and lastly into sugar. Hard-boiled
albumen and muscular fibre can be dissolved in a
decoction of a calf's stomach, to which a few drops
of muriatic acid have been added, precisely as in
the stomach itself. * (Schwann, Schulz.)
The power, therefore, to effect transformations,
* This remarkable action has been completely confirmed in this
laboratory (Giessen), by Dr. Vogel, a highly distinguished young phy-
siologist.
ORGANIC CHEMICAL PROCESSES. 57
does not belong to the vital principle ; each trans-
formation is owing to a disturbance in the attrac-
tion of the elements of a compound, and is con-
sequently a purely chemical process. There is no
doubt, that this process takes place in another
form, from that of the ordinary decomposition of
salts, oxides, or sulphurets. But is it the fault of
chemistry that physiology has hitherto taken no
notice of this new form of chemical action?
Physicians are accustomed to administer whole
ounces of borax to patients suffering under urinary
calculi, when it is known, that the bases of all
alkaline salts, formed by organic acids, are carried
through the urinary passages in the form of alkaline
carbonates capable of dissolving calculi (Wohler).
Is this rational ? The medical reports state, that
upon the Rhine, where so much cream of tartar is
consumed in wine, the only cases of calculous dis-
orders are those which are imported from other
districts. We know that the uric acid calculus is
transformed into the mulberry calculus, (which con-
tains oxalic acid,) when patients suffering under the
former exchange the town, for the country, where
less animal and more vegetable food is used. Are
all these circumstances incapable of explanation ?
The volatile oil of the roots of valerian may be
obtained from the oil generated during the fer-
mentation of potatoes (Dumas), and the oil of the
Spircea ulmaria from the crystalline matter of the
bark of the willow. (Piria.) We are able to form
58 ORIGIN AND ACTION OF HUMUS.
in our laboratories, formic acid, oxalic acid, urea,
and the crystalline substances existing in the liquid
of the allantois of the cow, all products, it is said,
of the vital principle. We see, therefore, that this
mysterious principle has many relations in common
with chemical forces, and that the latter can indeed
replace it. What these relations are, it remains
for physiologists to investigate. Truly it would be
extraordinary, if this vital principle, which uses
everything for its own purposes, had allotted no
share to chemical forces, which stand so freely at
its disposal. We shall obtain that which is attain-
able in a rational inquiry into nature, if we sepa-
rate the actions belonging to chemical powers, from
those which are subordinate to other influences.
But the expression " vital principle " must, in the
meantime, be considered as of equal value with the
terms specific or dynamic in medicine : everything
is specific which we cannot explain, and dynamic is
the explanation of all which we do not understand.
Transformations of existing compounds are
constantly taking place during the whole life of a
plant, in consequence of which, and as the results
of these transformations, there are produced gaseous
matters which are excreted by the leaves and blos-
soms, solid excrements deposited in the bark, and
fluid soluble substances which are eliminated by the
roots. Such secretions are most abundant imme-
diately before the formation and during the continu-
ance of the blossoms; they diminish after the deve-
ITS USE EXPLAINED. 59
lopment of the fruit. Substances, containing a large
proportion of carbon, are excreted by the roots and
absorbed by the soil. Through the expulsion of
these matters unfitted for nutrition, therefore, the
soil receives again the greatest part of the carbon,
which it had at first yielded to the young plants as
food, in the form of carbonic acid.
The soluble matter, thus acquired by the soil, is
still capable of decay and putrefaction, and by un-
dergoing these processes furnishes renewed sources
of nutrition to another generation of plants ; it be-
comes humus. The leaves of trees, which fall in
the forest in autumn, and the old roots of grass in
the meadow, are likewise converted into humus by
the same influence : a soil receives more carbon
in this form than its decaying humus had lost as
carbonic acid.
Plants do not exhaust the carbon of a soil, in the
normal condition of their growth; on the contrary,
they add to its quantity. But if it is true that
plants give back more carbon to a soil than they
take from it, it is evident that their growth must
depend upon the reception of nourishment from
the atmosphere. The influence of humus upon
vegetation is explained by the foregoing facts, in
the most clear and satisfactory manner.
Humus does not nourish plants, by being taken
up and assimilated in its unaltered state, but by
presenting a slow and lasting source of carbonic
acid which is absorbed by the roots, and is the
60 ORIGIN AND ACTION OF HUMUS.
principal nutriment of young plants at a time when,
being destitute of leaves, they are unable to extract
food from the atmosphere.
In former periods of the earth's history, its sur-
face was covered with plants, the remains of which
are still found in the coal formations. These plants
— the gigantic monocotyledons, ferns, palms, and
reeds, belong to a class, to which nature has given the
power, by means of an immense extension of their
leaves, to dispense with nourishment from the soil.
They resemble, in this respect, the plants which we
raise from bulbs and tubers, and which live while
young upon the substances contained in their seed,
and require no food from the soil, when their exte-
rior organs of nutrition are formed. This class of
plants is, even at present, ranked amongst those
which do not exhaust the soil.
The plants of every former period are distin-
guished from those of the present, by the inconsi-
derable development of their roots. Fruit, leaves,
seeds, nearly every part of the plants of a former
world, except the roots, are found in the brown
coal formation. The vascular bundles, and the
perishable cellular tissue, of which then: roots con-
sisted, have been the first to suifer decomposition.
But when we examine oaks and other trees, which
in consequence of revolutions of the same kind oc-
curring in later ages have undergone the same
changes, we never find their roots absent.
The verdant plants of warm climates are very often
NOT INDISPENSABLE FOR PLANTS. 61
such as obtain from the soil only a point of attach-
ment and are not dependent on it for their growth.
How extremely small are the roots of the Cactus,
Sedum, and Sempervivum, in proportion to their
mass, and to the surface of their leaves ! Again, in
the most dry and barren sand, where it is impossible
for nourishment to be obtained through the roots,
we see the milky-juiced plants attain complete per-
fection. The moisture necessary for the nutrition
of these plants is derived from the atmosphere, and
when assimilated is secured from evaporation by
the nature of the juice itself. Caoutchouc and wax,
which are formed in these plants, surround the
water, as in oily emulsions, with an impenetrable
envelope by which the fluid is retained, in the same
manner as milk is prevented from evaporating, by
the skin which forms upon it. These plants, there-
fore, become turgid with their juices.
Particular examples might be cited of plants,
which have been brought to maturity, upon a small
scale, without the assistance of mould ; but fresh
proofs of the accuracy of our theory respecting the
origin of carbon would be superfluous and useless,
and could not render more striking, or more con-
vincing, the arguments already adduced. It must
not, however, be left unmentioned, that common
wood charcoal, by virtue merely of its ordinary well-
known properties, can completely replace vegetable
mould or humus. The experiments of Lukas, which
62 ORIGIN AND ACTION OF HUMUS.
are appended to this work, spare me all further
remarks upon its efficacy.
Plants thrive in powdered charcoal, and may be
brought to blossom and bear fruit if exposed to
the influence of the rain and the atmosphere ; the
charcoal may be previously heated to redness.
Charcoal is the most " indifferent " and most un-
changeable substance known ; it may be kept for
centuries without change, and is therefore not sub-
ject to decomposition. The only substances which
it can yield to plants are some salts, which it con-
tains, amongst which is silicate of potash. It is
known, however, to possess the power of condensing
gases within its pores, and particularly carbonic acid.
And it is by virtue of this power that the roots of
plants are supplied in charcoal exactly as in humus,
with an atmosphere of carbonic acid and air, which
is renewed as quickly as it is abstracted.
In charcoal powder, which had been used for
this purpose by Lukas for several years, Buchner
found a brown substance soluble in alkalies. This
substance was evidently due to the secretions from
the roots of the plants which grew in it.
A plant placed in a closed vessel in which the
air, and therefore the carbonic acid, cannot be
renewed, dies exactly as it would do in the vacuum
of an air-pump, or in an atmosphere of nitrogen or
carbonic acid, even though its roots be fixed in the
richest mould.
ASSIMILATION OF HYDROGEN. 63
Plants do not, however, attain maturity, under
ordinary circumstances, in charcoal powder, when
they are moistened with pure distilled water instead
of rain or river water. Rain water must, therefore,
contain within it one of the essentials of vegetable
life ; and it will be shown, that this is the presence of
a compound containing nitrogen, the exclusion of
which entirely deprives humus and charcoal of their
influence upon vegetation.
ON THE ASSIMILATION OF HYDROGEN.
The atmosphere contains the principal food of
plants in the form of carbonic acid, in the state,
therefore, of an oxide. The solid part of plants
(woody fibre) contains carbon and the constituents
of water, or the elements of carbonic acid together
with a certain quantity of hydrogen. We can con-
ceive the wood to arise from a combination of the
carbon of the carbonic acid with the elements of
water, under the influence of solar light. In this
case, 72*35 parts of oxygen, by weight, must be
separated as a gas for every 27*65 parts of carbon,
which are assimilated by a plant. Or, what is
much more probable, plants, under the same cir-
cumstances, may decompose water, the hydrogen
of which is assimilated along with carbonic acid,
whilst its oxygen is separated. If the latter change
takes place, 8*04 parts of hydrogen must unite with
100 parts of carbonic acid, in order to form woody
64 ASSIMILATION OF HYDROGEN.
fibre, and the 72'35 parts by weight of oxygen,
which was in combination with the hydrogen of the
water, and which exactly corresponds in quantity
with the oxygen contained in the carbonic acid,
must be separated in a gaseous form.
Each acre of land, which produces 8 centners or
cwts. of carbon, gives annually to the atmosphere
2600 Hessian Ibs. of free oxygen gas. The specific
weight of oxygen is expressed by the number
1*1026, hence 1 cubic metre of oxygen weighs 2*864
Hessian Ibs., and^ 2600 Ibs. of oxygen correspond
to 908 cubic metres or 58,112 Hessian cubic feet.
An acre of meadow, wood, or cultivated land in
general, replaces, therefore, in the atmosphere as
much oxygen as is exhausted by 8 centners of
carbon, either in its ordinary combustion in the
air or in the respiratory process of animals.
It has been mentioned at a former page that pure
woody fibre contains carbon and the component
parts of water, but that ordinary wood contains
more hydrogen than corresponds to this proportion.
This excess is owing to the presence of the green
principle of the leaf, wax, resin, and other bodies
rich in hydrogen. Water must be decomposed, in
order to furnish the excess of this element, and con-
sequently one equivalent of oxygen must be given
back to the atmosphere for every equivalent of
hydrogen appropriated by a plant to the production
of those substances. The quantity of oxygen, thus
BY THE DECOMPOSITION OF WATER. 65
set at liberty, cannot be insignificant, for the
atmosphere must receive 989 cubic feet of oxygen
for every pound of hydrogen assimilated.
It has already been stated, that a plant, in the
formation of woody fibre, must always yield to the at-
mosphere the same proportional quantity of oxygen ;
that the volume of this gas set free would be the
same whether it were due to the decomposition
of carbonic acid or of water. It was considered
most probable that the latter was the case.
From their generating caoutchouc, wax, fats, and
volatile oils containing hydrogen in large quantity,
and no oxygen, we may be certain that plants
possess the property of decomposing water, because
from no other body could they obtain the hydro-
gen of those matters. It has also been proved
by the observations of Humboldt on the fungi, that
water may be decomposed without the assimilation
of hydrogen. Water is a remarkable combination
of two elements, which have the power to separate
themselves from one another, in innumerable pro-
cesses, in a manner imperceptible to our senses ;
while carbonic acid, on the contrary, is only decom-
posable by violent chemical action.
Most vegetable structures contain hydrogen in
the form of water, which can be separated as such,
and replaced by other bodies ; but the hydrogen
which is essential to their constitution cannot pos-
sibly exist in the state of water.
All the hydrogen necessary for the formation of
F
66 ASSIMILATION OF HYDROGEN.
an organic compound is supplied to a plant by the
decomposition of water. The process of assimila-
tion, in its most simple form, consists in the
extraction of hydrogen from water, and carbon from
carbonic acid, in consequence of which, either all
the oxygen of the water and carbonic acid is sepa-
rated, as in the formation of caoutchouc, the
volatile oils which contain no oxygen, and other
similar substances, or only a part of it is exhaled.
The known composition of -the organic com-
pounds most generally present in vegetables,
enables us to state in definite proportions the
quantity of oxygen separated during their formation.
36 eq. carbonic acid and 22 eq. hydrogen derived ) _ ^ ,
from 22 eq. water . . .3
with the separation of 72 eq. oxygen.
36 eq. carbonic acid and 36 eq. hydrogen derived ? „
from 36 eq. water . . 3
with the separation of 72 eq. oxygen.
36 eq. carbonic acid and 30 eq. hydrogen derived > Starch
from 30 eq. water . . .3
with the separation of 72 eq. oxygen.
36 eq. carbonic acid and 16 eq. hydrogen derived > j, .
from 16 eq. water . . 3 ~~
with the separation of 64 eq. oxygen.
36 eq. carbonic acid and ,18 eq. hydrogen derived ) Tartaric Acid
from 18 eq. water . . 5 ~~
with the separation of 45 eq. oxygen.
36 eq. carbonic acid and 18 eq. hydrogen derived > Malic Acid
from 18 eq. water . . .3
with the separation of 54 eq. oxygen.
36 eq. carbonic acid and 24 eq. hydrogen derived > =Oil of Turpentine
from 24 eq. water . . .3
with the separation of 84 eq. oxygen.
It will readily be perceived that the formation of
ATTENDED WITH EVOLUTION OF OXYGEN. 6?
the acids is accompanied with the smallest separa-
tion of oxygen ; that the amount of oxygen set free
increases with the production of the so-named
neutral substances, and reaches its maximum in the
formation of the oils. Fruits remain acid in cold
summers ; while the most numerous trees under the
tropics are those which produce oils, caoutchouc,
and other substances, containing very little oxygen.
The action of sunshine and influence of heat, upon
the ripening of fruit, is thus in a certain measure
represented by the numbers above cited.
The green resinous principle of the leaf dimi-
nishes in quantity, while oxygen is absorbed, when
fruits are ripened in the dark; red and yellow
colouring matters are formed ; tartaric, citric, and
tannic acids disappear, and are replaced by sugar,
amylin, or gum. 6 eq. Tartaric Add) by absorb-
ing 6 eq. oxygen from the air, form Grape
Sugar, with the separation of 12 eq. carbonic
acid. 1 eq. Tannic Avid, by absorbing 8 eq.
oxygen from the air, and 4 eq. water form 1 eq.
of Amylin, or starch, with separation of 6 eq.
carbonic acid.
We can explain, in a similar manner, the forma-
tion of all the component substances of plants,
which contain no nitrogen, whether they are pro-
duced from carbonic acid and water, with separation
of oxygen, or by the conversion of one substance
into the other, by the assimilation of oxygen and
separation of carbonic acid. We do not know in
F2
68 ASSIMILATION OF HYDROGEN.
what form the production of these constituents
takes place ; in this respect, the representation of
their formation which we have given must not
be received in an absolute sense, it being intended
only to render the nature of the process more
capable of apprehension ; but it must not be for-
gotten, that if the conversion of tartaric acid into
sugar, in grapes, be considered as a fact, it must
take place under all circumstances in the same
proportions.
The vital process in plants is, with reference to
the point we have been considering, the very
reverse of the chemical processes engaged in the
formation of salts. Carbonic acid, zinc, and water,
when brought into contact, act upon one another,
and hydrogen is separated, while a white pulveru-
lent compound is formed, which contains carbonic
acid, zinc, and the oxygen of the water. A living
plant represents the zinc in this process : but the
process of assimilation gives rise to compounds,
which contain the elements of carbonic acid and
the hydrogen of water, whilst oxygen is separated.
Decay has been described above as the great
operation of nature, by which that oxygen, which
was assimilated by plants during life, is again
returned to the atmosphere. During the progress
of growth, plants appropriate carbon in the form of
carbonic acid, and hydrogen from the decomposi-
tion of water, the oxygen of which is set free,
together with a part or all of that contained in the
SOURCE OF THE NITROGEN OF PLANTS. 69
carbonic acid. In the process of putrefaction,, a
quantity of water, exactly corresponding to that of
the hydrogen, is again formed by extraction of
oxygen from the air ; while all the oxygen of the
organic matter is returned to the atmosphere in the
form of carbonic acid. Vegetable matters can emit
carbonic acid, during their decay, only in propor-
tion to the quantity of oxygen which they contain ;
acids, therefore, yield more carbonic acid than
neutral compounds ; while fatty acids, resin, and
wax, do not putrify, they remain in the soil without
any apparent change.
The numerous springs which emit carbonic acid
in the neighbourhood of extinct volcanoes, must be
regarded as another considerable source of oxygen.
Bischof calculated that the springs of carbonic acid
in the Eifel (a volcanic district near Coblenz) send
into the air every day more than 90,000 Ibs. of car-
bonic acid, corresponding to 64,800 Ibs. of pure
oxygen.
ON THE ORIGIN AND ASSIMILATION OF
NITROGEN.
We cannot suppose that a plant would attain
maturity, even in the richest vegetable mould, with-
out the presence of matter containing nitrogen ;
since we know that nitrogen exists in every part
of the vegetable structure. The first and most
important question to be solved, therefore, is :
How and in what form does nature furnish
70 SOURCE AND ASSIMILATION
nitrogen to vegetable albumen, and gluten., to fruits
and seeds ?
This question is susceptible of a very simple
solution.
Plants, as we know, grow perfectly well in pure
charcoal, if supplied at the same time with rain-
water. Rain-water can contain nitrogen only in two
forms, either as dissolved atmospheric air, or as am-
monia. Now, the nitrogen of the air cannot be made
to enter into combination with any element except
oxygen, even by employment of the most powerful
chemical means. We have not the slightest reason
for believing that the nitrogen of the atmosphere
takes part in the processes of assimilation of plants
and animals ; on the contrary, we know that many
plants emit the nitrogen, which is absorbed by their
roots, either in the gaseous form, or in solution in
water. But there are on the other hand numerous
facts, showing, that the formation in plants of
substances containing nitrogen, such as gluten,
takes place in proportion to the quantity of this
element which is conveyed to their roots in the
staje of ammonia, derived from the putrefaction of
animal matter.
Ammonia, too, is capable of undergoing such a
multitude of transformations, when in contact with
other bodies, that in this respect it is not inferior to
water, which possesses the same property in an emi-
nent degree. It possesses properties which we do
not find in any other compound of nitrogen ; when
OF THE NITROGEN OF PLANTS. 71
pure, it is extremely soluble in water ; it forms
soluble compounds with all the acids ; and when in
contact with certain other substances, it completely
resigns its character as an alkali, and is capable of
assuming the most various and opposite forms.
Formate of ammonia changes, under the influence
of a high temperature, into hydrocyanic acid and
water, without the separation of any of its elements.
Ammonia forms urea, with cyanic acid, and a
series of crystalline compounds, with the volatile
oils of mustard and bitter almonds. It changes
into splendid blue or red colouring matters, when in
contact with the bitter constituent of the bark of
the apple-tree (phloridzin), with the sweet prin-
ciple of the Variolaria dealbata (ordn), or with the
tasteless matter of the Rocella tinctoria (erythrin).
All blue colouring matters which are reddened by
acids, and all red colouring substances which are
rendered blue by alkalies, contain nitrogen, but not
in the form of a base.
These facts are not sufficient to establish the
opinion that it is ammonia, which affords all vege-
tables without exception the nitrogen which enters
into the composition of their constituent substances.
Considerations of another kind, however, give to
this opinion a degree of certainty, which completely
excludes all other views of the matter.
Let us picture to ourselves the condition of a
well- cultured farm, so large as to be independent of
assistance from other quarters. On this extent of
72 SOURCE AND ASSIMILATION
land there is a certain quantity of nitrogen con-
tained both in the corn and fruit which it produces,
and in the men and animals which feed upon them,
and also in their excrements. We shall suppose
this quantity to be known. The land is cultivated
without the importation of any foreign substance
containing nitrogen. Now, the products of this farm
must be exchanged every year for money, and other
necessaries of life, for bodies therefore which contain
no nitrogen. A certain proportion of nitrogen is
exported with corn and cattle ; and this exportation
takes place every year, without the smallest com-
pensation ; yet after a given number of years, the
quantity of nitrogen will be found to have increased.
Whence, we may ask, comes this increase of nitro-
gen ? The nitrogen in the excrements cannot repro-
duce itself, and the earth cannot yield it. Plants,
and consequently animals, must, therefore, derive
their nitrogen from the atmosphere.
It will in a subsequent part of this work be shown
that the last products of the decay and putrefaction
of animal bodies present themselves in two different
forms. They are in the form of a combination of
hydrogen and nitrogen — ammonia, in the temperate
and cold climates, and in that of a compound, con-
taining oxygen, nitric acid, in the tropics and hot
climates. The formation of the latter is preceded
by the production of the first. Ammonia is the
last product of the putrefaction of animal bodies ;
nitric acid is the product of the transformation of
OF THE NITROGEN OF PLANTS. 73
ammonia. A generation of a thousand million
men is renewed every thirty years : thousands of
millions of animals cease to live, and are repro-
duced, in a much shorter period. Where is the
nitrogen which they contained during life ? There
is no question which can be answered with more
positive certainty. All animal bodies, during their
decay, yield the nitrogen, which they contain, to
the atmosphere, in the form of ammonia. Even
in the bodies buried sixty feet under ground in the
churchyard of the Eglise des Innocens, at Paris, all
the nitrogen contained in the adipocire was in the
state of ammonia. Ammonia is the simplest of all
the compounds of nitrogen ; and hydrogen is the ele-
ment for which nitrogen possesses the most powerful
affinity.
The nitrogen of putrified animals is contained in
the atmosphere as ammonia, in the form of a gas
which is capable of entering into combination with
carbonic acid, and of forming a volatile salt. Am-
monia in its gaseous form as well as all its volatile
compounds are of extreme solubility in water.
Ammonia, therefore, cannot remain long in the
atmosphere, as every shower of rain must condense
it, and convey it to the surface of the earth.
Hence, also, rain-water must, at all times, contain
ammonia, though not always in equal quantity.
It must be greater in summer than in spring or
in winter, because the intervals of time between
the showers are in summer greater; and when
74 SOURCE AND ASSIMILATION
several wet days occur, the rain of the first must
contain more of it than that of the second. The
rain of a thunder-storm, after a long protracted
drought, ought for this reason to contain the
greatest quantity, which is conveyed to the earth
at one time.
But all the analyses of atmospheric air, hitherto
made, have failed to demonstrate the presence of am-
monia, although according to our view it can never
be absent. Is it possible that it 'could have escaped
our most delicate and most exact apparatus ? The
quantity of nitrogen contained in a cubic foot of
air is certainly extremely small, but notwithstand-
ing this, the sum of the quantities of nitrogen from
thousands and millions of dead animals is more than
sufficient to supply all those living at one time with
this element.
From the tension of aqueous vapour at 15° C.
(59° F.) = 6,98 lines (Paris measure) and from its
known specific gravity at 0° C. (32° F.), it follows
that when the temperature of the air is 59° F. and
the height of the barometer 28", 1 cubic metre or
64 Hessian cubic feet of aqueous vapour are con-
tained in 487 cubic metres, or 31,168 cubic feet
of air ; 64 cubic feet of aqueous vapour weigh
about 1^ Ib. Consequently if we suppose that the
air saturated with moisture at 59° F. allows all
the water which it contains in the gaseous form
to fall as rain ; then 1 Hessian pound of rain-
water must be obtained from every 20,800 cubic
OF THE NITROGEN OF PLANTS. 75
feet of air. The whole quantity of ammonia
contained in the same number of cubic feet will
also be returned to the earth in this one pound
of rain-water. But if the 20,800 cubic feet of
air contain a single grain of ammonia, then
ten cubic inches, the quantity usually employed
in an analysis, must contain only 0.000000048
of a grain. This extremely small proportion
is absolutely inappreciable by the most delicate
and best eudiometer ; it might be classed among
the errors of observation, even were its quan-
tity ten thousand times greater. But the de-
tection of ammonia must be much more easy,
when a pound of rain-water is examined, for this
contains all the gas that was diffused through
20,800 cubic feet of air.
If a pound of rain-water contain only ^th of a
grain of ammonia, then a field of 40,000 square feet
must receive annually upwards of 80 Ibs. of ammo-
nia, or 65 Ibs. of nitrogen ; for, by the observations
of ScMbler, which were formerly alluded to, about
700,000 Ibs. of rain fall over this surface in four
months, and consequently the annual fall must be
2,500.000 Ibs. This is much more nitrogen than
is contained in the form of vegetable albumen and
gluten, in 2650 Ibs. of wood, 2800 Ibs. of hay, or
200 cwt. of beet-root, which are the yearly produce
of such a field, but it is less than the straw, roots,
and grain of corn which might grow on the same
surface, would contain.
76 SOURCE AND ASSIMILATION
Experiments, made in this laboratory (Giessen)
with the greatest care and exactness, have placed
the presence of ammonia in rain-water beyond all
doubt. It has hitherto escaped observation, be-
cause no person thought of searching for it. All
the rain-water employed in this inquiry was col-
lected 600 paces south-west of Giessen, whilst the
wind was blowing in the direction of the town.
When several hundred pounds of it were distilled
in a copper still, and the first two or three pounds
evaporated with the addition of a little muriatic
acid, a very distinct crystallisation of sal-ammoniac
was obtained : the crystals had always a brown or
yellow colour.
Ammonia may likewise be always detected in
snow-water. Crystals of sal-ammoniac were ob-
tained by evaporating in a vessel with muriatic
acid several pounds of snow, which were gathered
from the surface of the ground in March, when the
snow had a depth of 10 inches. Ammonia was set
free from these crystals by the addition of hydrate
of lime. The inferior layers of snow, which rested
upon the ground, contained a quantity decidedly
greater than those which formed the surface.
It is worthy of observation, that the ammonia
contained in rain and snow water, possessed an
offensive smell of perspiration and animal excre-
ments,— a fact which leaves no doubt respecting
its origin.
Hilnefeld has proved, that all the springs in
OF THE NITROGEN OF PLANTS. 77
Greifswalde, Wick, Eldena, and Kostenhagen, con-
tain carbonate and nitrate of ammonia. Ammo-
niacal salts have been discovered in many mineral
springs in Kissingen and other places. The am-
monia of these salts can only arise from the atmo-
sphere.
Any one may satisfy himself of the presence of
ammonia in rain, by simply adding a little sulphuric
or muriatic acid to a quantity of rain-water, and
evaporating this nearly to dryness in a clean porce-
lain basin. The ammonia remains in the residue,
in combination with the acid employed ; and may
be detected either by the addition of a little chloride
of platinum, or more simply by a little powdered
lime, which separates the ammonia, and thus
renders its peculiar pungent smell sensible. The
sensation which is perceived upon moistening
the hand with rain-water, so different from that
produced by pure distilled water, and to which the
term softness is vulgarly applied, is also due to the
carbonate of ammonia contained in the former.
The ammonia, which is removed from the atmo-
sphere by rain and other causes, is as constantly
replaced by the putrefaction of animal and vegeta-
ble matters. A certain portion of that which falls
with the rain, evaporates again with the water, but
another portion is,we suppose, taken up by the roots
of plants, and entering into new combinations in
the different organs of assimilation, produces albu-
men, gluten, quinine, morphia, cyanogen, and a
78 SOURCE AND ASSIMILATION
number of other compounds containing nitrogen.
The chemical characters of ammonia render it ca-
pable of entering into such combinations, and of
undergoing numerous transformations. We have
now only to consider whether it really is taken up
in the form of ammonia by the roots of plants, and
in that form applied by their organs to the produc-
tion of the azotised matters contained in them.
This question is susceptible of easy solution by well-
known facts.
In the year 1834, I was engaged with Dr. Wil-
brand, professor of botany in the university of
Giessen, in an investigation respecting the quantity
of sugar contained in different varieties of maple-
trees, which grew upon soils which were not ma-
nured. We obtained crystallised sugars from all,
by simply evaporating their juices, without the ad-
dition of any foreign substance ; and we unexpect-
edly made the observation, that a great quantity of
ammonia was emitted from this juice, when mixed
with lime, and also from the sugar itself during its
refinement. The vessels, which hung upon the
trees in order to collect the juice, were watched
with greater attention, on account of the suspicion
that some evil-disposed persons had introduced urine
into them, but still a large quantity of ammonia was
again found in the form of neutral salts. The juice
had no colour, and had no reaction on that of
vegetables. Similar observations were made upon
the juice of the birch-tree ; the specimens subjected
OF THE NITROGEN OF PLANTS. 79
to experiment were taken from a wood several miles
distant from any house, and yet the clarified juice,
evaporated with lime, emitted a strong odour of
ammonia.
In the manufactories of beet-root sugar, many
thousand cubic feet of juice are daily purified with
lime, in order to free it from vegetable albumen and
gluten, and it is afterwards evaporated for crystal-
lization. Every person, who has entered such a
manufactory, must have been astonished at the
great quantity of ammonia which is volatilised along
with the steam. This ammonia must be contained in
the form of an ammoniacal salt, because the neutral
juice possesses the same characters as the solution
of such a salt in water ; it acquires, namely, an acid
reaction during evaporation, in consequence of the
neutral salt being converted by loss of ammonia
into an acid salt. The free acid which is thus
formed is a source of loss to the manufacturers of
sugar from beet-root, by changing a part of the
sugar into uncrystallisable grape sugar and syrup.
The products of the distillation of flowers, herbs,
and roots, with water, and all extracts of plants
made for medicinal purposes, contain ammonia. The
unripe, transparent and gelatinous pulp of the
almond and peach emit much ammonia when treated
with alkalies. (RoUquet.) The juice of the fresh
tobacco leaf contains ammoniacal salts. The water,
which exudes from a cut vine, when evaporated with
a few drops of muriatic acid, also yields a gummy
80 SOURCE AND ASSIMILATION
deliquescent mass, which evolves much ammonia
on the addition of lime. Ammonia exists in every
part of plants, in the roots (as in beet-root), in the
stem (of the maple-tree), and in all blossoms and
fruit in an unripe condition.
The juices of the maple and birch contain both
sugar and ammonia, and therefore afford all the
conditions necessary for the formation of the azo-
tised components of the branches, blossoms, and
leaves, as well as of those which contain no azote
or nitrogen. In proportion as the development
of those parts advances, the ammonia diminishes
in quantity, and when they are fully formed, the
tree yields no more juice.
The employment of animal manure in the culti-
vation of grain, and the vegetables which serve for
fodder to cattle, is the most convincing proof that
the nitrogen of vegetables is derived from ammonia.
The quantity of gluten in wheat, rye, and barley,
is very different ; these kinds of grain also, even
when ripe, contain this compound of nitrogen in
very different proportions. Proust found French
wheat to contain 12.5 per cent.. of gluten; Vogel
found that the Bavarian contained 24 per cent. ;
Davy obtained 19 per cent, from winter, and 24
from summer wheat ; from Sicilian 21, and from
Barbary wheat 19 per cent. The meal of Alsace
wheat contains, according to Boussingault, 17.3 per
cent, of gluten ; that of wheat grown in the " Jar-
din des Plantes" 26.7, and that of winter wheat
OF THE NITROGEN OF PLANTS. 81
3*33 per .cent. Such great differences must be
owing to some cause, and this we find in the different
methods of cultivation. An increase of animal manure
gives rise not only to an increase in the number of
seeds, but also to a most remarkable difference in
the proportion of the gluten which they contain.
Animal manure, as we shall afterwards show, acts
only by the formation of ammonia. One hundred
parts of wheat grown on a soil manured with cow-
dung (a manure containing the smallest quantity of
nitrogen), afforded only 11*95 parts of gluten, and
64*34 parts of amylin, or starch ; whilst the same
quantity, grown on a soil manured with human urine,
yielded the maximum of gluten, namely 35*1 per
cent. Putrified urine contains nitrogen in the forms
of carbonate, phosphate, and lactate of ammonia,
and in no other form than that of ammoniacal salts.
" Putrid urine is employed in Flanders as a
manure with the best results. During the putre-
faction of urine, ammoniacal salts are formed in large
quantity, it may be said exclusively ; for under the
influence of heat and moisture urea, the most pro-
minent ingredient of the urine, is converted into
carbonate of ammonia. The barren soil on the
coast of Peru is rendered fertile by means of a manure
called Guano, which is collected from several islands
on the South Sea.* It is sufficient to add a small
* The guano, which forms a stratum several feet in thickness upon the
surface of these islands, consists of the putrid excrements of innumera-
ble sea-fowl that remain on them during the breeding season.
G
82 SOURCE AND ASSIMILATION
quantity of guano to a soil, which consists only of
sand and clay, in order to procure the richest crop
of maize. The soil itself does not contain the
smallest particle of organic matter, and the manure
employed is formed only of ur ate, phosphate, oxalate,
and carbonate of ammonia, together with a few
earthy salts. "*
Ammonia, therefore, must have yielded the nitro-
gen to these plants. Gluten is obtained not only
from corn, but also from grapes -and other plants ;
but that extracted from the grapes is called vege-
table albumen, although it is identical in composi-
tion and properties with the ordinary gluten.
It is ammonia which yields nitrogen to the vege-
table albumen, the principal constituent of plants ;
and it must be ammonia which forms the red and
blue colouring matters of flowers. Nitrogen is not
presented to wild plants in any other form capable
of assimilation. Ammonia, by its transformation,
furnishes nitric acid to the tobacco plant, sun-
flower, Chenopodium, and Borago qfficinalis, when
they grow in a soil completely free from nitre.
Nitrates are necessary constituents of these plants,
which thrive only when ammonia is present in
large quantity, and when they are also subject to
the influence of the direct rays of the sun, an influ-
ence necessary to effect the disengagement within
their stem and leaves of the oxygen, which shall
unite with the ammonia to form nitric acid.
* Boussingault, Ann. de Ch. et de Phys. Ixv. p. 319.
OF THE NITROGEN OF PLANTS. 83
The urine of men and of carnivorous animals
contains a large quantity of nitrogen, partly in the
form of phosphates, partly as urea. Urea is con-
verted during putrefaction into carbonate of am-
monia,, that is to say, it takes the form of the very
salt which occurs in rain-water. Human urine is
the most powerful manure for all vegetables con-
taining nitrogen ; that of horses and horned cattle
contains less of this element, but infinitely more
than the solid excrements of these animals. In
addition to urea, the urine of herbivorous animals
contains hippuric acid, which is decomposed during
putrefaction into benzoic acid and ammonia. The
latter enters into the composition of the gluten, but
the benzoic acid often remains unchanged : for
example, in the Anthoxanthum odoratum.
The solid excrements of animals contain compa-
ratively very little nitrogen, but this could not be
otherwise. The food taken by animals supports
them only in so far as it offers elements for assimi-
lation to the various organs, which they may require
for their increase or renewal. Corn, grass, and
all plants, without exception, contain azotised
substances. The quantity of food, which animals
take for their nourishment, diminishes or increases
in the same proportion, as it contains more or less
of the substances containing nitrogen. A horse may
be kept alive by feeding it with potatoes, which
contain a very small quantity of nitrogen ; but life
thus supported is a gradual starvation ; the animal
G2
84 SOURCE AND ASSIMILATION
increases neither in size nor strength, and sinks
under every exertion. The quantity of rice which
an Indian eats astonishes the European ; but the
fact, that rice contains less nitrogen than any other
kind of grain at once explains the circumstance.
Now, as it is evident that the nitrogen of the
plants and seeds used by animals as food must be
employed in the process of assimilation, it is natural
to expect that the excrements of these animals will
be deprived of it, in proportion to the perfect diges-
tion of the food, and can only contain it when
mixed with secretions from the liver and intestines.
Under all circumstances, they must contain less
nitrogen than the food. When, therefore, a field is
manured with animal excrements, a smaller quan-
tity of matter containing nitrogen is added to it than
has been taken from it in the form of grass, herbs,
or seeds. By means of manure, an addition only is
made to the nourishment which the air supplies.
In a scientific point of view, it should be the care
of the agriculturist so to employ all the substances
containing a large proportion of nitrogen which his
farm affords in the form of animal excrements, that
they shall serve as nutriment to his own plants.
This will not be the case unless those substances
are properly distributed upon his land. A heap of
manure lying unemployed upon his land would
serve him no more than his neighbours. The
nitrogen in it would escape as carbonate of ammo-
nia into the atmosphere, and a mere carbonaceous
OP THE NITROGEN OF PLANTS. 85
residue of decayed plants would, after some years,
be found in its place.
All animal excrements emit carbonic acid and am-
monia, as long as nitrogen exists in them. In every
stage of their putrefaction an escape of ammonia
from them may be induced by moistening them
with a potash ley ; the ammonia being apparent
to the senses by a peculiar smell, and by the dense
white vapour which arises when a solid body moist-
ened with an acid is brought near it. This ammo-
nia evolved from manure is imbibed by the soil
either in solution in water, or in the gaseous form,
and plants thus receive a larger supply of nitrogen
than is afforded to them by the atmosphere.
But it is much less the quantity of ammonia,
yielded to a soil by animal excrements, than the
form in which it is presented by them, that causes
their great influence on its fertility. Wild plants
obtain more nitrogen from the atmosphere in the
form of ammonia than they require for their growth,
for the water which evaporates through their leaves
and blossoms, emits, after some time, a putrid smell,
a peculiarity possessed only by such bodies as
contain nitrogen. Cultivated plants receive the
same quantity of nitrogen from the atmosphere as
trees, shrubs, and other wild plants ; but this is
not sufficient for the purposes of agriculture.
Agriculture differs essentially from the cultivation
of forests, inasmuch as its principal object consists
in the production of nitrogen under any form capa-
86 SOURCE AND ASSIMILATION
ble of assimilation ; whilst the object of forest
culture is confined principally to the production of
carbon. All the various means of culture are sub-
servient to these two main purposes. A part only
of the carbonate of ammonia, which is conveyed by
rain to the soil is received by plants, because a
certain quantity of it is volatilised with the vapour
of water ; only that portion of it can be assimilated
which sinks deeply into the soil, or which is con-
veyed directly to the leaves by dew, or is absorbed
from the air along with the carbonic acid.
Liquid animal excrements, such as the urine with
which the solid excrements are impregnated, con-
tain the greatest part of their ammonia in the state
of salts, in a form, therefore, in which it has com-
pletely lost its volatility when presented in this
condition ; not the smallest portion of the am-
monia is lost to the plants, it is all dissolved by
water, and imbibed by their roots. The evident
influence of gypsum upon the growth of grasses —
the striking fertility and luxuriance of a meadow
upon which it is strewed — depends only upon its
fixing in the soil the ammonia of the atmosphere,
which would otherwise be volatilised, with the
water which evaporates. The carbonate of ammo-
nia contained in rain-water is decomposed by
gypsum, in precisely the same manner as in the
manufacture of sal-ammoniac. Soluble sulphate
of ammonia and carbonate of lime are formed ; and
this salt of ammonia possessing no volatility is con-
OF THE NITROGEN OF PLANTS. 87
sequently retained in the soil. All the gypsum
gradually disappears, but its action upon the car-
bonate of ammonia continues as long as a trace of
it exists.
The beneficial influence of gypsum and of many
other salts has been compared to that of aromatics,
which increase the activity of the human stomach
and intestines, and give a tone to the whole system.
But plants contain no nerves ; we know of no sub-
stance capable of exciting them to intoxication and
madness, or of lulling them to sleep and repose.
No substance can possibly cause their leaves to
appropriate a greater quantity of carbon from the
atmosphere, when the other constituents which the
seeds, roots, and leaves require for their growth are
wanting. The favourable action of small quantities
of aromatics upon man, when mixed with his food, is
undeniable, but aromatics are given to plants with-
out food to be digested, and still they flourish with
greater luxuriance.
It is quite evident, therefore, that the common
view concerning the influence of certain salts upon
the growth of plants evinces only ignorance of its
cause.
The action of gypsum or chloride of calcium really
consists in their giving a fixed condition to the
nitrogen — or ammonia which is brought into the
soil, and which is indispensable for the nutrition of
plants.
In order to form a conception of the effect of
88 SOURCE AND ASSIMILATION
gypsum, it may be sufficient to remark that 100
Hess. Ibs. of burned gypsum fixes as much ammo-
nia in the soil as 6250 Ibs. of horses' urine * would
yield to it, even on the supposition that all the
nitrogen of the urea and hippuric acid were absorbed
by the plants without the smallest loss, in the form
of carbonate of ammonia. If we admit with Bous-
singault-f- that the nitrogen in grass amounts to
Too of its weight, then every pound of nitrogen
which we add increases the produce of the mea-
dow 100 Ibs., and this increased produce of 100 Ibs.
is effected by the aid of a little more than 4 Ibs. of
gypsum.
Water is absolutely necessary to effect the de-
composition of the gypsum, on account of its diffi-
cult solubility, (1 part of gypsum requires 400 parts
of water for solution,) and also to assist in the ab-
sorption of the sulphate of ammonia by the plants :
hence it happens, that the influence of gypsum is
not observable on dry fields and meadows.
The decomposition of gypsum by carbonate of
ammonia does not take place instantaneously ; on
the contrary, it proceeds very gradually, and this
* The urine of the horse contains, according to Fourcroy and Vau-
quelin, in 1 000 parts,
Urea 7 parts.
Hippurate of soda . . 24 „
Salts and water . . 979 „
1000 parts,
t Boussingault, Ann. de Ch. et de Phys. t. Ixiii. page 243.
OP THE NITROGEN OF PLANTS. 89
explains why the action of the gypsum lasts for
several years.
The advantage of manuring fields with burned
clay and the fertility of ferruginous soils, which
have been considered as facts so incomprehensible,
may be explained in an equally simple manner.
They have been ascribed to the great attraction for
water, exerted by dry clay and ferruginous earth ;
but common dry arable land possesses this property
in as great a degree : and besides, what influence
can be ascribed to a hundred pounds of water spread
over an acre of land, in a condition in which it can-
not be serviceable either by the roots or leaves ?
The true cause is this : —
The oxides of iron and alumina are distinguished
from all other metallic oxides by their power of
forming solid compounds with ammonia. The pre-
cipitates obtained by the addition of ammonia to
salts of alumina or iron are true salts, in which the
ammonia is contained as a base. Minerals contain-
ing alumina or oxide of iron also possess, in an
eminent degree, the remarkable property of attract-
ing ammonia from the atmosphere and of retaining
it. Vauquelin, whilst engaged in the trial of a cri-
minal case, discovered that all rust of iron contains
a certain quantity of ammonia. Chevalier after-
wards found that ammonia is a constituent of all
minerals containing iron ; that even hematite, a
mineral which is not at all porous, contains one per
cent, of it. Bouis showed also, that the peculiar
90 SOURCE AND ASSIMILATION
odour observed on moistening minerals containing
alumina, is partly owing to their exhaling ammonia.
Indeed^ gypsum and some varieties of alumina,
pipe-clay for example, emit so much ammonia,
when moistened with caustic potash, that even after
they have been exposed for two days, litmus paper
held over them becomes blue. Soils, therefore, which
contain oxides of iron, and burned clay, must ab-
sorb ammonia, an action which is favoured by their
porous condition ; they further- prevent the escape
of the ammonia once absorbed by their chemical
properties. Such soils in fact act precisely as a
mineral acid would do, if extensively spread over
their surface ; with this difference, that the acid
would penetrate the ground, enter into combination
with lime, alumina, and other bases, and thus lose,
in a few hours, its property of absorbing ammonia
from the atmosphere.
The ammonia absorbed by the clay or ferrugi-
nous oxides is separated by every shower of rain,
and conveyed in solution to the soil.
Powdered charcoal possesses a similar action, but
surpasses all other substances in the power which
it possesses of condensing ammonia within its pores,
particularly when it has been previously heated to
redness. Charcoal absorbs 90 times its volume of
ammoniacal gas, which may be again separated by
simply moistening it with water. (De Saussure.)
Decayed wood approaches very nearly to charcoal in
this power ; decayed oak wood absorbs 72 times its
OF THE NITROGEN OF PLANTS. 91
volume, after having been completely dried under
the air-pump. We have here an easy and
satisfactory means of explaining still further
the properties of humus, or wood in a decaying
state. It is not only a slow and constant source
of carbonic acid, but it is also a means by
which the necessary nitrogen is conveyed to
plants.
Nitrogen is found in lichens, which grow on
basaltic rocks. Our fields produce more of it than
we have given them as manure, and it exists in all
kinds of soils and minerals which were never in
contact with organic substances. The nitrogen in
these cases could only have been extracted from the
atmosphere.
We find this nitrogen in the atmosphere in rain-
water and in all kinds of soils, in the form of am-
monia, as a product of the decay and putrefaction
of preceding generations of animals and vegetables.
We find likewise that the proportion of azotised
matters in plants is augmented by giving them a
larger supply of ammonia conveyed in the form of
animal manure.
No conclusion can then have a better foundation
than this, that it is the ammonia of the atmosphere
which furnishes nitrogen to plants.
Carbonic acid, water and ammonia, contain the
elements necessary for the support of animals and
vegetables. The same substances are the ultimate
products of the chemical processes of decay and
92 OF THE INORGANIC
putrefaction. All the innumerable products of
vitality resume, after death, the original form from
which they sprung. And thus death — the complete
dissolution of an existing generation — becomes the
source of life for a new one.
But another question arises, — Are the conditions
already considered the only ones necessary for the
life of vegetables ? It will now be shown that they
are not.
OF THE INORGANIC CONSTITUENTS OF PLANTS.
Carbonic acid, water and ammonia, are necessary
for the existence of plants, because they contain
the elements from which their organs are formed ;
but other substances are likewise requisite for the
formation of certain organs destined for special
functions peculiar to each family of plants. Plants
obtain these substances from inorganic nature. In
the ashes left after the incineration of plants, the
same substances are formed although in a changed
condition.
Many of these inorganic constituents vary ac-
cording to the soil in which the plants grow, but a
certain number of them are indispensable to their
development. All substances in solution in a soil
are absorbed by the roots of plants, exactly as a
sponge imbibes a liquid, and all that it contains,
without selection. The substances thus conveyed
to plants are retained in greater or less quan-
CONSTITUENTS OF PLANTS. 93
tity, or are entirely separated when not suited for
assimilation.
Phosphate of magnesia in combination with am-
monia is an invariable constituent of the seeds of
all kinds of grasses. It is contained in the outer
horny husk, and is introduced into bread along with
the flour, and also into beer. The bran of flour
contains the greatest quantity of it. It is this salt
which forms large crystalline concretions, often
amounting to several pounds in weight, in the
caecum of horses belonging to millers ; and when
ammonia is mixed with beer, the same salt sepa-
rates as a white precipitate.
Most plants, perhaps all of them, contain organic
acids of very different composition and properties,
all of which are in combination with bases, such as
potash, soda, lime or magnesia. These bases evi-
dently regulate the formation of the acids, for the
diminution of the one is followed by a decrease of
the other : thus, in the grape, for example, the
quantity of potash contained in its juice is less,
when it is ripe, than when unripe ; and the acids,
under the same circumstances, are found to vary
in a similar manner. Such constituents exist in
small quantity in those parts of a plant in which
the process of assimilation is most active, as in the
mass of woody fibre ; and their quantity is greater
in those organs, whose office it is to prepare sub-
stances conveyed to them for assimilation by other
parts. The leaves contain more inorganic matters
94 OF THE INORGANIC
than the branches., and the branches more than
the stem. The potato plant contains more potash
before blossoming than after it.
The acids found in the different families of plants
are of various kinds ; it cannot be supposed that
their presence and peculiarities are the result of
accident. The fumaric and oxalic acids in the
liverwort^ the kinovic acid in the China nova, the
rocellic acid in the Rocella tinctoria, the tartaric
acid in grapes, and the numerous other organic
acids, must serve some end in vegetable life. But
if these acids constantly exist in vegetables^ and are
necessary to their life, which is incontestable, it is
equally certain that some alkaline base is also in-
dispensable in order to enter into combination with
the acids which are always found in the state of
salts. All plants yield by incineration ashes con-
taining carbonic acid ; all therefore must contain
salts of an organic acid.
Now, as we know the capacity of saturation of
organic acids to be unchanging, it follows that the
quantity of the bases united with them cannot vary,
and for this reason the latter substances ought to
be considered with the strictest attention both by
the agriculturist and physiologist.
We have no reason to believe that a plant in a
condition of free and unimpeded growth produces
more of its peculiar acids than it requires for its
own existence ; hence, a plant, on whatever soil it
grows, must contain an invariable quantity of alka-
CONSTITUENTS OF PLANTS. 95
line bases. Culture alone will be able to cause a
deviation.
In order to understand this subject clearly, it
will be necessary to bear in mind, that any one of
the alkaline bases may be substituted for another,
the action of all being the same. Our conclusion
is, therefore, by no means endangered by the exist-
ence of a particular alkali in one plant, which may
be absent in others of the same species. If this
inference be correct, the absent alkali or earth must
be supplied by one similar in its mode of action, or
in other words, by an equivalent of another base.
The number of equivalents of these various bases,
which may be combined with a certain portion of
acid, must necessarily be the same, and, therefore,
the amount of oxygen contained in them must
remain unchanged, under all circumstances, and on
whatever soil they grow.
Of course, this argument refers only to those
alkaline bases, which in the form of organic salts
form constituents of the plants. Now, these salts
are preserved in the ashes of plants, as carbonates,
the quantity of which can be easily ascertained.
It has been distinctly shown by the analyses of De
Saussure and Berthier, that the nature of a soil exer
cises a decided influence on the quantity of the dif-
ferent metallic oxides contained in the plants, which
grow on it ; that magnesia, for example, was con-
tained in the ashes of a pine-tree grown at Mont
Breven, whilst it was absent from the ashes of a tree
96 OF THE INORGANIC
of the same species from Mont La Salle,and that even
the proportion of lime and potash was very different.
Hence it has been concluded (erroneously, I
believe), that the presence of bases exercises no
particular influence upon the growth of plants ; but
even were this view correct, it must be considered
as a most remarkable accident, that these same
analyses furnish proof for the very opposite opinion.
For although the composition of the ashes of these
pine-trees was so very different, they contained,
according to the analysis of De Saussure, an equal
number of equivalents of metallic oxides ; or what is
the same thing, the quantity of oxygen contained
in all the bases was in both cases the same.
100 parts of the ashes of the pine-tree from Mont
Breven contained*: —
Carbonate of Potash . 3-60 Quantity of oxygen in the Potash 0-4 1
„ Lime . 46-34 „ „ „ Lime 7-33
6-77 „ „ „ Magnesia 1'27
Sum of the carbonates 56-71 Sum of the oxygen in the bases 9-01
100 parts of the ashes of the pine from Mont La
Salle contained-}-: —
Carbonate of Potash . 7-36 Quantity of oxygen in the Potash 085
„ Lime . 51-19 „ „ „ Lime 8-10
„ Magnesia 00 -00
Sum of the carbonates 58-55 Sum of the oxygen in the bases 8-95
The numbers 9*01 and 8*95 resemble each other
as nearly as could be expected even in analyses
* 100 parts of this wood gave 1-187 ashes,
t 100 parts of this wood gave 1-128 ashes.
CONSTITUENTS OF PLANTS. 97
made for the very purpose of ascertaining the fact
above demonstrated which the analyst in this case
had not in view.
Let us now compare Berthier's analyses of the
ashes of two fir-trees, one of which grew in Nor-
way, the other in Allevard (de'partement de llsere).
One contained 50, the other 25 per cent, of solu-
ble salts. A greater difference in the proportion
of the alkaline bases could scarcely exist between
two totally different plants, and yet even here,
the quantity of oxygen in the bases of both was
the same.
100 parts of the ashes of firwood from Allevard
contained according to Berthier, (Ann. de Chim. et
de Phys. t. xxxii. p. 248,)
Potash and Soda 16-8 in which 3-42 parts must be oxygen.
Lime . 29'5 „ 8'20 „ „
Magnesia . 3'2 „ 1'20 „ „
49-5 12-82
Only part of the potash and soda in these ashes
was in combination with organic acids, the remain-
der was in the form of sulphates, phosphates, and
chlorides. One hundred parts of the ashes con-
tained 3*1 sulphuric acid, 4*2 phosphoric acid, and
0*3 hydrochloric acid, which, together, neutralise a
quantity of base containing 1.20 oxygen. This
number therefore must be subtracted from 12*82.
The remainder 11*62 indicates the quantity of oxy-
gen in the alkaline bases, combined with organic
acids, in the firwood of Allevard.
H
98 OF THE INORGANIC
The firwood of Norway contained in 100 parts :*
Potash . 14-1 of which 2'4 parts would be oxygen.
Soda . 20-7 „ 5'3
Lime . 12%3 „ 3'45 „
Magnesia . 4-35 ,, 1-69 „ „
51-45 12-84
And if the quantity of oxygen of the bases in com-
bination with sulphuric and phosphoric acid, viz-
1* 3 7) be again subtracted from 12*84, 1T47 parts
remain as the amount of oxygen contained in the
bases, which were in combination with organic
acids.
These remarkable approximations cannot be acci-
dental ; and if further examinations confirm them
in other kinds of plants, no other explanation than
that already given can be adopted.
It is not known in what form silica, manganese,
and oxide of iron, are contained in plants, but we
are certain that potash, soda, and magnesia, can be
extracted from all parts of their structure in the
form of salts of organic acids. The same is the case
with lime, when not present as insoluble oxalate of
lime. It must here be remembered, that in plants
yielding oxalic acid, the acid and potash never exist
in the form of a neutral or quadruple salt, but
* This calculation is exact only in the case where the quantity of
ashes is equal in weight for a given quantity of wood ; the difference
cannot, however, be admitted to be so great as to change sensibly the
above proportions. Berthier has not mentioned the proportion of ashes
contained in the wood.
CONSTITUENTS OF PLANTS. 99
always as a double acid salt, on whatever soil they
may grow. The potash in grapes, also, is more fre-
quently found as an acid salt, viz. cream of tartar,
than in the form of a neutral compound. As these
acids and bases are never absent from plants, and
as even the form in which they present themselves
is not subject to change, it may be affirmed, that
they exercise an important influence on the deve-
lopment of the fruits and seeds, and also on many
other functions of the nature of which we are at
present ignorant.
The quantity of alkaline bases existing in a plant
also depends evidently on this circumstance of their
existing only in the form of acid salts, for the capa-
city of saturation of an acid is constant ; and when
we see oxalate of lime in the lichens occupying the
place of woody fibre, which is absent, we must regard
it as certain, that the soluble organic salts are des-
tined to fulfil equally important, though different
functions, so much so, that we could not conceive
the complete development of a plant without their
presence, that is, without the presence of their
acids, and consequently of their bases.
From these considerations we must perceive that
exact and trustworthy examinations of the ashes of
plants of the same kind growing upon different
soils would be of the greatest importance to vege-
table physiology, and would decide whether the
facts above-mentioned are the results of an un-
changing law for each family of plants, and whether
H 2
100 OF THE INORGANIC
an invariable number can be found to express the
quantity of oxygen which each species of plant con-
tains in the bases united with organic acids. In
all probability, such inquiries will lead to most im-
portant results ; for it is clear, that if the production
of a certain unchanging quantity of an organic
acid is required by the peculiar nature of the organs
of a plant, and is necessary to its existence, then
potash or lime must be taken up by it, in order to
form salts with this acid ; that if these do not
exist in sufficient quantity in the soil, other bases
must supply their place ; and that the progress of a
plant must be wholly arrested when none are
present.
Seeds of the Salsola Kali, when sown in common
garden soil, produce a plant containing both potash
and soda ; while the plants grown from the seeds of
this contain only salts of potash, with mere traces @f
muriate of soda. (Cadet.)
The existence of vegetable alkalies in combina-
tion with organic acids gives great weight to the
opinion, that alkaline bases in general are connected
with the development of plants.
If potatoes are grown where they are not supplied
with earth, the magazine of inorganic bases, (in
cellars for example), a true alkali, called Solanin, of
very poisonous nature, is formed in the sprouts
which extend towards the light, while not the
smallest trace of such a substance can be discovered
in the roots, herbs, blossoms, or fruits of potatoes
CONSTITUENTS OF PLANTS. 101
grown in fields. (Otto). In all the species of the Cin-
chona, kinic acid is found ; but the quantity of qui-
nina, cinchonina and liine which they contain is
most variable. From the fixed bases in the products
of incineration, however, we may estimate pretty
accurately the quantity of the peculiar organic
bases. A maximum of the first corresponds to a
minimum of the latter, as must necessarily be the
case if they mutually replace one another according
to their equivalents. We know that different kinds
of opium contain me conic acid, in combination with
very different quantities of narcotina, morphia, eodeia,
&c.3 the quantity of one of these alkaloids diminish-
ing on the increase of the others. Thus, the smallest
quantity of morphia is accompanied by a maximum
of narcotina. Not a trace of meconic acid* can be
discovered in many kinds of opium, but there is not
on this account an absence of acid, for the meconic
is here replaced by sulphuric acid. Here also we
have an example of what has been before stated, for
in those kinds of opium where both these acids exist,
they are always found to bear a certain relative pro-
portion to one another.
But if it be found, as appears to be the case in
the juice of poppies, that an organic acid may be
replaced by an inorganic, without impeding the
growth of a plant, we must admit the probability
* Robiquet did not obtain a trace of meconate of lime from 300 Ibs.
of opium, whilst in other kinds the quantity was very considerable
Ann. de Chim. liii. p. 425.
102 OF THE INORGANIC
of this substitution taking place in a much higher
degree in the case of the inorganic bases.
When roots find their more appropriate base in
sufficient quantity, they will take up less of another.
These phenomena do not show themselves so
frequently in cultivated plants, because they are
subjected to special external conditions for the
purpose of the production of particular constituents
or particular organs.
When the soil, in which a white hyacinth is
growing in the state of blossom, is sprinkled with
the juice of the Phytolaca decandra, the white blos-
soms assume, in one or two hours, a red colour,
which again disappears after a few days under the
influence of sunshine, and they become white and
colourless as before*. The juice in this case evi-
dently enters into all parts of the plant, without
being at all changed in its chemical nature, or with-
out its presence being ^apparently either necessary
or injurious. But this condition is not permanent,
and when the blossoms have become again colour-
less, none of the colouring matter remains ; and if
it should occur, that any of its elements were
adapted for the purposes of nutrition of the plant,
then these alone would be retained, whilst the rest
would be excreted in an altered form by the roots.
Exactly the same thing must happen when we
sprinkle a plant with a solution of chloride of
* Biot, in the Comptes rendus des Seances de 1' Academic des Sciences,
a Paris, ler Semestre, 1837. p. 12.
CONSTITUENTS OF PLANTS. 103
potassium, nitre, or nitrate of strontia ; they will
enter into the different parts of the plant, just as
the coloured juice mentioned above, and will be
found in its ashes if it should be burnt at this
period. Their presence is merely accidental ; but
no conclusion can be hence deduced against the
necessity of the presence of other bases in plants.
The experiments of Macaire-Princep have shown
that plants made to vegetate with their roots in a
weak solution of acetate of lead, and then in rain-
water, yield to the latter all the salt of lead which
they had previously absorbed. They return, there-
fore, to the soil all matters which are unnecessary
to their existence. Again, when a plant, freely
exposed to the atmosphere, rain, and sunshine, is
sprinkled with a solution of nitrate of abrontian, the
salt is absorbed, but it is again separated by the
roots and removed further from them by every
shower of rain, which moistens the soil, so that at
last not a trace of it is to be found in the plant.
Let us consider the composition of the ashes of
two fir-trees as analysed by an acute and most
accurate chemist. One of these grew in Norway
on a soil, the constituents of which never changed,
but to which soluble salts, and particularly common
salt, were conveyed in great quantity by rain-water.
How did it happen that its ashes contained no
appreciable trace of salt, although we are certain
that its roots must have absorbed it after every
shower ?
We can explain the absence of salt in this case
104 OF THE INORGANIC
by means of the direct and positive observations
referred to, which have shown that plants have the
power of returning to the soil all substances unne-
cessary to their existence ; and the conclusion to
which all the foregoing facts lead us, when their
real value and bearing are apprehended, is that the
alkaline bases existing in the ashes of plants must
be necessary to their growth, since if this were not
the case they would not be retained.
The perfect development of a plant according to
this view is dependent on the presence of alkalies
or alkaline earths ; for when these substances are
totally wanting, its growth will be arrested, and
when they are only deficient, it must be impeded.
In order to apply these remarks, let us compare
two kinds of tree, the wood of which contain un-
equal quantities of alkaline bases, and we shall find
that one of these grows luxuriantly in several soils,
upon which the others are scarcely able to vegetate.
For example, 10,000 parts of oak wood yield 250
parts of ashes, the same quantity of fir-wood only
83, of linden-wood 500, of rye 440, and of the herb
of the potato-plant 1500 parts*.
Firs and pines find a sufficient quantity of alkalies
in granitic and barren sandy soils, in which oaks
will not grow ; and wheat thrives in soils favourable
for the linden-tree, because the bases, which are
necessary to bring it to complete maturity, exist
there in sufficient quantity. The accuracy of these
conclusions, so highly important to agriculture and
* Berthier, Annales de Chimie ct cle Physique, t. xxx. p. 248.
CONSTITUENTS OF PLANTS. 105
to the cultivation of forests, can be proved by the
most evident facts.
All kinds of grasses, the Equisetacece, for example,
contain in the outer parts of their leaves and stalk
a large quantity of silicic acid and potash, in the
form of acid silicate of potash. The proportion of
this salt does not vary perceptibly in the soil of
corn-fields, because it is again conveyed to them
as manure in the form of putrifying straw. But
this is not the case in a meadow, and hence we
never find a luxuriant crop of grass* on sandy and
calcareous soils which contain little potash, evi-
dently because one of the constituents indispensable
to the growth of the plants is wanting. Soils formed
from basalt, grauwacke, and porphyry are, caeteris
paribus, the best for meadow land, on account of
the quantity of potash which enters into their com-
position. The potash abstracted by the plants is re-
stored during the annual irrigation-^. That con-
* It would be of importance to examine what alkalies are contained
in the ashes of the sea-shore plants which grow in the humid hollows
of downs, and especially in those of the millet-grass (Hartig).
If potash is not found in them it must certainly be replaced by soda as
in the salsola, or by lime as in the Plumbacfinece.
f A very high value is attached in Germany to the cultivation of
grass as winter provision for cattle, and the greatest care is used in
order to obtain the greatest possible quantity. In the vicinity of Liegen
(a town in Nassau), from three to five perfect crops are obtained from
one meadow, and this is effected by covering the fields with river- water,
which is conducted over the meadow in spring by numerous small
canals. This is found to be of such advantage, that supposing a meadow
not so treated to yield 1000 Ibs. of hay, then from one thus watered
4'5000 Ibs. are produced. In respect to the cultivation of meadows, the
country around Liegen is considered to be the best in all Germany.
106 OF THE INORGANIC
t
tained in the soil itself is inexhaustible in comparison
with the quantity removed by plants.
But when we increase the crop of grass in a
meadow by means of gypsum, we remove a greater
quantity of potash with the hay than can, under
the same circumstances, be restored. Hence it
happens, that after the lapse of several years, the
crops of grass on the meadows manured with gyp-
sum diminish, owing to the deficiency of potash.
But if the meadow be strewed from time to time
with wood-ashes, even with the lixiviated ashes
which have been used by soap-boilers, (in Germany
much soap is made from the ashes of wood,) then
the grass thrives as luxuriantly as before. The
ashes are only a means of restoring the potash.
A harvest of grain is obtained every thirty or
forty years from the soil of the Luneburg heath,
by strewing it with the ashes of the heath-plants
(Erica vulgar is) which grow on it. These plants
during the long period just mentioned collect the
potash and soda, which are conveyed to them by
rain-water ; and it is by means of these alkalies,
that oats, barley, and rye, to which they are indis-
dispensable, are enabled to grow on this sandy
heath.
The woodcutters in the vicinity of Heidelberg
have the privilege of cultivating the soil for their
own use, after felling the trees used for making tan.
Before sowing the land thus obtained, the branches^
roots and leaves are in every case burned, and
CONSTITUENTS OF PLANTS. 10/
<
the ashes used as a manure, which is found to be
quite indispensable for the growth of the grain.
The soil itself, upon which the oats grow in this
district, consists of sandstone ; and although the
trees find in it a quantity of alkaline earths suffi-
cient for their own sustenance, yet in its ordinary
condition it is incapable of producing grain.
The most decisive proof of the use of strong
manure was obtained at Bingen (a town on the
Rhine), where the produce and development of
vines were highly increased by manuring them
with such substances as shavings of horn, &c.,
but after some years the formation of the wood
and leaves decreased to the great loss of the pos-
sessor, to such a degree, that he has long had
cause to regret his departure from the usual me-
thods. By the manure employed by him, the
vines had been too much hastened in their growth ;
in two or three years they had exhausted the
potash in the formation of their fruit, leaves, and
wood, so that none remained for the future crops,
his manure not having contained any potash.
There are vineyards on the Rhine, the plants
of which are above a hundred years old, and all
of these have been cultivated by manuring them
with cow-dung, a manure containing a large pro-
portion of potash, although very little nitrogen.
All the potash, in fact, which is contained in the
food consumed by a cow is again immediately
discharged in its excrements.
108 OF THE INORGANIC
The experience of a proprietor of land in the
vicinity of Gottingen offers a most remarkable
example of the incapability of a soil to produce
wheat or grasses in general, when it fails in any
one of the materials necessary to their growth.
In order to obtain potash, he planted his whole
land with wormwood, the ashes of which are well
known to contain a large proportion of the car-
bonate of that alkali. The consequence was,, that
he rendered his land quite incapable of bearing
grain for many years, in consequence of having
entirely deprived the soil of its potash.
The leaves and small branches of trees contain
the most potash ; and the quantity of them which
is annually taken from a wood, for the purpose of
being employed as litter*, contain more of that
alkali than all the old wood which is cut down.
The bark and foliage of oaks, for example, contain
from 6 to 9 per cent, of this alkali ; the needles of
firs and pines 8 per cent.
With every 2650 Ibs. of fir-wood, which are
yearly removed from an acre of forest, only from
0*114 to 0*53 Ibs. of alkalies are abstracted from
the soil, calculating the ashes at 0.83 per cent.
* [This refers to a custom some time since very prevalent in Germany,
although now discontinued. The leaves and small twigs of trees were
gleaned from the forests by poor people, for the purpose of being used
as litter for their cattle. The trees, however, were found to suffer so
much in consequence, that a strict prohibition is now placed against
their removal. The cause of the injury was that stated in the text.—
TRANS.]
CONSTITUENTS OF PLANTS. 109
The moss, however, which covers the ground, and
of which the ashes are known to contain so much
alkali, continues uninterrupted in its growth, and
retains that potash on the surface, which would
otherwise so easily penetrate with the rain through
the sandy soil. By its decay, an abundant pro-
vision of alkalies is supplied to the roots of the
trees, and a fresh supply is rendered unnecessary.
The supposition of alkalies, metallic oxides, or in-
organic matter in general, being produced by plants,
is entirely refuted by these well-authenticated facts.
It is thought very remarkable, that those plants
of the grass tribe, the seeds of which furnish food
for man, follow him like the domestic animals.
But saline plants seek the sea-shore or saline
springs, and the Chenopodium the dunghill from
similar causes. Saline plants require common
salt, and the plants, which grow only on dunghills,
need ammonia and nitrates, and they are attracted
whither these can be found, just as the dung-fly
is to animal excrements. So likewise none of
our corn plants can bear perfect seeds, that is,
seeds yielding flour, without a large supply of
phosphate of magnesia and ammonia, substances
which they require for their maturity. And hence,
these plants grow only in a soil where these three
constituents are found combined, and no soil is
richer in them, than those where men and animals
dwell together ; where the urine and excrements
of these are found corn -plants appear, because their
1 10 OF THE INORGANIC
seeds cannot attain maturity unless supplied with
the constituents of those matters.
When we find sea-plants near our salt-works,
several hundred miles distant from the sea, we
know that their seeds have been carried there in a
very natural manner, namely, by wind or birds,
which have spread them over the whole surface of
the earth, although they grow only in those places in
which they find the conditions essential to their life.
Numerous small fish, of not more than two
inches in length ( ' Gasterosteus aculeatus), are found
in the salt-pans of the graduating house at Nidda
(a village in Hesse Darmstadt). No living animal
is found in the salt-pans of Neuheim, situated about
18 miles from Nidda ; but the water there contains
so much carbonic acid and lime, that the walls of
the graduating house are covered with stalactites.
Hence the eggs conveyed to this place by birds do
not find the conditions necessary for their develop-
ment, which they found in the former place *.
* " The itch-insect (Acarus Scabiei) is considered by Burdach as the
production of a morbid condition, so likewise lice in children ; the
original generation of the fresh- water muscle (mytiltu) in fish-ponds, of
sea-plants in the vicinity of salt-works, of nettles and grasses, of fish in
pools of rain, of trout in mountain streams, &c , is according to the
same natural philosopher not impossible." A soil consisting of crum-
bled rocks, decayed vegetables, rain and salt water, &c., is here supposed
to possess the power of generating shell-fish, trout, and saltworts (sali-
cornia). All inquiry is arrested by such opinions, when propagated by
a teacher who enjoys a merited reputation, obtained by knowledge and
hard labour. These subjects, however, have hitherto met with the most
superficial observation, although they well merit strict investigation.
The dark, the secret, the mysterious, the enigmatic, is, in fact, too
CONSTITUENTS OF PLANTS. Ill
How much more wonderful and inexplicable does
it appear, that bodies which remain fixed in the
strong heat of a fire, have under certain conditions
the property of volatilizing and, at ordinary tempera-
tures, of passing into a state, of which we cannot
say whether they have really assumed the form of a
gas or are dissolved in one ! Steam or vapours in
general have a very singular influence in causing
the volatilization of these bodies, that is, of causing
them to assume the gaseous form. A liquid during
evaporation communicates the power of assuming
the same state in a greater or less degree to all sub-
stances dissolved in it, although they do not of
themselves possess that property.
Boracic acid is a substance which is completely
fixed in the fire ; it suffers no change of weight
appreciable by the most delicate balance, when ex-
posed to a white heat, and, therefore, it is not vola-
tile. Yet its solution in water cannot be evaporated
by the gentlest heat, without the escape of a sensible
quantity of the acid with the steam. Hence it is
that a loss is always experienced in the analysis of
minerals containing this acid, when liquids in which
it is dissolved are evaporated. The quantity of
boracic acid which escapes with a cubic foot of
steam, at the temperature of boiling water, cannot
seducing for the youthful and philosophic mind, which would penetrate
the deepest depths of nature, without the assistance of the shaft or
ladder of the miner. This is poetry, but not sober philosophical
inquiry.
112 OF THE INORGANIC
be detected by our most sensible re-agents ; and
nevertheless the many hundred tons annually
brought from Italy as an article of commerce, are
procured by the uninterrupted accumulation of
this apparently inappreciable quantity. The hot
steam which issues from the interior of the earth is
allowed to pass through cold water in the lagoons of
Castel Nuova and Cherchiago ; in this way is the
boracic acid gradually accumulated, till at last it
may be obtained in crystals by the evaporation
of the water. It is evident, from the temperature
of the steam, that it must have come out of depths
in which human beings and animals never could
have lived, and yet it is very remarkable and highly
important that ammonia is never absent from it. In
the large works in Liverpool, where natural boracic
acid is converted into borax, many hundred pounds
of sulphate of ammonia are obtained at the same
time.
This ammonia has not been produced by the
animal organism, it existed before the creation of
human beings; it is a part, a primary constituent, of
the globe itself.
The experiments instituted under Lavoisier's
guidance by the Direction des poudres et salpetres,
have proved that during the evaporation of the
saltpetre ley, the salt volatilizes with the water, and
causes a loss which could not before be explained.
It is known also, that in sea storms, leaves of plants
in the direction of the wind are covered with
CONSTITUENTS OF PLANTS. 113
crystals of salt, even at the distance of from 20 to
30 miles from the sea. But it does not require a
storm to cause the volatilization of the salt, for the
air hanging over the sea always contains enough of
this substance to make a solution of nitrate of
silver turbid, and every breeze must carry this
away. Now, as thousands of tons of sea-water
annually evaporate into the atmosphere, a corre-
sponding quantity of the salts dissolved in it, viz.
of common salt, chloride of potassium, magnesia,
and the remaining constituents of the sea-water will
be conveyed by wind to the land.
This volatilization is a source of considerable loss
in salt-works, especially where the proportion of
salt in the water is not large. This has been com-
pletely proved at the salt-works of Nauheim, by
the very intelligent director of that establishment,
M. WUhelmi. He hung a plate of glass between two
evaporating houses, which were about 1200 paces
distant from each other, and found in the morning,
after the drying of the dew, that the glass was
covered with crystals of salt on one or the other
side, according to the direction of the wind.
By the continual evaporation of the sea, its salts*
* According to Mareet, sea-water contains in 1000 parts,
26'660 Chloride of Sodium.
4-660 Sulphate of Soda.
1 -232 Chloride of Potassium.
5-152 Chloride of Magnesium.
1-5 Sulphate of Lime.
J
114 OF THE INORGANIC
are spread over the whole surface of the earth ; and
being subsequently carried down by the rain, fur-
nish to the vegetation those salts necessary to its ex-
istence. This is the origin of the salts found in the
ashes of plants, in those cases where the soil could
not have yielded them .
In a comprehensive view of the phenomena of
nature, we have no scale for that which we
are accustomed to name, small or great ; all our
ideas are proportioned to what' we see around us,
but how insignificant are they in comparison with
the whole mass of the globe ! that which is scarcely
observable in a confined district appears incon-
ceivably large when regarded in its extension
through unlimited space. The atmosphere contains
only a thousandth part of its weight of carbonic
acid ; and yet small as this proportion appears, it
is quite sufficient to supply the whole of the present
generation of living beings with carbon for a thou-
sand years, even if it were not renewed. Sea- water
contains TT^OO" °f its weight of carbonate of lime ;
and this quantity, although scarcely appreciable
in a pound, is the source from which myriads of
marine mollusca and corals are supplied with mate-
rials for their habitations.
Whilst the air contains only from 4 to 6 ten -thou-
sandth parts of its volume of carbonic acid, sea-
water contains 100 times more, (10,000 volumes of
sea-water contain 620 volumes of carbonic acid —
CONSTITUENTS OF PLANTS. 115
Laurent, Bouillon, Lagrange). Ammonia* is also
found in this water, so that the same conditions
which sustain living beings on the land are com-
bined in this medium, in which a whole world of
other plants and animals exist.
The roots of plants are constantly engaged in
collecting from the rain those alkalies which formed
part of the sea- water, and also those of the water of
springs, which penetrates the soil. Without alka-
lies and alkaline bases most plants could not exist,
and without plants the alkalies would disappear
gradually from the surface of the earth.
When it is considered, that sea-water contains
less than one-millionth of its own weight of iodine,
and that all combinations of iodine with the metallic
bases of alkalies are highly soluble in water, some
provision must necessarily be supposed to exist in
the organization of sea- weed and the different kinds
of Fuci, by which they are enabled during their life
to extract iodine in the form of a soluble salt from
sea-water, and to assimilate it in such a manner,
that it is not again restored to the surrounding
medium. These plants are collectors of iodine,
just as land-plants are of alkalies ; and they yield
us this element, in quantities such as we could not
otherwise obtain from the water without the evapo-
ration of whole seas.
* When the solid saline residue obtained by the evaporation of sea-
water is heated in a retort to redness, a sublimate of sal-ammoniac is
obtained. — MARCET.
I 2
116 THE ART OF CULTURE.
We take it for granted, that the sea plants
require metallic iodides for their growth, and that
their existence is dependent on the presence of
those substances. With equal justice, then, we
conclude, that the alkalies and alkaline earths,
always found in the ashes of land-plants, are like-
wise necessary for their development.
THE ART OF CULTURE.
THE conditions necessary for the life of all vege-
tables have been considered in the preceding part
of the work. Carbonic acid, ammonia, and water
yield elements for all the organs of plants. Certain
inorganic substances — salts and metallic oxides —
serve peculiar functions in their organism, and
many of them must be viewed as essential consti-
tuents of particular parts.
The atmosphere and the soil offer the same kind
of nourishment to the leaves and roots. The
former contains a comparatively inexhaustible sup-
ply of carbonic acid and ammonia ; the latter, by
means of its humus, generates constantly fresh
carbonic acid, whilst, during the winter, rain and
snow introduce into the soil a quantity of am-
monia, sufficient for the development of the leaves
and blossoms.
The complete, or it may be said, the absolute
insolubility in cold water of vegetable matter in
progress of decay, .(humus,) appears on closer con-
sideration to be a most wise arrangement of na-
USE OF THE HUMUS. 1 \7
ture. For if humus possessed even a smaller de-
gree of solubility, than that ascribed to the sub-
stance called humic acid, it must be dissolved by
rain-water. Thus, the yearly irrigation of mea-
dows (see note at page 105), which lasts for several
weeks, would remove a great part of it from the
ground, and a heavy and continued rain would
impoverish a soil. But it is soluble only when
combined with oxygen ; it can be taken up by
water, therefore, only as carbonic acid.
When kept in a dry place, humus may be pre-
served for centuries, but when moistened with
water, it converts the surrounding oxygen into
carbonic acid. As soon as the action of the air
ceases, that is, as soon as it is deprived of oxygen,
the humus suffers no further change. Its decay
proceeds only when plants grow in the soil con-
taining it ; for they absorb by their roots the car-
bonic acid as it is formed. The soil receives again
from living plants the carbonaceous matter it thus
loses, so that the proportion of humus in it does
not decrease.
The stalactitic caverns in Franconia, and those in
the vicinity of Baireuth, and Streitberg, lie beneath
a fertile arable soil ; the abundant decaying vege-
tables or humus in this soil, being acted on by
moisture and air, constantly evolve carbonic acid,
which is dissolved by the rain. The rain-water
thus impregnated permeates the porous limestone,
which forms the walls and roofs of the caverns, and
118 THE ART OF CULTURE.
dissolves in its passage as much carbonate of lime
as corresponds to the quantity of carbonic acid
contained in it. Water and the excess of carbonic
acid evaporate from this solution when it has
reached the interior of the caverns, and the lime-
stone is deposited on the walls and roofs in crystal-
line crusts of various forms. There are few spots
on the earth where so many circumstances favour-
able to the production of humate of lime are com-
bined, if the humus actually existed in the soil in
the form of humic acid. Decaying vegetable
matter, water, and lime in solution, are brought
together, but the stalactites formed contain no
trace, of vegetable matter, and no humic acid ; they
are of a glistening white or yellowish colour, and
in part transparent, like calcareous spar, and may
be heated to redness without becoming black.
The subterranean vaults in the old castles near
the Rhine, the " Bergstrasse " and Wetherau, are
constructed of sandstone, granite, or basalt, and
present appearances similar to the limestone ca-
verns. The roofs of these vaults or cellars are
covered externally to the thickness of several feet
with vegetable mould, which has been formed by
the decay of plants. The rain falling upon them
sinks through the earth, and dissolves the mortar
by means of the carbonic acid derived from the
mould ; and this solution evaporating in the inte-
rior of the vaults, covers them with small thin sta-
lactites, which are quite free from humic acid.
USE OF THE HUMUS. 1 19
In such a filtering apparatus, built by the hand
of nature, we have placed before us experiments
which have been continued for a hundred or a
thousand years. Now, if water possessed the
power of dissolving a hundred-thousandth part
of its own weight of humic acid or humate of lime,
and humic acid were present, we should find the
inner surface of the roofs of these vaults and ca-
verns covered with these substances ; but we can-
not detect the smallest trace of them. There
could scarcely be found a more clear and con-
vincing proof of the absence of the humic acid of
chemists in common vegetable mould.
The common view, which has been adopted
respecting the modus operandi of humic acid, has
given occasion to the following inexplicable phe-
nomenon : — A very small quantity of humic acid
dissolved in water gives it a yellow or brown co-
lour. Hence it would be supposed, that a soil
would be more fruitful in proportion as it was
capable of giving this colour to water, that is, of
yielding it humic acid. But it is very remarkable
that plants do not thrive in such a soil, and that
all manure must have lost this property before it
can exercise a favourable influence upon their
vegetation. Water from barren peat soils and
marshy meadows, upon which few plants flourish,
contains much of this humic acid ; but all agricul-
turists and gardeners agree that the most suitable
and best manure for plants is that which has
120 THE ART OF CULTURE.
completely lost the property of giving a colour to
water.
The soluble substance, which gives to water a
brown colour, is a product of the putrefaction of
all animal and vegetable matters ; its formation is
an evidence, that there is not oxygen sufficient
to begin or at least to complete the decay. The
brown solutions, containing this substance, are
decolourized in the air, by absorbing oxygen, and
a black coaly matter precipitates — the substance
named " coal of humus." Now if a soil were im-
pregnated with this matter, the effect on the roots
of plants would be the same as that of entirely de-
priving the soil of oxygen ; plants would as little
be able to grow in such ground, as they would if
hydrated protoxide of iron were mixed with the
soil. All plants die in soils and water which con-
tain no oxygen ; absence of air acts exactly in the
same manner as an excess of carbonic acid. Stag-
nant water 'on a marshy soil excludes air, but a
renewal of water has the same effect as a renewal
of air, because water contains it in solution. If
the water is withdrawn from a marsh, free access
is given to the air, and the marsh is changed into
a fruitful meadow.
In a soil to which the air has no access, or at
most but very little, the remains of animals and
vegetables do not decay, for they can only do so
when freely supplied with oxygen ; but they undergo
putrefaction, for which air is present in sufficient
USE OF THE HUMUS. 121
quantity. Putrefaction is known to be a most
powerful deoxidising process, the influence of
which extends to all surrounding bodies, even
to the roots and the plants themselves. All sub-
stances from which oxygen can be extracted yield
it to putrefying bodies ; yellow oxide of iron passes
into the state of black oxide, sulphate of iron into
sulphuret of iron, &c.
The frequent renewal of air by ploughing, and
the preparation of the soil, especially its contact
with alkaline metallic oxides, the ashes of brown
coal, burnt lime or limestone, change the putre-
faction of its organic constituents into a pure pro-
cess of oxidation ; and from the moment- at which
all the organic matter existing in a soil enters
into a state of oxidation or decay, its fertility is /
-'increased. The oxygen is no longer employed for
the conversion of the brown soluble matter into
the insoluble coal of humus, but serves for the
formation of carbonic acid. This change takes
place very slowly, and, in some instances, the
oxygen is completely excluded by it. And, when-
ever this happens, the soil loses its fertility. Thus,
in the vicinity of Salzhausen (a village in Hesse
Darmstadt, famed for its mineral springs), upon
a meadow called Grimschwalheimer, unfruitful
spots are seen here and there covered with a
yellow grass. If a hole be bored from 20 to 25
feet deep in one of these spots, carbonic acid is
emitted from it with such violence, that the noise
122 THE ART OF CULTURE.
made by the escape of the gas may be distinctly
heard at the distance of several feet. Here the
carbonic acid rising to the surface displaces com-
pletely all the air, and consequently all the oxygen,
from the soil ; and without oxygen, neither seeds
nor roots can be developed ; a plant will not vege-
tate in pure nitrogen or carbonic acid gas.
Humus supplies young plants with nourishment
by the roots, until their leaves are matured suffi-
ciently to act as exterior organs of nutrition ; its
quantity heightens the fertility of a soil by yielding
more nourishment in this first period of growth,
and consequently by increasing the number of
organs of atmospheric nutrition. Those plants,
which receive their first food from the substance
of their seeds, such as bulbous plants, could com-
pletely dispense with humus ; its presence is use-
ful only in so far as it increases and accelerates
their development, but it is not necessary, — indeed,
an excess of it at the commencement of their
growth is, in a certain measure, injurious.
The amount of food which young plants can
take from the atmosphere in the form of carbonic
acid and ammonia is limited ; they cannot assimi-
late more than the air contains. Now, if the
quantity of their stems, leaves, and branches
has been increased by the excess of food yielded
by the soil at the commencement of their deve-
lopment, they will require for the completion of
their growth, and for the formation of their bios-
NUTRITION AND GROWTH OF PLANTS.
soms and fruits, more nourishment from the air
than it can afford, and consequently they will not
reach maturity. In many cases the nourishment
afforded by the air under these circumstances suf-
fices only to complete the formation of the leaves,
stems, and branches. The same result then ensues
as when ornamental plants are transplanted from
the pots in which they have grown to larger ones,
in which their roots are permitted to increase and
multiply. All their nourishment is employed for
the increase of their roots and leaves ; they spring,
as it is said, into an herb or weed, but do not
blossom. When, on the contrary, we take away
part of the branches, and of course their leaves
with them, from dwarf trees, since we thus prevent
the development of new branches, an excess of
nutriment is artificially procured for the trees, and
is employed by them in the increase of the blossoms
and enlargement of the fruit. It is to effect this
purpose that vines are pruned.
A new and peculiar process of vegetation ensues
in all perennial plants, such as shrubs, fruit and
forest trees, after the complete maturity of their
fruit. The stem of annual plants, at this period
of their growth, becomes woody, and their leaves
change in colour. The leaves of trees and shrubs
on the contrary remain in activity until the com-
mencement of the winter. The formation of the
layers of wood progresses, the wood becomes harder
and more solid, but after August the leaves form no
124 THE ART OF CULTURE.
more wood : all the carbonic acid which the plants
now absorb is employed for the production of nutri-
tive matter for the following year : instead of woody
fibre, starch is formed, and is diffused through
every part of the plant by the autumnal sap
(seve d'Aout) *. According to the observations of
M. Heyer, the starch thus deposited in the body of
the tree can be recognised in its known form by
the aid of a good microscope. The barks of
several aspens and pine trees-}- 'contain so much of
this substance that it can be extracted from them
as from potatoes, by trituration with water. It
exists also in the roots and other parts of perennial
plants. A very early winter or sudden change of
temperature prevents the formation of this provi-
sion for the following year ; the wood, as in the
case of the vine-stock, for example, does not ripen,
and its growth is in the next year very limited.
From the starch thus accumulated, sugar and
gum are produced in the succeeding spring, while
from the gum those constituents of the leaves and
young sprouts which contain no nitrogen are, in
their turn, formed. After potatoes have germi-
nated, the quantity of starch in them is found
diminished. The juice of the maple tree ceases to
be sweet from the loss of its sugar when its buds,
blossoms, and leaves attain their maturity.
* Hartig, in Erdmann and Schweigger-S'eidels Journal, V. 217. 1835.
t It is well known that bread is made from the barks of pines in
Sweden during famines.
NUTRITION AND GROWTH OF PLANTS. 125
The branch of a willow, which contains a large
quantity of granules of starch in every part of its
woody substance, puts forth both roots and leaves
in pure distilled rain-water ; but in proportion
as it grows, the starch disappears, it being evidently
exhausted for the formation of the roots and leaves.
In the course of these experiments, M. Heyer made
the interesting observation, that such branches
when placed in snow-water (which contains ammo-
nia) produced roots three or four times longer than
those which they formed in pure distilled water,
and that this pure water remained clear, while the
rain-water gradually acquired a yellow colour.
Upon the blossoming of the sugar-cane, like-
wise, part of the sugar disappears ; and it has been
ascertained, that the sugar does not accumulate in
the beet-root until after the leaves are completely
formed.
Much attention has recently been drawn to the
fact that the produce of potatoes may be much
increased by plucking off the blossoms from the
plants producing them, a result quite consistent
with theory. This important observation has been
completely confirmed by M. Zeller, the director of
the Agricultural Society at Darmstadt. In the year
1839 two fields of the same size, lying side by side
and manured in the same manner, were planted
with potatoes. When the plants had flowered, the
blossoms were removed from those in one field,
while those in the other field were left untouched.
126 THE ART OF CULTURE.
The former produced 47 /^ •--, the latter only
Q^7 // (J £ &v '
67 «fy.
These well-authenticated observations remove
every doubt as to the part which sugar, starch, and
gum play in the development of plants ; and it ceases
to be enigmatical, why these three substances exer-
cise no influence on the growth or process of nutri-
tion of a matured plant, when supplied to them as
food.
The accumulation of starch in plants during the
autumn has been compared, although certainly
erroneously, to the fattening of hibernating animals
before their winter sleep ; but in these animals
every vital function, except the process of respira-
tion is suspended, and they only require, like a
lamp slowly burning, a substance rich in carbon
and hydrogen to support the process of combustion
in the lungs. On their awakening from their
torpor in the spring, the fat has disappeared, but
has not served as nourishment. It has not caused
the least increase in any part of their body, neither
has it changed the quality of any of their organs.
With nutrition, properly so called, the fat in these
animals has not the least connexion.
The annual plants form and collect their future
nourishment in the same way as the perennial ;
they store it in their seeds in the form of vegetable
albumen, starch, and gum, which are used by the
germs for the formation of their leaves and first
radicle fibres. The proper nutrition of the plants,
NUTRITION AND GROWTH OF PLANTS. 127
their increase in size, begins after these organs are
formed.
Every germ and every bud of a perennial plant
is the engrafted embryo of a new individual, while
the nutriment accumulated in the stem and roots,
corresponds to the albumen of the seeds.
Nutritive matters are, correctly speaking, those
substances which, when presented from without,
are capable of sustaining the life and all the func-
tions of an organism, by furnishing to the different
parts of plants the materials for the production of
their peculiar constituents.
In animals, the blood is the source of the mate-
rial of the muscles and nerves ; by one of its com-
ponent parts, the blood supports the process of
respiration, by others, the peculiar vital functions ;
every part of the body is supplied with nourish-
ment by it, but its own production is a special
function, without which we could not conceive life
to continue. If we destroy the activity of the
organs which produce it, or if we inject the blood of
one animal into the veins of another, at all events,
if we carry this beyond certain limits, death is the
consequence.
If we could introduce into a tree woody fibre in
state of solution, it would be the same thing as
placing a potato plant to vegetate in a paste of
starch. The office of the leaves is to form starch,
woody fibre, and sugar ; consequently, if we con-
128 THE ART OP CULTURE.
vey these substances through the roots, the vital
functions of the leaves must cease, and if the pro-
cess of assimilation cannot take another form,
the plant must die.
Other substances must be present in a plant, be-
sides the starch, sugar, and gum, if these are to take
part in the development of the germ, leaves, and first
radicle fibres. There is no doubt that a grain of
wheat contains within itself the component parts
of the germ and of the radi'cle fibres, and we
must suppose, exactly in the proportion necessary
for their formation. These component parts are
starch and gluten ; and it is evident that neither
of them alone, but that both simultaneously
assist in the formation of the root, for they both
suffer changes under the action of air, moisture,
and a suitable temperature. The starch is con-
verted into sugar, and the gluten also assumes a
new form, and both acquire the capability of being
dissolved in water, and of thus being conveyed
to every part of the plant. Both the starch and the
gum are completely consumed in the formation
of the first part of the roots and leaves ; an excess
of either could not be used in the formation of
leaves, or in any other way.
The conversion of starch into sugar during the
germination of grain is ascribed to a vegetable
principle called diastase, which is generated during
the act of commencing germination. But this
NUTRITION AND GROWTH OF PLANTS. 129
mode of transformation can also be effected by
gluten, although it requires a longer time. Seeds,
which have germinated, always contain much more
diastase than is necessary for the conversion of
their starch into sugar, for five parts by weight of
starch can be converted into sugar by one part of
malted barley. This excess of diastase can by no
means be regarded as accidental, for, like the starch,
it aids in the formation of the first organs of the
young plant, and disappears with the sugar ; dia-
stase contains nitrogen and furnishes the elements
of vegetable albumen.
Carbonic acid, water, and ammonia, are the food
of fully- developed plants ; starch, sugar, and gum,
serve, when accompanied by an azotised substance,
to sustain the embryo, until its first organs of nu-
trition are unfolded. The nutrition of a foetus and
development of an egg proceed in a totally different
manner from that of an animal which is separated
from its parent ; the exclusion of air does not en^
danger the life of the foetus, but would certainly
cause the death of the independent animal. In the
same manner, pure water is more advantageous to
the growth of a young plant, than that containing car-
bonic acid, but after a month the reverse is the case.
The formation of sugar in maple-trees does not
take place in the roots, but in the woody substance
of the stem. The quantity of sugar in the sap
augments until it reaches a certain height in the
K
130 THE ART OF CULTURE.
stem of the plant, above which point it remains
stationary.
Just as germinating barley produces a substance
which, in contact with starch, causes it to lose its
insolubility and to become sugar, so in the roots of
the maple, at the commencement of vegetation, a
substance must be formed, which, being dissolved
in water, permeates the wood of the trunk, and
converts into sugar the starch, or whatever it may
be, which it finds deposited there. It is certain,
that when a hole is bored into the trunk of a maple-
tree just above its roots, filled with sugar, and then
closed again, the sugar is dissolved by the ascend-
ing sap. It is further possible, that this sugar may
be disposed of in the same manner as that formed
in the trunks ; at all events it is certain, that the
introduction of it does not prevent the action of
the juice upon the starch, and since the quantity
of sugar present is now greater than can be ex-
hausted by the leaves and buds, it is excreted from
the surface of the leaves or bark. Certain diseases
of trees, for example that called honey-dew, evi-
dently depend on the want of the due proportion
between the quantity of the azotised and that of
the unazotised substances which are supplied to
them as nutriment.
In whatever form, therefore, we supply plants
with those substances which are the products of
their own action, in no instance do they appear to
NECESSITY OF NITROGENOUS SUBSTANCES.
have any effect upon their growth, or to replace
what they have lost. Sugar, gum, and starch, are
not food for plants, and the same must be said of
humic acid, which is so closely allied to them in
composition.
If now we direct our attention to the particular
organs of a plant, we find every fibre and every
particle of wood surrounded by a juice containing
an azotised matter ; while the starch granules and
sugar are enclosed in cells formed of a substance
containing nitrogen. Indeed everywhere, in all
the juices of the fruits and blossoms, we find a
substance, destitute of nitrogen, accompanied by
one which contains that element.
The wood of the stem cannot be formed, quasi
wood, in the leaves, but another substance must
be produced, which is capable of being transformed
into wood. This substance must be in a state of
solution, and accompanied by a compound contain-
ing nitrogen ; it is very probable, that the wood
and the vegetable gluten, the starch granules and
the cells containing them, are formed simultane-
ously, and in this case, a certain fixed proportion
between them would be a condition necessary for
their production.
According to this view the assimilation of the
substances generated in the leaves will (cceteris
paribus) depend on the quantity of nitrogen con-
tained in the food. When a sufficient quantity of
nitrogen is not present to aid in the assimilation of
K 2
132 THE ART OF CULTURE.
the substances which do not contain it, these sub-
stances will be separated as excrements from the
bark, roots, leaves, and branches. The exudations
of mannite, gum, and sugar, in strong and healthy
plants cannot be ascribed to any other cause *.
Analogous phenomena are presented by the
process of digestion in the human organism. In
order that the loss which every part of the body
sustains by the processes of respiration and perspira-
tion may be restored to it, the 'organs of digestion
require to be supplied with food, consisting of sub-
stance containing nitrogen, and of others destitute
of it, in definite proportions. If the substances
which do not contain nitrogen preponderate, either
they will be expended in the formation of fat, or
they will pass unchanged through the organism.
This is particularly observed in those people who live
almost exclusively upon potatoes ; their excrements
contain a large quantity of unchanged granules of
starch, of which no trace can be detected when
gluten, or flesh, is taken in proper proportions,
because, in this case, the starch has been rendered
capable of assimilation. Potatoes which, when
mixed with hay alone, are scarcely capable of sup-
porting the strength of a horse, form with bread
and oats a strong and wholesome fodder.
* M. Trapp in Giessen possesses a Clerodendron fragram, which
grows in the house, and exudes on the surface of its leaves in September
large colourless drops of sugar-candy, which form regular crystals upon
drying; I am not aware whether the juice of this plant contains sugar.
INFLUENCE OF THE FOOD ON THE PRODUCE. 133
It will be evident from the preceding considera-
tions, that the products generated by a plant may
vary exceedingly, according to the substances given
it as food. A superabundance of carbon in the
state of carbonic acid conveyed through the roots
of plants, without being accompanied by nitrogen,
cannot be converted either into gluten, albumen,
wood, or any other component part of an organ ;
but either it will be separated in the form of excre-
ments, such as sugar, starch, oil, wax, resin, man-
nite or gum, or these substances will be deposited
in greater or less quantity in the wide cells and
vessels.
The quantity of gluten, vegetable albumen, and
mucilage, will augment when plants are supplied
with an excess of food containing nitrogen ; and
ammoniacal salts will remain in the sap, when, for
example, in the culture of the beet, we manure the
soil with a highly nitrogenous substance, or when
we suppress the functions of the leaves, by removing
them from the plant.
We know that the ananas is scarcely eatable
in its wild state, and that it shoots forth a great
quantity of leaves, when treated with rich animal
manure, without the fruit on that account acquiring
a large amount of sugar ; that the quantity of starch
in potatoes increases, when the soil contains much
humus, but decreases when the soil is manured
with strong animal manure, although then the
number of cells increases, the potatoes acquiring
134 THE ART OF CULTURE.
in the first case a mealy, in the second a soapy, con-
sistence. Beet-roots taken from a barren sandy soil
contain a maximum of sugar, and no ammoniacal
salts; and the Teltowa turnip loses its mealy state in
a manured land, because there, all the circumstances
necessary for the formation of cells are united.
An abnormal production of certain component
parts of plants presupposes a power and capability
of assimilation, to which the most powerful chemi-
cal action cannot be compared. The best idea of
it may be formed, by considering that it surpasses
in power the strongest galvanic battery, with which
we are not able to separate the oxygen from car-
bonic acid. The affinity of chlorine for hydrogen,
and its power to decompose water under the influ-
ence of light, and set at liberty its oxygen, cannot be
considered as at all equalling the power and energy
with which a leaf separated from a plant decom-
poses the carbonic acid which it absorbs.
The common opinion that only the direct solar
rays can effect the decomposition of carbonic acid
in the leaves of plants, and that reflected or diffused
light does not possess this property, is wholly an
error, for exactly the same constituents are gene-
rated in a number of plants, whether the direct
rays of the sun fall upon them, or whether they
grow in the shade. They require light, and,
indeed, sun-light, but it is not necessary that the
direct rays of the sun reach them. Their functions
certainly proceed with greater intensity and rapidity
INFLUENCE OF LIGHT. 135
in sunshine, than in the diffused light of day ; but
there is nothing more in this than the similar
action which light exercises on ordinary chemical
combinations, it merely accelerates in a greater or
less degree the action already subsisting.
Chlorine and hydrogen combining form muriatic
acid. This combination is effected in a few hours
in common daylight, but it ensues instantly with a
violent explosion, under exposure to the direct
solar rays, whilst not the slightest change in the
two gases takes place in perfect darkness. When
the liquid hydrocarburet of chlorine, resulting
from the union of the olefiant gas of the Dutch
chemists with chlorine, is exposed in a vess'el with
chlorine gas to the direct solar rays, chloride of
carbon is immediately produced ; but the same
compound can be obtained with equal facility in
the diffused light of day, a longer time only being
required. When this experiment is performed in
the way first mentioned, two products only are
observed (muriatic acid and per chloride of carbon);
whilst by the latter method, a class of intermediate
bodies are produced, in which the quantity of
chlorine constantly augments, until at last the
whole liquid hydrocarburet of chlorine is converted
into the same two products as in the first case.
Here,, also, not the slightest trace of decomposition
takes place in the dark. Nitric acid is decomposed
in common daylight into oxygen, and peroxide of
nitrogen and chloride of silver becomes black in
136 THE ART OF CULTURE.
the diffused light of day, as well as in the direct
solar rays ; — in short, all actions of a similar kind
proceed in the same way in diffused light as well
as in the solar light, the only difference consisting
in the time in which they are effected. It cannot
be otherwise in plants, for the mode of their nutri-
ment is the same in all, and their component
substances afford proof, that their food has suffered
absolutely the same change, whether they grow in
the sunshine or in the shade.
All the carbonic acid therefore which we supply
to a plant will undergo a transformation, provided
its quantity be not greater than can be decomposed
by the leaves. We know that an excess of carbonic
acid kills plants, but we know also that nitrogen,
to a certain degree, is not essential for the decom-
position of carbonic acid. All the experiments
hitherto instituted, prove that fresh leaves placed in
water, impregnated with carbonic acid, and exposed
to the influence of solar light, emit oxygen gas,
whilst the carbonic acid disappears. Now, in these
experiments no nitrogen is supplied at the same
time with the carbonic acid ; hence no other con-
clusion can be drawn from them, than that nitrogen
is not necessary for the decomposition of carbonic
acid, — for the exercise, therefore, of one of the
functions of plants. And yet the presence of a
substance containing this element appears to be
indispensable for the assimilation of the products
newly formed by the decomposition of the carbonic
INFLUENCE OF THE FOOD ON THE PRODUCE. 137
acid; and their consequent adaptation for entering
into the composition of the diiferent organs.
The carbon abstracted from the carbonic acid
acquires in the leaves a new form, in which it is
soluble and transferable to all parts of the plant.
In this new form the carbon aids in constituting
several new products ; these are named sugar when
they possess a sweet taste, gum or mucilage when
tasteless, and excrementitious matters when ex-
pelled by the roots.
Hence it is evident, that the quantity and quality
of the substances generated by the vital processes
of a plant will vary according to the proportion
of the diiferent kinds of food with which it is
supplied. The development of every part of a
plant in a free and uncultivated state depends on
the amount and nature of the food aiforded to it, by
the spot on which it grows. A plant is developed
on the most sterile and unfruitful soil, as well as on
the most luxuriant and fertile, the only difference
which can be observed being in its height and size,
in the number of its twigs, branches, leaves, blos-
soms, and fruit. Whilst the individual organs of a
plant increase on a fertile soil, they diminish on
another, where those substances which are neces-
sary for their formation are not so bountifully
supplied ; and the proportion of the constituents,
which contain nitrogen, and of those which do not,
in plants varies with the amount of nitrogenous
matters in their food.
138 THE ART OF CULTURE.
The development of the stem,, leaves, blossoms,,
and fruit of plants is dependent on certain condi-
tions,, the knowledge of which enables us to exer-
cise some influence on their internal constituents as
well as on their size. It is the duty of the natural
philosopher to discover what these conditions are; for
the fundamental principles of agriculture must be
based on a knowledge of them. There is no pro-
fession which can be compared in importance with
that of agriculture, for to it belongs the production
of food for man and animals ; on it depends the wel-
fare and development of the whole human species.,
the riches of states, and all commerce. There is no
other profession in which the application of correct
principle is productive of more beneficial effects,
or is of greater and more decided influence. Hence
it appears quite unaccountable, that we may vainly
search for one leading principle in the writings of
agriculturists and vegetable physiologists.
The methods employed in the cultivation of land
are different in every country, and in every district ;
and when we inquire the causes of these differences
we receive the answer, that they depend upon cir-
cumstances. (Les circonstances font les assolemens.)
No answer could show ignorance more plainly,
since no one has ever yet devoted himself to ascer-
tain what these circumstances are. Thus also when
we inquire in what manner manure acts, we are
answered by the most intelligent men, that its
action is covered by the veil of Isis ; and when we
MANURE. 139
demand further what this means, we discover merely
that the excrements of men and animals are sup-
posed to contain an incomprehensible something
which assists in the nutrition of plants, and
increases their size. This opinion is embraced
without even an attempt being made to discover
the component parts of manure, or to become
acquainted with its nature.
In addition to the general conditions, such as
heat, light, moisture, and the component parts of
the atmosphere, which are necessary for the growth
of all plants, certain substances are found to exer-
cise a peculiar influence on the development of
particular families. These substances either are
already contained in the soil, or are supplied to it
in the form of the matters known under the general
name of manure. But what does the soil contain,
and what are the components of the substances
used as manure ? Until these points are satisfac-
torily determined, a rational system of agriculture
cannot exist. The power and knowledge of the phy-
siologist of the agriculturist and chemist must be
united for the complete solution of these questions ;
and in order to attain this end, a commencement
must be made.
The general object of agriculture is to pro-
duce in the most advantageous manner certain
qualities, or a maximum size, in certain parts or
organs of particular plants. Now, this object can
be attained only by the application of those sub-
HO THE ART OF CULTURE.
stances which we know to be indispensable to the
development of these parts or organs,, or by
supplying the conditions necessary to the produc-
Jfon of the qualities desired.
The rules of a rational system of agriculture
should enable us, therefore, to give to each plant
that which it requires for the attainment of the
object in view.
The special object of agriculture is to obtain an
abnormal development and production of certain
parts of plants, or of certain vegetable matters,
which are employed as food for man and animals,
or for the purposes of industry.
The means employed for effecting these two
purposes are very different. Thus the mode of
culture, employed for the purpose of procuring fine
pliable straw for Florentine hats, is the very oppo-
site to that which must be adopted in order to
produce a maximum of corn from the same plant.
Peculiar methods must be used for the production
of nitrogen in the seeds, others for giving strength
and solidity to the straw, and others again must be
followed when we wish to give such strength and
solidity to the straw as will enable it to bear the
weight of the ears.
We must proceed in the culture of plants in pre-
cisely the same manner as we do in the fattening
of animals. The flesh of the stag and roe, or of
wild animals in general, is quite devoid of fat, like
the muscular flesh of the Arab ; or it contains only
COMPOSITION OF FERTILE SOILS. 141
small quantities of it. The production of flesh and
fat may be artificially increased; all domestic
animals, for example, contain much fat. We give
food to animals, which increases the activity of
certain organs, and is itself capable of being trans-
formed into fat. We add to the quantity of food, or
we lessen the processes of respiration and perspira-
tion by preventing motion. The conditions neces-
sary to effect this purpose in birds are different
from those in quadrupeds ; and it is well known
that charcoal powder produces such an excessive
growth of the liver of a goose, as at length causes
the death of the animal.
The increase or diminution of the vital activity
of vegetables depends only on heat and solar light,
which we have not arbitrarily at our disposal : all
that we can do is to supply those substances which
are adapted for assimilation by the power already
present in the organs of the plant. But what then
are these substances ? They may easily be detected
by the examination of a soil, which is always fer-
tile in given cosmical and atmospheric conditions ;
for it is evident, that the knowledge of its state and
composition must enable us to discover the circum-
stances under which a sterile soil may be rendered
fertile. It is the duty of the chemist to explain
the composition of a fertile soil, but the discovery
of its proper state or condition belongs to the agri-
culturist ; our present business lies only with the
former.
142 THE ART OF CULTURE.
Arable land is originally formed by the crum-
bling of rocks, and its properties depend on the
nature of their principal component parts. Sand,
clay, and lime, are the names given to the
principal constituents of the different kinds of
soil.
Pure sand and pure limestone, in which there
are no other inorganic substances except siliceous
earth, carbonate or silicate of lime, form absolutely
barren soils. But argillaceous earths form always
a part of fertile soils. Now from whence come the
argillaceous earths in arable land; what are their
constituents, and what part do they play in favour-
ing vegetation ? They are produced by the disin-
tegration of aluminous minerals by the action of
the weather ; the common potash and soda fel-
spars, Labrador spar, mica, and the zeolites, are
the most common aluminous earths, which undergo
this change. These minerals are found mixed
with other substances in granite, gneiss, mica-slate,
porphyry, clay-slate, grauwacke, and the volcanic
rocks, basalt, clinkstone, and lava. In the grau-
wacke, we have pure quartz, clay-slate, and lime ;
in the sandstones, quartz and loam. The transition
limestone and the dolomites contain an intermix-
ture of clay, felspar, porphyry, and clay-slate ; and
the mountain limestone is remarkable for the
quantity of argillaceous earths which it contains.
Jura limestone contains 3 — 20, that of the Wur-
temberg Alps 45—50 per cent, of these earths.
COMPOSITION OF SOILS. 143
And in the muschelkalk and the calcaire grassier
they exist in greater or less quantity.
It is known, that the aluminous minerals are the
most widely diffused on the surface of the earth,
and as we have already mentioned, all fertile soils,
or soils capable of culture, contain alumina as an
invariable constituent. There must, therefore, be
something in aluminous earth which enables it to
exercise an influence on the life of plants, and to
assist in their development. The property on
which this depends is that of its invariably con-
taining potash and soda.
Alumina exercises only an indirect influence on
vegetation, by its power of attracting and retaining
water and ammonia ; it is itself very rarely found
in the ashes of plants, but silica is always present,
having in most places entered the plants by means
of alkalies. In order to form a distinct conception
of the quantities of alkalies in aluminous minerals
it must be remembered that felspar contains I7f
per cent, of potash, albite 11*43 per cent, of soda,
and mica 3 — 5 per cent. ; and that zeolite con-
tains 13 — 16 per cent, of both alkalies taken
together. The late analyses of Ch. Gmelin,
Lowe, Fricke, Meyer, and Redtenbacher, have
also shown, that basalt contains from f to 3 per
cent, of potash, and from 5 — 7 per cent, of soda,
that clay-slate contains from 2*75 — 3*31 per
cent, of potash, and loam from 1^ — 4 per cent, of
potash.
144 THE ART OF CULTURE.
If, now, we calculate from these data, and from
the specific weights of the different substances,
how much potash must be contained in a layer of
soil, which has been formed by the disintegration
of 40,000 square feet (1 Hessian acre) of one of
these rocks to the depth of 20 inches, we find that
a soil of
Felspar contains 1,152,000 Ibs.
Clink-stone , from 200,000 to 400,000 ,,
Basalt
Clay-slate
Loam
47,500 „ 75,000 „
100,000',, 200,000 „
87,000 „ 300,000 „
Potash is present in all clays ; according to Fuchs,
it is contained even in marl ; it has been found in
all the argillaceous earths in which it has been
sought. The fact that they contain potash may
be proved in the clays of the transition and strati-
fied mountains, as well as in the recent formations
surrounding Berlin, by simply digesting them with
sulphuric acid, by which process alum is formed.
(Mitscherlich.) It is well known also to all manu-
facturers of alum, that the leys contain a certain
quantity of this salt ready formed, the potash of
which has its origin from the ashes of the stone
and brown coal, which contain much argillaceous
earth.
When we consider this extraordinary distribu-
tion of potash over the surface of the earth, is it
reasonable to have recourse to the idea, that the
presence of this alkali in plants is due to the gene-
ration of a metallic oxide by a peculiar organic
OF THE FERTILITY OF SOILS. 145
process from the component parts of the atmo-
sphere. This opinion found adherents even after
the method of detecting potash in soils was known,
and suppositions of the same kind may be found
even in the writings of some physiologists of the
present day. Such opinions belong properly to
the time when flint was conceived to be a product
of chalk, and when everything, which appeared in-
comprehensible ,on account of not having been in-
vestigated, was explained by assumptions far more
i n comprehensible.
A thousandth part of loam mixed with the quartz
in new red sandstone, or with the lime in the dif-
ferent limestone formations, affords as much potash
to a soil only 20 inches in depth as is sufficient to
supply a forest of pines growing upon it for a cen-
tury. A single cubic foot of felspar is sufficient to
supply a wood, covering a surface of 40,000 square
feet, with the potash required for five years.
Land of the greatest fertility contains argilla-
ceous earths and other disintegrated minerals with
chalk and sand, in such a proportion as to give free
access to air and moisture. The land in the vicinity
of Vesuvius may be considered as the type of a
fertile soil, and its fertility is greater or less in dif-
ferent parts, according to the proportion of clay or
sand which it contains.
The soil which is formed by the disintegration of
lava cannot possibly, on account of its origin,
contain the smallest trace of vegetable matter, and
L
146 THE ART OF CULTURE.
yet it is well known, that when the volcanic ashes
have been exposed for some time to the influence
of air and moisture, a soil is gradually formed in
which all kinds of plants grow with the greatest
luxuriance. This fertility is owing to the alkalies
which are contained in the lava, and which, by
exposure to the weather, are rendered capable
of being absorbed by plants. Thousands of
years have been necessary to convert stones and
rocks into the soil of arable land, and thousands
of years more will be requisite for their perfect
reduction^ that is for the complete exhaustion of
their alkalies.
We see from the composition of the water in
rivers, streamlets, and springs, how little rain-water
is able to extract alkali from a soil, even after a
term of years ; this water is generally soft, and the
common salt, which even the softest invariably
contains, proves that those alkaline salts, which are
carried to the sea by rivers and streams, are
returned again to the land by wind and rain.
Nature itself shows us what plants require at the
commencement of the development of their germs
and first radicle fibres. Bequerel has shown that
the graminece, leguminostz, crucifertz, cichoracece,
unibellifercz, coniferce, and cmurbitacece emit
acetic acid during germination. A plant which has
just broken through the soil, and a leaf just burst
open from the bud, furnish ashes by incineration,
which contain as much, and 'generally more, of
OF THE FERTILITY OF SOILS. 147
alkaline salts than at any period of their life.
(De Saussure). Now we know also from the experi-
ments of Bequerel in what manner these alkaline
salts enter young plants ; the acetic acid formed
during germination is diffused through the wet or
moist soil, becomes saturated with lime, magnesia,
and alkalies, and is again absorbed by the radicle
fibres in the form of neutral salts. After the ces-
sation of life, when plants are subjected to decom-
position by means of decay and putrefaction, the
soil receives again that which had been extracted
from it.
Let us suppose that a soil has been formed by the
action of the weather on the component parts of
granite, grauwacke, mountain limestone, or por-
phyry, and that nothing has vegetated for thousands
of years. Now this soil would have become a
magazine of alkalies, in a condition favourable for
their assimilation by the roots of plants.
The interesting experiments of Struve have
proved that water impregnated with carbonic acid
decomposes rocks which contain alkalies, and then
dissolves a part of the alkaline carbonates. It is
evident that plants, also, by producing carbonic
acid during their decay, and by means of the acids
which exude from their roots in the living state,
contribute no less powerfully to destroy the cohe-
rence of rocks. Next to the action of air, water,
and change of temperature, plants themselves are
L 2
148 THE ART OF CULTURE.
the most powerful agents in effecting the disinte-
gration of rocks.
Air, water, and the change of temperature
prepare the different species of rocks for yielding
to plants the alkalies which they contain. A soil
which has been exposed for centuries to all the
influences which effect the disintegration of rocks,
but from which the alkalies have not been removed,
will be able to afford the means of nourishment to
those vegetables which require alkalies for its
growth during many years ; but it must gradually
become exhausted, unless those alkalies which have
been removed are again replaced ; a period, there-
fore, will arrive, when it will be necessary to expose
it, from time to time, to a further disintegration, in
order to obtain a new supply of soluble alkalies.
For small as is the quantity of alkali which plants
require, it is nevertheless quite indispensable for
their perfect development. But when one or more
years have elapsed without any alkalies having been
extracted from the soil, a new harvest may be
expected.
The first colonists of Virginia found a country,
the soil of which was similar to that mentioned
above ; harvests of wheat and tobacco were obtained
for a century from one and the same field without
the aid of manure, but now whole districts are
converted into unfruitful pasture land, which with-
out manure produces neither wheat nor tobacco.
OF THE FERTILITY OF SOILS. 149
From every acre of this land, there were removed
in the space of one hundred years 1200 Ibs. of
alkalies in leaves, grain, and straw ; it became
unfruitful therefore, because it was deprived of
every particle of alkali, which had been reduced to
a soluble state, and because that which was rendered
soluble again in the space of one year, was not
sufficient to satisfy the demands of the plants.
Almost all the cultivated land in Europe is in this
condition ; fallow is the term applied to land left at
rest for further disintegration. It is the greatest
possible mistake to suppose that the temporary
diminution of fertility in a soil is owing to the loss
of humus ; it is the mere consequence of the
exhaustion of the alkalies.
Let us consider the condition of the country
around Naples, which is famed for its fruitful corn-
land ; the farms and villages are situated from 1 8
to 24 miles distant from one another, and between
them there are no roads, and consequently no
transportation of manure. Now corn has been
cultivated on this land for thousands of years,
without any part of that which is annually removed
from the soil being artificially restored to it. How
can any influence be ascribed to humus under such
circumstances, when it is not even known whether
.humus was ever contained in the soil ?
The method of culture in that district completely
explains the permanent fertility. It appears very
bad in the eyes of our agriculturists, but there it is
150 THE ART OF CULTURE.
the best plan which could be adopted. A field is
cultivated once every three years, and is in the inter-
vals allowed to serve as a sparing pasture for cattle.
The soil experiences no change in the two years
during which it there lies fallow, further than that
it is exposed to the influence of the weather, by
which a fresh portion of the alkalies contained in it
are again set free or rendered soluble. The animals
fed on these fields yield nothing to these soils
which they did not formerly possess. The weeds
upon which they live spring from the soil, and that
which they return to it as excrement, must always
be less than that which they extract. The field,
therefore, can have gained nothing from the mere
feeding of cattle upon them ; on the contrary, the
soil must have lost some of its constituents.
Experience has shown in agriculture, that wheat
should not be cultivated after wheat on the same
soil, for it belongs with tobacco to the plants which
exhaust a soil. But if the humus of a soil gives it
the power of producing corn, how happens it that
wheat does not thrive in many parts of Brazil,
where the soils are particularly rich in this sub-
stance, or in our own climate, in soils formed of
mouldered wood ; that its stalk under these cir-
cumstances attains no strength, and droops prema-
turely? The cause is this, — that the strength of
the stalk is due to silicate of potash, and that the
corn requires phosphate of magnesia, neither of
which substances a soil of humus can afford, since
OF THE FERTILITY OF SOILS. 151
it does not contain them ; the plant may indeed,
under such circumstances, become an herb, but
will not bear fruit.
Again, how does it happen that wheat does not
flourish on a sandy soil, and that a calcareous soil
is also unsuitable for its growth, unless it be not
mixed with a considerable quantity of clay ? It is
because these soils do not contain alkalies in suffi-
cient quantity, the growth of wheat being arrested
by this circumstance, even should all other sub-
stances be presented in abundance.
It is not mere accident that only trees of the fir
tribe grow on the sandstone and limestone of the
Carpathian mountains and the Jura, whilst we find
on soils of gneiss, mica-slate, and granite in Bavaria,
of clinkstone on the Rhone, of basalt in Vogelsberge,
and of clay-slate on the Rhine and Eifel, the finest
forests of other trees which cannot be produced on
the sandy or calcareous soils upon which pines
thrive. It is explained by the fact, that trees, the
leaves of which are renewed annually, require
for their leaves six to ten times more alkalies than
the fir-tree or pine, and hence, when they are
placed in soils in which alkalies are contained in
very small quantity, do not attain maturity.* When
we see such trees growing on a sandy or calcareous
* One thousand parts of the dry leaves of oaks yielded 55 parts of
ashes, of which 24 parts consisted of alkalies soluble in water ; the same
quantity of pine leaves gave only 29 parts of ashes, which contained
4-6 parts of soluble salts. (De Saussure.)
152 THE ART OF CULTURE.
soil— the red-beech, the service-tree, and the wild-
cherry, for example, thriving luxuriantly on lime-
stone, we may be assured that alkalies are present
in the soil, for they are necessary to their existence.
Can we, then, regard it as remarkable, that such
trees should thrive in America, on those spots on
which forests of pines which have grown and col-
lected alkalies for centuries, have been burnt, and
to which the alkalies are thus at once restored ; or
that the Spartiwn scoparium, Erysimum latifolium,
Blitum capitatum, Senecio viscosus, plants remark-
able for the quantity of alkalies contained in their
ashes, should grow with the greatest luxuriance on
the localities of conflagrations.*
Wheat will not grow on a soil which has produced
wormwood, and, vice versa, wormwood does not
thrive where wheat has grown, because they are
mutually prejudicial by appropriating the alkalies
of the soil.
One hundred parts of the stalks of wheat yield
15*5 parts of ashes (H. Davy] ; the same quantity of
the dry stalks of barley, 8' 54 parts (Schroder) ; and
one hundred parts of the stalks of oats, only 4*42 ;
— the ashes of all these are of the same composition.
We have in these facts a clear proof of what
* After the great fire in London, large quantities of the En/simum
latifolium were observed growing on the spots where a fire had taken
place. On a similar occasion, the BHtum capitatnm was seen at Copen-
hagen, the Senecio viacosus in Nassau, and the Spartium scoparium in
Languedoc. After the burnings of forests of pines in North America
poplars grew on the same soil. (Franklin.}
OF THE FERTILITY OF SOILS. 153
plants require for their growth. Upon the same
field, which will yield only one harvest of wheat,
two crops of barley and three of oats may be
raised.
All plants of the grass kind require silicate of
potash. Now this is conveyed to the soil, or ren-
dered soluble in it by the irrigation of meadows.
The equisetacece, the reeds and species of cane, for
example, which contain such large quantities of
siliceous earth, or silicate of potash, thrive luxuri-
antly in marshes, in argillaceous soils, and in ditches,
streamlets, and other places, where the change of
water renews constantly the supply of dissolved si-
lica. The amount of silicate of potash removed from
a meadow, in the form of hay, is very considerable.
We need only call to mind the melted vitreous mass
found on a meadow between Manheim and Heidel-
berg after a thunder-storm. This mass was at first
supposed to be a meteor, but was found on exami-
nation (by Gmeliri) to consist of silicate of potash ;
a flash of lightning had struck a stack of hay, and
nothing was found in its place except 'the melted
ashes of the hay.
Potash is not the only substance necessary for
the existence of most plants, indeed it has been
already shown that the potash may be replaced, in
many cases, by soda, magnesia, or lime ; but other
substances, besides alkalies, are required to sustain
the life of plants.
Phosphoric acid has been found in the ashes of
154 THE ART OF CULTURE.
all plants hitherto examined, and always in combi-
nation with alkalies or alkaline earths. Most seeds
contain certain quantities of phosphates. In the
seeds of different kinds of corn, particularly, there
is abundance of phosphate of magnesia.
Plants obtain their phosphoric acid from the soil.
It is a constituent of all land capable of cultiva-
tion, and even the heath at Liineburg contains it
in appreciable quantity. Phosphoric acid has been
detected, also, in all mineral waters in which its
presence has been tested ; and in those in which
it has not been found, it has not been sought for.
The most superficial strata of the deposits of sul-
phuret of lead (galena) contain crystallized phos-
phate of lead (greenlead ore)-, clay-slate, which forms
extensive strata, is covered in many places with
crystals of phosphate of alumina ( Wavellite) ; all its
fractured surfaces are overlaid with it. Phosphate
of lime (Apatite) is found even in the volcanic bowl-
ders on the Laacher See in the Eifel, near Ander-
nach.
The soil in which plants grow furnishes them
with phosphoric acid, and they in turn yield it to
animals, to be used in the formation of their bones,
and of those constituents of the brain which con-
tain phosphorus. Much more phosphorus is thus
afforded to the body than it requires, when flesh,
bread, fruit, and husks of grain are used for food,
and this excess in them is eliminated in the urine
and the solid excrements. We may form an idea
OF THE FERTILITY OF SOILS. 155
of the quantity of phosphate of magnesia contained
in grain, when we consider that the concretions in
the coscum of horses consist of phosphate of mag-
nesia and ammonia, which must have been obtained
from the hay and oats consumed as food. Twenty-
nine of these stones were taken after death from the
rectum of a horse belonging to a miller in Eber-
stadt, the total weight of which amounted to 3lbs. ;
and Dr. F. Simon has lately described a similar
concretion found in the horse of a carrier, which
weighed l^lb.
It is evident that the seeds of corn could not be
formed without phosphate of magnesia, which is
one of their invariable constituents ; the plant
could not under such circumstances reach maturity.
Some plants, however, extract other matters
from the soil besides silica, potash, and phosphoric
acid, which are essential constituents of the plants
ordinarily cultivated. These other matters, we
must suppose, supply, in part at least, the place
and perform the function of the substances just
named. We may thus regard common salt, sul-
phate of potash, nitre, chloride of potassium, and
other matters, as necessary constituents of several
plants.
Clay-slate contains generally small quantities of
oxide of copper ; and soils formed from micaceous
schist contain some metallic fluorides. Now, small
quantities of these substances also are absorbed
156 THE ART OF CULTURE.
into plants, although we cannot affirm that they
are necessary to them.
It appears that, in certain cases, fluoride of cal-
cium may take the place of the phosphate of lime
in the bones and teeth ; at least, it is impossible
otherwise to explain its constant presence in the
bones of antediluvian animals, by which they are
distinguished from those of a later period. The
bones of human skulls found at Pompeii contain as
much fluoric acid as those of animals of a former
world, for if they be placed in a state of powder in
glass vessels, and digested with sulphuric acid, the
interior of the vessel will, after twenty -four hours,
be found powerfully corroded, (Liebig) ; whilst the
bones and teeth of animals of the present day
contain only traces of it, (Berzelius).
De Saussure remarked, that plants require
unequal quantities of the component parts of soils
in different stages of their development ; an obser-
vation of much importance in considering the
growth of plants. Thus, wheat yielded y^fo of
ashes a month before blossoming, TtHhr while in blos-
som, and TO oo~ after the ripening of the seeds. It is
therefore, evident, that wheat from the time of its
flowering restores a part of its organic constituents
to the soil, although the phosphate of magnesia
remains in the seeds.
The fallow-time, as we have already shown, is
that period of culture, during which land is exposed
FALLOW-CROPS. 15/
to a progressive disintegration by means of the
influence of the atmosphere, for the purpose of
rendering a certain quantity of alkalies capable of
being appropriated by plants.
Now, it is evident, that the careful tilling of fallow
land must increase and accelerate this disintegra-
tion. For the purpose of agriculture, it is quite
indifferent, whether the land is covered with weeds,
or with a plant which does not abstract the potash
inclosed in it. Now many plants in the family of the
leguminosce, are remarkable on account of the small
quantity of alkalies or salts in general, which they
contain; the Vicia faba, for example, contains no
free alkalies, and not one per cent, of the phos-
phates of lime and magnesia (Eirikof). The bean
of the Phaseolus Vulgaris contains only traces of
salts (Braconnot). The stem of the Medicago sativa
contains only 0*83 per cent., that of the Ervum lens
only 0*57 of phosphate of lime with albumen
(Crome). Buck-wheat dried in the sun yields only
0*681 per cent, of ashes, of which 0*09 parts are
soluble salts (Zenneck)* These plants belong to
those which are termed fallow-crops, and the cause
wherefore they do not exercise any injurious influ-
ence on corn which is cultivated immediately after
* The small quantity of phosphates which the seeds of the lentils,
beans and peas contain, must be the cause of their small value as articles
of nourishment, since they surpass all other vegetable food in the
quantity of nitrogen which enters into their composition. But as the
component parts of the bones (phosphate of lime and magnesia) are
absent, they satisfy the appetite without increasing the strength.
158 THE ART OF CULTURE.
them is, that they do not extract the alkalies of the
soil, and only a very small quantity of phosphates.
It is evident that two plants growing beside each
other will mutually injure one another, if they
withdraw the same food from the soil. Hence it
is not surprising that the Matricaria chamomilla,
and Spartium scoparium, impede the growth of
corn, when it is considered that both yield from
7 to 7*43 per cent, of ashes, which contain •£$ of
carbonate of potash. The darnel, and the Erigeron
acre, blossom and bear fruit at the same time as
the corn, so that when growing mingled with it,
they will partake of the component parts of the
soil, and in proportion to the vigour of their growth,
that of the corn must decrease ; for what one
receives, the others are deprived of. Plants will,
on the contrary, thrive beside each other, either
when the substances necessary for their growth
which they extract from the soil are of different
kinds, or when they themselves are not both
in the same stages of development at the same
time.
On a soil, for example, which contains potash,
both wheat and tobacco may be reared in succes-
sion, because the latter plant does not require
phosphates, salts which are invariably present in
wheat, but requires only alkalies, and food con-
taining nitrogen.
According to the analysis of Posselt and jReimann,
10,000 parts of the leaves of the tobacco-plant
INTERCHANGE OF CROPS. 159
contain 16 parts of phosphate of lime, 8*8 parts of
silica, and no magnesia ; whilst an equal quantity
of wheat-straw contains 47*3 parts, and the same
quantity of the grain of wheat 99'45 parts of phos-
phates (De Saussure).
Now, if we suppose that the grain of wheat is
equal to half the weight of its straw, then the quan-
tity of phosphates extracted from a soil by the same
weights of wheat and tobacco must be as 97*7 : 16.
This difference is very considerable. The roots of
tobacco, as well as those of wheat, extract the phos-
phates contained in the soil, but they restore them
again, because they are not essentially necessary to
the development of the plant.
OF THE INTERCHANGE OF CROPS, AND OF
MANURE.
It has long since been found by experience, that
the growth of annual plants is rendered imperfect,
and their crops of fruit or herbs less abundant,
by cultivating them in successive years on the same
soil, and that, in spite of the loss of time, a greater
quantity of grain is obtained, when afield is allowed
to be uncultivated for a year. During this interval
of rest, the soil, in a great measure, regains its
original fertility.
It has been further observed, that certain plants,
such as peas, clover, and flax, thrive on the same
soil only after a lapse of years ; whilst others, such
as hemp, tobacco, helianthus tuberosus, rye, and
160 INTERCHANGE OF CROPS.
oats, may be cultivated in close succession when
proper manure is used. It has also been found,
that several of these plants improve the soil, whilst
others, and these are the most numerous, impove-
rish or exhaust it. Fallow turnips, cabbage, beet,
spelt, summer and winter barley, rye, and oats, are
considered to belong to the class which impoverish
a soil ; whilst by wheat, hops, madder, late turnips,
hemp, poppies, teasel, flax, weld, and licorice, it is
supposed to be entirely exhausted.
The excrements of man and animals have been
employed from the earliest times for the purpose of
increasing the fertility of soils ; and it is com-
pletely established by all experience, that they
restore certain constituents to the soil, which
are removed with the roots, fruit, or grain, or entire
plants grown upon it.
But it has been observed that the crops are not
always abundant in proportion to the quantity of
manure employed, even although it may have been
of the most powerful kind ; that the produce of
many plants, for example, diminishes, in spite
of the apparent replacement of the substances re-
moved from the soil by manure, when they are
cultivated on the same field for several years in
succession.
On the other hand it has been remarked, that a
field which has become unfitted for a certain kind
of plants was not on that account unsuited for
another; and upon this observation, a system of
THEORIES OF ITS JUSE. 161
agriculture has been gradually founded, the prin-
cipal object of which is to obtain the greatest
possible produce with the least expense of manure.
Now it was deduced from all the foregoing facts
that plants require for their growth different con-
stituents of soil, and it was very soon perceived,
that an alternation of the plants cultivated main-
tained the fertility of a soil quite as well as leaving
it at rest or fallow. It was evident that all plants
must give back to the soil in which they grow
different proportions of certain substances, which
are capable of being used as food by a succeeding
generation.
But agriculture has hitherto never sought aid
from chemical principles, based on the knowledge
of those substances which plants extract from the
soil on which they grow, and of those restored to
the soil by means of manure. The discovery of
such principles will be the task of a future genera-
tion, for what can be expected from the present,
which recoils with seeming distrust and aversion
from all the means of assistance offered it by
chemistry, and which does not understand the
art of making a rational application of chemical
discoveries ? A future generation, however, will
derive incalculable advantage from these means of
help.
Of all the views which have been adopted regard-
ing the cause of the favourable effects of the alter-
nations of crops, that proposed by M. Decandolle
M
162 THE INTERCHANGE OF CROPS.
alone deserves to be mentioned as resting on a firm
basis.
Decandolle supposes that the roots of plants
imbibe soluble matter of every kind from the soil,
and thus necessarily absorb a number of substances
which are not adapted to the purposes of nutrition,
and must subsequently be expelled by the roots,
and returned to the soil as excrements. Now as
excrements cannot be assimilated by the plant
which ejected them, the more of these matters
which the soil contains, the more unfertile must it
be for plants of the same species. These excre-
mentitious matters may, however, still be capable of
assimilation by another kind of plants, which would
thus remove them from the soil, and render it again
fertile for the first. And if the plants last grown
also expel substances from their roots, which can
be appropriated as food by the former, they will
improve the soil in two ways.
Now a great number of facts appear at first sight
to give a high degree of probability to this view.
Every gardener knows that a fruit-tree cannot be
made to grow on the same spot where another of
the same species has stood ; at least not until after
a lapse of several years. Before new vine-stocks are
planted in a vineyard from which the old have been
rooted out, other plants are cultivated on the soil for
several years. In connexion with this it has been
observed, that several plants thrive best when
growing beside one another ; and on the contrary,
THEORIES OF ITS USE. 163
that others mutually prevent each other's develop-
ment. Whence it was concluded, that the bene-
ficial influence in the former case depended on a
mutual interchange of nutriment between the
plants, and the injurious one in the latter on a
poisonous action of the excrements of each on the
other respectively.
A series of experiments by Macaire-Princep
gave great weight to this theory. He proved
beyond all doubt that many plants are capable of
emitting extractive matter from their roots. He
found that the excretions were greater during the
night than by day (?), and that the water in which
plants of the family of the Leguminosce grew, acquired
a brown colour. Plants of the same species, placed
in water impregnated with these excrements, were
impeded in their growth, and faded prematurely,
whilst, on the contrary, corn-plants grew vigor-
ously in it, and the colour of the water diminished
sensibly ; so that it appeared, as if a certain quan-
tity of the excrements of the Leguminosce had
really been absorbed by the corn-plants. These
experiments afforded as their main result, that the
characters and properties of the excrements of dif-
ferent species of plants are different from one
another, and that some plants expel excrementitious
matter of an acrid and resinous character ; others
mild (douce) substances resembling gum. The
former of these, according to Macaire- Princep, may
be regarded as poisonous, the latter as nutritious.
M 2
164 THE INTERCHANGE OF CROPS.
The experiments ofMacaire-Princep are positive
proof that the roots, probably of all plants, expel
matters, which cannot be converted in their
organism either into woody fibre, starch, vegetable
albumen, or gluten, since their expulsion indicates
that they are quite unfitted for this purpose. But
they cannot be considered as a confirmation of the
theory of Decandolle, for they leave it quite unde-
cided whether the substances were extracted from
the soil, or formed by the plant itself from food
received from another source. It is certain that
the gummy and resinous excrements observed by
Macaire-Princep could not have been contained in
the soil ; arid as we know that the carbon of a soil is
not diminished by culture, but, on the contrary,
increased, we must conclude, that all excrements
which contain carbon must be formed from the
food obtained by plants from the atmosphere.
Now, these excrements are compounds, produced
in consequence of the transformations of the food,
and of the new forms which it assumes by entering
into the composition of the various organs.
M. Decandolle' s theory is properly a modifica-
tion of an earlier hypothesis, which supposed that
the roots of different plants extracted different
nutritive substances from the soil, each plant
selecting that which was exactly suited for its
assimilation. According to this hypothesis, the
matters incapable of assimilation are not extracted
from the soil, whilst M. Decandolle considers that
THEORIES OF ITS USE. 165
they are returned to it in the form of excrements.
Both views explain how it happens that after corn,
corn cannot be raised with advantage, nor after
peas, peas ; but they do not explain how a field is
improved by lying fallow, and this in proportion to
the care with which it is tilled and kept free from
weeds ; nor do they show how a soil gains carbon-
aceous matter by the cultivation of certain plants
such as lucern and esparsette.
Theoretical considerations on the process of nu-
trition, as well as the experience of all agricultur-
ists, so beautifully illustrated by the experiments of
Macaire-Princep, leave no doubt that substances
are excreted from the roots of plants, and that
these matters form the means by which the carbon
received from humus in the early period of their
growth, is restored to the soil. But we may now
inquire whether these excrements in the state in
which they are expelled, are capable of being em-
ployed as food by other plants.
The excrements of a carnivorous animal contain
no constituents fitted for the nourishment of another
of the same species ; but it is possible that an herbi-
vorous animal, a fish, or a fowl, might find in them
undigested matters, capable of being digested in
their organism, from the very circumstance of their
organs of digestion having a different structure.
This is the only sense in which we can conceive
that the excrements of one animal could yield
matter adapted for the nutrition of another.
166 THE INTERCHANGE OF CROPS.
A number of substances contained in the food of
animals pass through their alimentary organs with-
out change, and are expelled from the system ;
these are excrements but not excretions. Now a
part of such excrementitious matter might be as-
similated in passing through the digestive apparatus
of another animal. The organs of secretion form
combinations of which only the elements were con-
tained in the food. The production of these new
compounds is a consequence of the changes which
the food undergoes in becoming chyle and chyme,
and of the further transformations to which these
are subjected by entering into the composition of
the organism. These matters, likewise, are elimi-
nated in the excrements, which must therefore con-
sist of two different kinds of substances, namely, of
the indigestible constituents of the food, and of the
new compounds formed by the vital process.
The latter substances have been produced in con-
sequence of the formation of fat, muscular fibre,
cerebral and nervous substance, and are quite inca-
pable of being converted into the same substances
in any other animal organism.
Exactly similar conditions must subsist in the
vital processes of plants. When substances, which
are incapable of being employed in the nutrition of
a plant, exist in the matter absorbed by its roots,
they must be again returned to the soil. Such ex-
crements might be serviceable and even indispens-
able to the existence of several other plants. But
CAUSES OF ITS BENEFICIAL INFLUENCE. 167
substances that are formed in a vegetable organism
during the process of nutrition, which are produced,
therefore, in consequence of the formation of woody
fibre, starch, albumen, gum, acids, &c., cannot
again serve in any other plants to form the same
constituents of vegetables.
The consideration of these facts enables us to
distinguish the difference between the views of
Decandolle and those of Macaire-Princep. The
substances which the former physiologist viewed as
excrements, belonged to the soil ; they were undi-
gested matters, which although not adapted for the
nutrition of one plant, might yet be indispensable
to another. Those matters, on the contrary, de-
signated as excrements by Macaire-Princep, could
only in one form serve for the nutrition of vegeta-
bles. It is scarcely necessary to remark, that this
excrementitious matter must undergo a change be-
fore another season. During autumn and winter
it begins to suffer a change from the influence of
air and water ; its putrefaction, and at length, by
continued contact with the air, which tillage is the
means of procuring, its decay are effected ; and
at the commencement of spring it has become
converted, either in whole or in part, into a sub-
stance which supplies the place of humus, by being
a constant source of carbonic acid.
The quickness with which this decay of the excre-
ments of plants proceeds, depends on the composi-
tion of the soil, and on its greater or less porosity.
168 THE INTERCHANGE OF CROPS.
It will take place very quickly in a calcareous soil ;
for the power of organic excrements to attract oxy-
gen and to putrify, is increased by contact with the
alkaline constituents, and by the general porous
nature of such kinds of soil, which freely permit the
access of air. But it requires a longer time in
heavy soils consisting of loam or clay.
The same plants can be cultivated with advan-
tage on one soil after the second year., but in others
not until the fifth or ninth, merely on account of
the change and destruction of the excrements which
have an injurious influence on the plants being
completed in the one, in the second year ; in the
others not until the ninth.
In some neighbourhoods, clover will not thrive
till the sixth year ; in others not till the twelfth ;
flax in the second or third year. All this depends
on the chemical nature of the soil ; for it has been
found by experience, that in those districts where
the intervals at which the same plants can be
cultivated with advantage, are very long, the
time cannot be shortened even by the use of
the most powerful manures. The destruction
of the peculiar excrements of one crop must
have taken place before a new crop can be pro-
duced.
Flax, peas, clover, and even potatoes, are plants
the excrements of which, in argillaceous soils,
require the longest time for their conversion into
humus ; but it is evident, that the use of alkalies
CAUSES OF ITS BENEFICIAL INFLUENCE. 169
and burnt lime, or even small quantities of ashes
which have not been lixiviated, must enable a soil
to permit the cultivation of the same plants in a
much shorter time.
A soil lying fallow owes its earlier fertility, in
part, to the destruction or conversion into humus
of the excrements contained in it, which is effected
during the fallow season, at the same time that the
land is exposed to a further disintegration.
In the soils in the neighbourhood of the Rhine
and Nile, which contain much potash, and where
crops can be obtained in close succession from the
same field, the fallowing of the land is superseded
by the inundation ; the irrigation of meadows
effects the same purpose. It is because the water
of rivers and streams contains oxygen in solution,
that it effects the most complete and rapid putre-
faction of the excrements contained in the soil
which it penetrates, and in which it is continually
renewed. If it was the water alone which produced
this effect, marshy meadows should be the most
fertile.
It follows from what has preceded, that the
advantage of the alternation of crops is owing to
two causes.
A fertile, soil ought to afford to a plant all the
inorganic bodies indispensable for its existence in
sufficient quantity and in such condition as allows
their absorption.
All plants require alkalies, which are contained
170 THE INTERCHANGE OF CROPS.
in some, in the graminece for example, in the form
of silicates, in others, in that of tartrates, citrates,
acetates, or oxalates.
When these alkalies are in combination with
silicic acid, the ashes obtained by the incineration
of the plant contain no carbonic acid ; but when
they are united with organic acids, the addition of
a mineral acid to their ashes causes an effervescence.
A third species of plants requires phosphate of
lime, another, phosphate of magnesia, and several
do not thrive without carbonate of lime.
Silicic acid is the first solid substance taken up
by plants ; it appears to be the material from which
the formation of the wood takes its origin, acting
like a grain of sand around which the first crystals
form in a solution of a salt which is in the act of
crystallizing. Silicic acid appears to perform the
function of woody fibre in the Equisetacece and bam-
boos, just as the crystalline salt, oxalate of lime,
does in many of the lichens.
When we grow in the same soil for several years
in succession different plants, the first of which
leaves behind that which the second, and the
second that which the third may require, the soil
will be a fruitful one for all the three kinds of pro-
duce. If the first plant, for example, be wheat,
which consumes the greatest part of the silicate of
potash in a soil, whilst the plants which succeed it
are of such a kind as require only small quantities
of potash, as is the case with the Leguminosce,
CAUSES OF ITS BENEFICIAL INFLUENCE. \7 \
turnips, potatoes, &c. ; the wheat may be again
sowed with advantage after the fourth year ; for,
during the interval of three years, the soil will, by
the action of the atmosphere, be rendered capable
of again yielding silicate of potash in sufficient
quantity for the young plants.
The same precautions must be observed with
regard to the other inorganic constituents, when it
is desired to grow different plants in succession on
the same soil ; for a successive growth of plants
which extract the same component parts, must
gradually render it incapable of producing them.
Each of these plants, during its growth, returns to
the soil a certain quantity of substances containing
carbon, which are gradually converted into humus,
and are for the most part equivalent to as much
carbon as the plants had formerly extracted from
the soil in the state of carbonic acid. But although
this is sufficient to bring many plants to maturity,
it is not enough to furnish their different organs
with the greatest possible supply of nourishment.
Now the object of agriculture is to produce either
articles of commerce, or food for man and animals,
but a maximum of produce in plants is always in
proportion to the quantity of nutriment supplied to
them in the first stage of their development.
The nutriment of young plants consists of car-
bonic acid, contained in the soil in the form of
humus, and of nitrogen in the form of ammonia,
both of which must be supplied to the plants if the
1/2 THE INTERCHANGE OF CROPS.
desired purpose is to be accomplished. The forma-
tion of ammonia cannot be effected on cultivated
land, but humus may be artificially produced ; and
this must be considered as an important object in
the alternation of crops, and as the second reason
of its peculiar advantages.
The sowing of a field with fallow plants, such as
clover, rye, buck- wheat, &c. and the incorporation
of the plants, when nearly at blossom, with the
soil, affect this supply of humus in so far, that
young plants subsequently growing in it find, at a
certain period of their growth, a maximum of nu-
triment, that is, matter in the process of decay.
The same end is obtained, but with much greater
certainty, when the field is planted with esparsette
or lucern. These plants are remarkable on account
of the great ramification of their roots, and strong
development of their leaves, and for requiring only
a small quantity of inorganic matter. Until they
reach a certain period of their growth, they retain
all the carbonic acid and ammonia which may have
been conveyed to them by rain and the air, for that
which is not absorbed by the soil is appropriated
by the leaves : they also possess an extensive four or
six fold surface capable of assimilating these bodies,
and of preventing the volatilization of the ammonia
from the soil, by completely covering it in.
An immediate consequence of the production of
the green principle of the leaves, and of their
remaining component parts, as well as of those of
CAUSES OF ITS BENEFICIAL INFLUENCE. 173
the stem, is the equally abundant excretion of
organic matters into the soil from the roots.
The favourable influence which this exercises on
the land, by furnishing it with matter capable of
being converted into humus lasts for several years,
but barren spots gradually appear after the lapse of
some time. Now, it is evident, that after from six
to seven years the ground must become so impreg-
nated with excrements that every fibre of the root
will be surrounded with them. As they remain for
some time in a soluble condition, the plants must
absorb part of them and suffer injurious effects in
consequence, because they are not capable of assi-
milation. When such a field is observed for several
years, it is seen, that the barren spots are again
covered with vegetation, (the same plants being
always supposed to be grown,) whilst new spots
become bare and apparently unfruitful, and so on
alternately. The causes which produce this alter-
nate barrenness and fertility in the different parts
of the land are evident. The excrements upon the
barren spots receiving no new addition, and being
subjected to the influence of air and moisture, they
pass into putrefaction, and their injurious influence
ceases. ' The plants now find those substances,
which formerly prevented their growth, removed,
and in their place meet with humus, that is,
vegetable matter in the act of decay.
We can scarcely suppose a better means of pro-
ducing humus than by the growth of plants, the
174 OF MANURE.
leaves of which are food for animals ; for they pre-
pare the soil for plants of every other kind, but par-
ticularly for those to which, as to rape and flax, the
presence of humus is the most essential condition
of growth.
The reasons why this interchange of crops is so
advantageous, — the principles which regulate this
part of agriculture, are, therefore, the artificial pro-
duction of humus, and the cultivation of different
kinds of plants upon the same field, in such an order
of succession, that each shall extract only certain
components of the soil, whilst it leaves behind
or restores those which a second or third species of
plant may require for its growth and perfect deve-
lopment.
Now, although the quantity of humus in a soil
may be increased to a certain degree by an artifi-
cial cultivation, still, in spite of this, there cannot
be the smallest doubt that a soil must gradually
lose those of its constituents which are removed
in the seeds, roots, and leaves of the plants raised
upon it. The fertility of a soil cannot remain un-
impaired, unless we replace in it all those substances
of which it has been thus deprived.
Now this is effected by manure.
When it is considered that every constituent of
the body of man and animals is derived from plants,
and that not a single element is generated by the
vital principle, it is evident that all the inorganic
constituents of the animal organism must be re-
COMPOSITION OF ANIMAL MANURES. 175
garded, in some respect or other, as manure.
During their life, the inorganic components of
plants which are not required by the animal system,
are disengaged from the organism, in the form of
excrements. After their death, their nitrogen and
carbon pass into the atmosphere as ammonia and
carbonic acid, the products of their putrefaction*
and at last nothing remains except the phosphate
of lime and other salts in their bones. Now this
earthy residue of the putrefaction of animals must
be considered, in a rational system of agriculture,
as a powerful manure for plants, because that which
has been abstracted from a soil for a series of years
must be restored to it, if the land is to be kept in
a permanent condition of fertility.
We may now inquire whether the excrements of
animals, which are employed as manure, are all of
a like nature and power, and whether they, in every
case, administer to the necessities of a plant by an
identical mode of action. These points may easily
be determined by ascertaining the composition of
the animal excrements, because we shall thus learn
what substances a soil really receives by their
means. According to the common view, the action
of solid animal excrements depends on the decaying
organic matters which replace the humus, and on
the presence of certain compounds of nitrogen,
which are supposed to be assimilated by plants, and
employed in the production of gluten and other
azotised substances. But this view requires further
176 OF MANURE.
confirmation with respect to the solid excrements
of animals, for they contain so small a proportion
of nitrogen, that they cannot possibly by means of
it exercise any influence upon vegetation.
We may form a tolerably correct idea of the
chemical nature of animal excrement without
further examination, by comparing the excrements
of a dog with its food. When a dog is fed with
flesh and bones, both of which consist in great part
of organic substances containing ^nitrogen, a moist
white excrement is produced which crumbles
gradually to a dry powder in the air. This excre-
ment consists of the phosphate of lime of the bones,
and contains scarcely y^o Par^ of its weight of
foreign organic substances. The whole process of
nutrition in an animal consists in the progressive
extraction of all the nitrogen from the food, so that
the quantity of this element found in the excre-
ments must always be less than that contained in
the nutriment. The analysis of the excrements of
a horse by Macaire and Marcet proves this fact
completely. The portion of excrements subjected
to analysis was collected whilst fresh, and dried
in vacuo over sulphuric acid ; 1 00 parts of it (cor-
responding to from 350 to 400 parts of the dung
before being dried) contained 0*8 of nitrogen.
Now every one who has had experience in this
kind of analysis is aware that a quantity under one
per cent, cannot be determined with accuracy. We
should, therefore, be estimating its proportion at a
COMPOSITION OF ANIMAL MANURES. 177
maximum., were we to consider it as equal to one-
half per cent. It is certain, however, that these
excrements are not entirely free from nitrogen, for
they emit ammonia when digested with caustic
potash.
The excrements of a cow, on combustion with
oxide of copper, yielded a gas which contained one
vol. of nitrogen gas, and 26*30 vol. of carbonic
acid.
100 parts of fresh excrements contained
Nitrogen . . . 0'506
Carbon . . . 6-204
Hydrogen . . . 0'824
Oxygen . . .4-818
Ashes . . . 1-748
Water . . . 85-900
100-000
Now, according to the analysis of Boussingault,
which merits the greatest confidence, hay contains
one per cent, of nitrogen ; consequently in the 25
Ibs. of hay which a cow consumes daily, \ of a Ib.
of nitrogen must have been assimilated. This
quantity of nitrogen entering into the composition
of muscular fibre would yield 8*3 Ibs. of flesh in its
natural condition*. The daily increase in size of a
cow is, however, much less than this quantity.
We find that the nitrogen, apparently deficient,
is actually contained in the milk and urine of the
* 100 Ibs of flesh contain on an average 15-86 of muscular fibre : 18
parts of nitrogen are contained in 100 parts of the latter.
N
178 OF MANURE.
animal. The urine of a milch-cow contains less
nitrogen than that of one which does not yield
milk ; and as long as a cow yields a plentiful supply
of milk, it cannot be fattened. We must search
for the nitrogen of the food assimilated not in the
solid, but in the liquid excrements. The influence
which the former exercise on the growth of vege-
tables does not depend upon the quantity of nitro-
gen which they contain. For if this were the
case, hay should possess the same influence ; that
is, from 20 to 25 Ibs. ought to have the same power
as 100 Ibs. of fresh cow-dung. But this is quite
opposed to all experience.
Which then are the substances in the excrements
of the cow and horse which exert an influence on
vegetation ?
When horse's-dung is treated with water, a por-
tion of it to the amount of 3 or 3^ per cent, is
dissolved, and the water is coloured yellow. The
solution is found to contain phosphate of magnesia,
and salts of soda, besides small quantities of organic
matters. The portion of the dung undissolved by
the water yields to alcohol a resinous substance pos-
sessing all the characters of gall which has under-
gone some change ; while the residue possesses the
properties of sawdust, from which all soluble matter
has been extracted by water, and burns without
any smell. 100 parts of the fresh dung of a horse
being dried at 100° C. (212° F.) leave from 25 to 30
or 31 parts of solid substances, and contained, ac-
ITS ESSENTIAL ELEMENTS. 179
eordingly,from 69 to 75 parts of water. From the
dried excrements, we obtain, by incineration, varia-
ble quantities of salts and earthy matters according
to the nature of the food which has been taken by
the animal. Macaire and Marcet found 27 per cent,
in the dung analysed by them ; I obtained only 10
per cent, from that of a horse fed with chopped
straw, oats, and hay. It results then that with
from 3600 to 4000 Ibs of fresh horse's-dung, cor-
responding to 1000 Ibs of dry dung, we place on
the land from 2484 to 3000 Ibs. of water, and from
730 to 900 Ibs. of vegetable and altered gall, and
also from 100 to 270 Ibs of salts and other inor-
ganic substances.
The latter are evidently the substances to which
our attention should be directed, for they are the
same which formed the component parts of the hay5
straw, and oats, with which the horse was fed.
Their principal constituents are the phosphates of
lime and magnesia, carbonate of lime and silicate
of potash ; the first three of these preponderated in
the corn, the latter in the hay.
Thus in 1000 Ibs. of horse's-dung, we present to
a field the inorganic substances contained in 6000
Ibs. of hay, or 8300 Ibs. of oats, (oats containing
3*1 per cent, ashes according to De Saussure).
This is sufficient to supply 1^ crop of wheat with
potash and phosphates.
The excrements of cows, black cattle and sheep,
contain phosphate of lime, common salt, and silicate
N 2
180 OF MANURE.
of lime, the weight of which varies from 9 to 28 per
cent., according to the fodder which the animal
receives ; the fresh excrements of the cow contain
from 86 to 90 per cent, of water.
Human faeces have been subjected to an exact ana-
lysis by Berzelius. When fresh they contain, besides
f of their weight of water, nitrogen in very variable
quantity, namely, in the minimum 1^, in the maxi-
mum 5 per cent. In all cases, however, they were
richer in this element than were .the excrements of
other animals. Berzelius obtained by the incinera-
tion of 100 parts of dried excrements, 15 parts of
ashes, which were principally composed of the
phosphates of lime and magnesia.
It is quite certain that the vegetable constituents
of the excrements with which we manure our fields
cannot be entirely without influence upon the
growth of the crops on them, for they will decay,
and thus furnish carbonic acid to the young plants.
But it cannot be imagined that their influence is
very great, when it is considered that a good soil is
manured only once every six or seven years, or
once every eleven or twelve years, when esparsette
or lucern have been raised on it, that the quantity
of carbon thus given to the land corresponds to
only 5*8 per cent, of what is removed in the form of
herbs, straw, and grain, and further that the rain-
water received by a soil contains much more carbon
in the form of carbonic acid than these vegetable
constituents of the manure.
ITS ESSENTIAL ELEMENTS. 181
The peculiar action, then, of the solid excrements
is limited to their inorganic constituents, which
thus restore to a soil that which is removed in the
form of corn, roots, or grain. When we manure
land with the dung of the cow or sheep, we supply
it with silicate of potash and some salts of phos-
phoric acid. In human faeces we give it the phos-
phates of lime and magnesia ; and in those of the
horse, phosphate of magnesia, and silicate of potash.
In the straw which has served as litter, we add a
further quantity of silicate of potash and phos-
phates ; which, if the straw be putrified, are in
exactly the same condition in which they were
before being assimilated.
It is evident, therefore, that the soil of a field
will alter but little, if we collect and distribute the
dung carefully ; a certain portion of the phosphates,
however, must be lost every year, being removed
from the land with the corn and cattle, and this
portion will accumulate in the neighbourhood of
large towns. The loss thus suffered must be
compensated for in a well managed farm, and
this is partly done by allowing the fields to lie
in grass. In Germany, it is considered that for
every 100 acres of corn-land, there must, in
order to effect a profitable cultivation, be 20 acres
of pasture-land, which produce annually, on an
average, 500 Ibs. of hay. Now, assuming that the
ashes of the excrements of the animals fed with this
hay amount to 6*82 per cent,, then 341 Ibs. of the
182 OF MANURE.
silicate of lime and phosphates of magnesia and lime
must be yielded by these excrements, and will in a
certain measure compensate for the loss which the
corn-land had sustained. The absolute loss in the salts
of phosphoric acid, which are not again replaced, is
spread over so great an extent of surface, that it
scarcely deserves to be taken account of. But the loss
of phosphates is again replaced in the pastures by
the ashes of the wood used in our houses for fuel.
We could keep our fields in* a constant state
of fertility by replacing every year as much as
we remove from them in the form of produce ;
but an increase of fertility, and consequent in-
crease of crop, can only be obtained when we add
more to them than we take away. It will be found,
that of two fields placed under conditions otherwise
similar, the one will be most fruitful upon which
the plants are enabled to appropriate more easily
and in greater abundance those contents of the
soil which are essential to their growth and de-
velopment.
From the foregoing remarks it will readily be
inferred, that for animal excrements, other sub-
stances containing their essential constituents may
be substituted. In Flanders, the yearly loss of
the necessary matters in the soil is completely
restored by covering the fields with ashes of
wood or bones, which may or may not have been
lixiviated, and of which the greatest part consists
of phosphates of lime and magnesia. The great
THE USE OF WOOD ASHES. 183
importance of manuring with ashes has been long
recognised by agriculturists as the result of experi-
ence. So great a value, indeed, is attached to this
material in the vicinity of Marburg and in the
Wetterau,* that it is transported as a manure from
the distance of 18 or 24 miles. Its use will be at
once perceived, when it is considered that the
ashes, after having been washed with water, con-
tain silicate of potash exactly in the same propor-
tions as in straw (10 Si 03 + K O.), and that their
only other constituents are salts of phosphoric acid.
But ashes obtained from various kinds of trees are
of very unequal value for this purpose ; those from
oak-wood are the least, and those from beech the
most serviceable. The ashes of oak-wood contain
only traces of phosphates, those of beech the fifth
part of their weight, and those of the pine and fir
from 9 to 15 per cent. The ashes of pines from
Norway contain an exceedingly small quantity of
phosphates, namely, only 1*8 per cent, of phosphoric
acid. (Berthier.)
With every 100 Ibs. of the lixiviated ashes of
the beech which we spread over a soil, we furnish
as much phosphates as 460 Ibs. of fresh human" ex-
crements could yield. Again, according to the analy-
sis of De Samsure, \ 00 parts of the ashes of the
grain of wheat contain 32 parts of soluble, and 4 4 '5
of insoluble phosphates, in all 76*5 parts. Now the
* Two well-known agricultural districts ; the first in Hesse-Cassel,
the second in Hesse-Darmstadt. — TBANS.
184 OF MANURE.
ashes of wheat straw contain 11*5 per cent, of the
same salts; hence with every 100 Ibs. of the ashes of
the beech, we supply a field with phosphoric acid suf-
ficient for the production of 3820 Ibs. of straw (its
ashes being calculated at 4*3 per cent. De Saussure),
or for 15-18000 Ibs. of corn, the ashes of which
amount, according to De Saussure, to 1*3 per cent.
Bone manure possesses a still greater importance
in this respect. The primary sources from which
the bones of animals are derived are the hay,
straw, or other substances which they take as food.
Now if we admit that bones contain 55 per cent,
of the phosphates of lime and magnesia (Berzelius),
and that hay contains as much of them as wheat-
straw, it will follow that 8 Ibs. of bones contain as
much phosphate of lime as 1000 Ibs. of hay or
wheat-straw, and 2 Ibs. of it as much as 1000 Ibs.
of the grain of wheat or oats. These numbers ex-
press pretty exactly the quantity of phosphates
which a soil yields annually on the growth of hay
and corn. Now the manure of an acre of land
with 40 Ibs. of bone dust is sufficient to supply
three crops of wheat, clover, potatoes, turnips, &c.,
with phosphates. But the form in which they are
restored to a soil does not appear to be a matter of
indifference. For the more finely the bones are
reduced to powder, and the more intimately they
are mixed with the soil, the more easily are they
assimilated. The most easy and practical mode of
effecting their division is to pour over the bones,
in a state of fine powder, half of their weight of
BONE MANURE. 185
sulphuric acid diluted with three or four parts of
water, and after they have been digested for some
time, to add one hundred parts of water, and
sprinkle this mixture over the field before the
plough. In a few seconds, the free acids unite
with the bases contained in the earth, and a neutral
salt is formed in a very fine state of division. Ex-
periments instituted on a soil formed from grau-
wacke, for the purpose of ascertaining the action
of manure thus prepared, have distinctly shown
that neither corn, nor kitchen-garden plants, suffer
injurious effects in consequence, but that on the
contrary they thrive with much more vigour.
In the manufactories of glue, many hundred tons
of a solution of phosphates in muriatic acid are
yearly thrown away as being useless. It would be
important to examine whether this solution might
not be substituted for the bones. The free acid
would combine with the alkalies in the soil, espe-
cially with the lime, and a soluble salt would thus
be produced, which is known to possess a favour-
able action upon the growth of plants. This salt,
muriate of lime (or chloride of calcium), is one of
those compounds which attracts water from the
atmosphere with great avidity, and might supply
the place of gypsum in decomposing carbonate of
ammonia, with the formation of sal-ammoniac and
carbonate of lime. A solution of bones in muriatic
acid placed on land in autumn or in winter would,
therefore, not only restore a necessary constituent
186 OF MANURE.
of the soil, and attract moisture to it, but would
also give it the power to retain all the ammonia
which fell upon it dissolved in the rain during the
period of six months.
The ashes of brown coal and peat often contain
silicate of potash, so that it is evident that these
might completely replace one of the principal con-
stituents of the dung of the cow and horse, and
they contain alsp some phosphates. Indeed, they
are much esteemed in the Wetterau as manure for
meadows and moist land.
It is of much importance to the agriculturist,
that he should not deceive himself respecting the
causes which give the peculiar action to the sub-
stances just mentioned. It is known, that they
possess a very favourable influence on vegetation ;
and it is likewise certain, that the cause of this is
their containing a body, which, independently of
the influence which it exerts by virtue of its form,
porosity, and capability of attracting and retaining
moisture, also assists in maintaining the vital
processes in plants. If it be treated as an un-
fathomable mystery, the nature of this aid will
never be known.
In medicine, for many centuries, the mode of
actions of all remedies was supposed to be concealed
by the mystic veil of Isis, but now these secrets have
been explained in a very simple manner. An unpo-
etical hand has pointed out the cause of the wonderful
and apparently inexplicable healing virtues of the
PRINCIPLES OF ITS USE. 187
springs in Savoy., by which the inhabitants cured
their goitre ; it was shown, that they contain small
quantities of iodine. In burnt sponges used for the
same purpose, the same element was also detected.
The extraordinary efficacy of Peruvian bark was
found to depend on a small quantity of a crystalline
body existing in it, viz. quinine ; and the causes of
the various effects of opium were detected in as
many different ingredients of that drug.
Calico-printers used for a long time the solid
excrements of the cow, in order to brighten and
fasten colours on cotton goods ; this material
appeared quite indispensable, and its action was
ascribed to a latent principle which it had obtained
from the living organism. But since its action was
known to depend on the phosphates contained in it,
it has been completely replaced by a mixture of salts,
in which the principal constituent is phosphate of
soda.
Now all such actions depend on a definite cause,
by ascertaining which, we place the actions them-
selves at our command.
It must be admitted as a principle of agriculture,
that those substances which have been removed
from a soil must be completely restored to it, and
whether this restoration be effected by means of
excrements, ashes, or bones, is in a great measure
a matter of indifference. A time will come when
fields will be manured with a solution of glass
(silicate of potash), with the ashes of burnt straw,
188 OF MANURE.
and with salts of phosphoric acid, prepared in
chemical manufactories, exactly as at present medi-
cines are given for fever and goitre.
There are some plants which require humus and
do not restore it to the soil by their excrements ;
whilst others can do without it altogether, and
add humus to a soil which contains it in small
quantity. Hence, a rational system of agricul-
ture would employ all the humus at command for
the supply of the former, and not expend any of
it for the latter ; and would in fact make use of
them for supplying the others with humus.
We have now considered all that is requisite in a
soil, in order to furnish its plants with the materials
necessary for the formation of the woody fibre, the
grain, the roots, and the stem, and now proceed to the
consideration of the most important object of agri-
culture, viz. the production of nitrogen in a form
capable of assimilation — the production, therefore,
of substances containing this element. The leaves,
which nourish the woody matter, the roots, from
which the leaves are formed, and which prepare the
substances for entering into the composition of the
fruit, and, in short, every part of the organism of a
plant, contain azotised matter in very varying pro-
portions, but the seeds and roots are always
particularly rich in them.
Let us now examine in what manner the greatest
possible production of substances containing nitro-
gen can be effected. Nature, by means of the
IT SUPPLIES NITROGEN. 189
atmosphere, furnishes nitrogen to a plant in quan-
tity sufficient for its normal growth. Now its
growth must be considered as normal, when it pro-
duces a single seed, capable of reproducing the same
plant in the following year. Such a normal condi-
tion would suffice for the existence of plants, and
prevent their extinction, but they do not exist for
themselves alone ; the greater number of animals
depend on the vegetable world for food, and by
a wise adjustment of nature, plants have the
remarkable power of converting, to a certain
degree, all the nitrogen offered to them into nutri-
ment for animals.
We may furnish a plant with carbonic acid, and
all the materials which it may require, we may
supply it with humus in the most abundant quan-
tity, but it will not attain complete development
unless nitrogen is also afforded to it ; an herb will
be formed, but no grain, even sugar and starch
may be produced, but no gluten.
But when we give a plant nitrogen in con-
siderable quantity, we enable it to attract with
greater energy, from the atmosphere, the carbon
which is necessary for its nutrition, when that in
the soil is not sufficient ; we afford to it a means
of fixing the carbon of the atmosphere in its
organism.
We cannot ascribe much of the power of the
excrements of black cattle, sheep, and horses, to
the nitrogen which they contain, for its quantity is
190 OF MANURE.
too minute. But that contained in the faeces of
man is proportionably much greater, although by
no means constant. In the faeces of the inhabitants
of towns, for example, who feed on animal matter,
there is much more of this constituent than in
those of peasants, or of such people as reside in the
country. The faeces of those who live principally
on bread and potatoes are similar in composition
and properties to those of animals.
All excrements have in this respect a very variable
and relative value. Thus, those of black cattle and
horses, are of great use on soils consisting of lime
and sand, which contain no silicate of potash and
phosphates, whilst their value is much less when
applied to soils formed of argillaceous earth, basalt,
granite, porphyry, clinkstone, and even mountain-
limestone, because all these contain potash in con-
siderable quantity. In such soils human excrements
are extremely beneficial, and increase their fertility
in a remarkable degree ; they are, of course, as
advantageous for other soils also ; but for the
manure of those first mentioned, the excrements of
other animals are quite indispensable.
We possess only one other source of manure
which acts by its nitrogen, besides the faeces of
animals, — namely, the urine of man and animals.
Urine is employed as manure either in the liquid
state, or with the faeces which are impregnated with
it. It is the urine contained in them which gives
to the solid faeces the property of emitting ammonia,
COMPOSITION OF URINE. 191
a property which they themselves possess only in a
very slight degree.
When we examine what substances we add to a
soil by supplying it with urine, we find that this
liquid contains in solution ammoniacal salts, uric
acid, (a substance containing a large quantity of
nitrogen), and salts of phosphoric acid.
According to Berzelius 1000 parts of human
urine contain : —
Urea . . . . . 30-10
Free Lactic acid, Lactate of Ammonia, and
animal matter not separable from them 17*14
Uric acid .... 1-00
Mucus of the bladder . . . 0-32
Sulphate of Potash . . . 3- 71
Sulphate of Soda . . . .3-16
Phosphate of Soda . . . 2'94
Phosphate of Ammonia . . 1 65
Chloride of Sodium . . . 4-46
Muriate of Ammonia . . .1-50
Phosphates of Magnesia and Lime . . 1*00
Siliceous earth .... 0*03
Water .... 933-00
1000.00
If we subtract from the above the urea, lactate of
ammonia, free lactic acid, uric acid, the phosphate
and muriate of ammonia, 1 per cent, of solid mat-
ter remains, consisting of inorganic salts, which
must possess the same action when brought on a
field, whether they are dissolved in water or in urine.
Hence the powerful influence of urine must depend
upon its other ingredients, namely, the urea and
ammoniacal salts. The urea in human urine exists
192 OF MANURE.
partly as lactate of urea, and partly in a free state.
(Henry.) Now when urine is allowed to putrify
spontaneously, that is, to pass into that state in
which it is used as manure, all the urea in com-
bination with lactic acid is converted into lactate
of ammonia, and that which was free, into volatile
carbonate of ammonia.
In dung-reservoirs well constructed and protected
from evaporation, this carbonate of ammonia is
retained in the state of solution, and when the
putrified urine is spread over the land, a part of
the ammonia will escape with the water which eva-
porates, but another portion will be absorbed by
the soil, if it contains either alumina or iron ; but
in general, only the muriate, phosphate, and lactate
of ammonia remain in the ground. It is these
alone, therefore, which enable the soil to exercise
a direct influence on plants during the progress of
their growth, and not a particle of them escapes
being absorbed by the roots.
On account of the formation of this carbonate of
ammonia, the urine becomes alkaline, although it
is acid in ite natural state. When it is lost by
being volatilized in the air, which happens in most
cases, the loss suffered is nearly equal to one half
of the weight of the urine employed, so that if we
fix it, that is, if we deprive it of its volatility, we
increase its action twofold. The existence of car-
bonate of ammonia in putrified urine long since
suggested the manufacture of sal-ammoniac from
MODE OF APPLYING URINE. 193
this material. When the latter salt possessed
a high price, this manufacture was even carried
on by the farmer. For this purpose the liquid ob-
tained from dunghills was placed in vessels of iron,
and subjected to distillation ; the product of this
distillation was converted into muriate of ammonia
by the common method. (Demachy.) But it is
evident that such a thoughtless proceeding must
be wholly relinquished, since the nitrogen of 100
Ibs. of sal-ammoniac (which contains 26 parts of
nitrogen) is equal to the quantity of nitrogen con-
tained in 1200 Ibs. of the grain of wheat, 1480 Ibs.
of that of barley, or 2755 Ibs. of hay. (Bous-
singault.)
The carbonate of ammonia formed by the putre -
faction of urine, can be fixed or deprived of its
volatility in many ways.
If a field be strewed with gypsum, and then with
putrified urine or the drainings of dunghills, all
the carbonate of ammonia will be converted into
the sulphate which will remain in the soil.
But there are still simpler means of effecting this
purpose ; — gypsum, chloride of calcium, sulphuric
or muriatic acid, and super-phosphate of lime, are
all substances of a very low price, and completely
neutralize the urine, converting its ammonia into
salts which possess no volatility.
If a basin filled with concentrated muriatic acid
is placed in a common necessary, so that its surface
is in free communication with the vapours which rise
o
194 OF MANURE.
from below, it becomes filled after a few days with
crystals of muriate of ammonia. The ammonia, the
presence of which the organs of smell amply testify,
combines with the muriatic acid and loses entirely
its volatility, and thick clouds or fumes of the salt
newly formed hang over the basin. In stables the
same may be seen. The ammonia that escapes in
this manner, is not only entirely lost as far as our
vegetation is concerned, but it works also a slow,
though not less certain destruction of the walls of
the building. For when in contact with the lime
of the mortar, it is converted into nitric acid, which
gradually dissolves the lime. The injury thus done to
a building by the formation of the soluble nitrates,
has received (in Germany) a special name — sal-
peterfrass.
The ammonia emitted from stables and neces-
saries is always in combination with carbonic acid.
Carbonate of ammonia and sulphate of lime
(gypsum) cannot be brought together at common
temperatures, without mutual decomposition. The
ammonia enters into combination with the sul-
phuric acid, and the carbonic acid with the lime,
forming compounds which are not volatile, and,
consequently, destitute of all smell. Now if we
strew the floors of our stables, from time to time,
with common gypsum, they will lose all their of-
fensive smell, and none of the ammonia which
forms can be lost, but will be retained in a condi-
tion serviceable as manure.
TETE USE OF URINE. 195
With the exception of urea, uric acid contains
more nitrogen than any other substance generated
by the living organism ; it is soluble in water, and
can be thus absorbed by the roots of plants, and its
nitrogen assimilated in the form of ammonia, and
of the oxalate, hydrocyanate, or carbonate of am-
monia.
It would be extremely interesting to study the
transformations which uric acid suffers in a living
plant. For the purpose of experiment, the plant
should be made to grow in charcoal powder pre-
viously heated to redness, and then mixed with
pure uric acid. The examination of the juice of the
plant, or of the component parts of the seed or
fruit, would be a means of easily detecting the
differences.
In respect to the quantity of nitrogen contained
in excrements, 100 parts of the urine of a healthy
man are equal to 1300 parts of the fresh dung of
a horse, according to the analyses of Macaire and
Marcet. and to 600 parts of those of a cow. Hence
it is evident that it would be of much importance to
agriculture if none of the human urine were lost.
The powerful effects of urine as a manure are well
known in Flanders, but they are considered invalu-
able by the Chinese, who are the oldest agricultural
people we know. Indeed so much value is attached
to the influence of human excrements by these peo-
ple, that laws of the state forbid that any of them
should be thrown away, and reservoirs are placed
o 2
196 OF MANURE.
in every house, in which they are collected with
the greatest care. No other kind of manure is
used for their corn-fields.
China is the birth-place of the experimental art ;
the incessant striving after experiments has con-
ducted the Chinese a thousand years since to dis-
coveries, which hare been the envy and admiration
of Europeans for centuries, especially in regard to
dyeing and painting, and to the manufactures of
porcelain, silk, and colours for painters. These we
were long unable to imitate, and yet they were dis-
covered by them without the assistance of scientific
principles ; for in the books of the Chinese we find
recipes and directions for use, but never explana-
tions of processes.
Half a century sufficed to Europeans, not only to
equal but to surpass the Chinese in the arts and
manufactures, and this was owing merely to the
application of correct principles deduced from the
study of chemistry. But how infinitely inferior
is the agriculture of Europe to that of China!
The Chinese are the most admirable gardeners and
trainers of plants, for each of which they under-
stand how to prepare and apply the best adapted
manure. The agriculture of their country is the
most perfect in the world ; and there, where the cli-
mate in the most fertile districts differs little from
the European, very little value is attached to the
excrements of animals. With us, thick books are
written, but no experiments instituted ; the quan-
VALUE OF HUMAN EXCREMENTS. 19/
tity of manure consumed by this and that plant,
is expressed in hundredth parts, and yet we know
not what manure is !
If we admit that the liquid and solid excrements
of man amount on an average to 1^ Ibs. daily
(fib. urine and % Ib. faeces), and that both taken
together contain 3 per cent, of nitrogen, then hi
one year they will amount to 547 Ibs., which
contain 16*41 Ibs. of nitrogen, a quantity sufficient
to yield the nitrogen of 800 Ibs. of wheat, rye, oats,
or of 900 Ibs. of barley. (Boussingault.)
This is much more than it is necessary to add to
an acre of land, hi order to obtain, with the assist-
ance of the nitrogen absorbed from the atmo-
sphere, the richest possible crop every year. Every
town and farm might thus supply itself with the
manure, which besides containing the most nitro-
gen,, contains also the most phosphates ; and if an
alternation of the crops were adopted, they would
be most abundant. By using, at the same time,
bones and the lixiviated ashes of wood, the excre-
ments of animals might be completely dispensed
with.
When human excrements are treated in a proper
manner, so as to remove the moisture which they
contain without permitting the escape of ammonia,
they may be put into such a form as will allow
them to be transported, even to great distances.
This is already attempted in many towns, and
the preparation of human excrements for trans-
198 OF MANURE.
portation constitutes not an unimportant branch of
industry. But the manner in which this is done
is the most injudicious which could be conceived.
In Paris, for example, the excrements are preserved
in the houses in open casks, from which they are
collected and placed in deep pits at Montfaucon,
but are not sold until they have attained a certain
degree of dryness by evaporation in the air. But
whilst lying in the receptacles appropriated for
them in the houses, the greatest part of their urea
is converted into carbonate of ammonia; lactate
and phosphate of ammonia are also formed, and
the vegetable matters contained in them putrefy ;
all their sulphates are decomposed, whilst their
sulphur forms sulphuretted hydrogen and hydro-
sulphate of ammonia. The mass when dried by
exposure to the air has lost more than half of the
nitrogen which the excrements originally contained;
for the ammonia escapes into the atmosphere
along with the water which evaporates ; and the
residue now consists principally of phosphate of
lime, with phosphate and lactate of ammonia, and
small quantities of urate of magnesia and fatty
matter. Nevertheless it is still a very powerful
manure, but its value as such would be twice or
four times as great, if the excrements before
being dried were neutralised with a cheap mineral
acid.
In other manufactories of manure, the excre-
ments whilst still soft are mixed with the ashes of
URINE OF ANIMALS. 199
wood, or with earth, both of which substances
contain a large quantity of caustic lime, by means
of which a complete expulsion of all their ammonia
is effected, and they are completely deprived of
smell. But such a residue applied as manure can
act only by the phosphates which it still contains,
for all the ammoniacal salts have been decomposed,
and their ammonia expelled.
The sterile soils of the South American coast are
manured with a substance called guano, consisting
of urate of ammonia, and other ammoniacal salts,
by the use of which a luxuriant vegetation and the
richest crops are obtained. The corn-fields in
China receive no other manure than human excre-
ments. But we cover our fields every year with
the seeds of weeds, which from their nature and
form pass undigested along with the excrements
through animals, without being deprived of their
power of germination, and yet it is considered sur-
prising that where they have once flourished, they
cannot again be expelled by all our endeavours :
we think it very astonishing, while we really sow
them ourselves every year. A famous botanist,
attached to the Dutch embassy to China, could
scarcely' find a single plant on the corn-fields of the
Chinese, except the corn itself*.
The urine of horses contains less nitrogen
and phosphates than that of man. According to
Fourcroy and Vauquelin it contains only five per
* Ingenhouss on the Nutrition of Plants, page 129 (German edition).
200 OF MANURE.
cent, of solid matter, and in that quantity only 0.7
of urea; whilst 100 parts of the urine of man
contain more than four times as much.
The urine of a cow is particularly rich in salts
of potash ; but according to Rouelle and Brande, it
is almost destitute of salts of soda. The urine of
swine contains a large quantity of the phosphate of
magnesia and ammonia; and hence it is that
concretions of this salt are so frequently found in
the urinary bladders of these animals.
It is evident that if we place the solid or
liquid excrements of man, or the liquid excre-
ments of animals, on our land, in equal propor-
tion to the quantity of nitrogen removed from
it in the form of plants, the sum of this element
in the soil must increase every year ; for the
quantity which we thus supply, another portion
is added from the atmosphere. The nitrogen
whichjwe export as corn and cattle, and which is
thus absorbed by large towns, serves only to benefit
other farms, if we do not replace it. A farm
which possesses no pastures, and not fields suffi-
cient for the cultivation of fodder, requires manure
containing nitrogen to be imported from else-
where, if it is desired to produce a full crop. In
large farms, the annual expenditure of nitrogen is
completely replaced by means of the pastures.
The only absolute loss of nitrogen, therefore, is
limited to the quantity which man carries with him
to his grave ; but this at the utmost cannot amount
CONCLUDING REMARKS. 201
to more than 3 Ibs. for every individual, and is being
collected during his whole life. Nor is this quan-
tity lost to plants, for it escapes into the atmosphere
as ammonia during the putrefaction and decay of
the body.
A high degree of culture requires an increased
supply of manure. With the abundance of the
manure the produce in corn and cattle will
augment, but must diminish with its deficiency.
From the preceding remarks it must be evident,
that the greatest value should be attached to the
liquid excrements of man and animals when a
manure is desired which shall supply nitrogen to
the soil. The greatest part of a superabundant
crop, or in other words, the increase of growth
which is in our power, can be obtained exclusively
by their means.
When it is considered that With every pound of
ammonia which evaporates, a loss of 60 Ibs. of
corn is sustained, and that with every pound of
urine a pound of wheat might be produced, the
indifference with which these liquid excrements are
regarded is quite incomprehensible. In most
places, only the solid excrements impregnated with
the liquid are used, and the dunghills containing
them are protected neither from evaporation nor
from rain. The solid excrements contain the
insoluble, the liquid all the soluble phosphates, and
the latter contain likewise all the potash which
202 OF MANURE.
existed as organic salts in the plants consumed by
the animals.
Fresh bones, wool, hair, hoofs, and horn, are
manures containing nitrogen as well as phos-
phates, and are consequently fit to aid the process
of vegetable life.
One hundred parts of dry bones contain from
32 to 33 per cent, of dry gelatine ; now, supposing
this to contain the same quantity of nitrogen as
animal glue, viz. 5*28 per cent., then 100 parts of
bones must be considered as equivalent to 250 parts
of human urine.
Bones may be preserved unchanged for thousands
of years, in dry or even in moist soils, provided the
access of rain is prevented, as is exemplified by the
bones of antediluvian animals found in loam or gyp-
sum, the interior parts being protected by the exte-
rior from the action of water. But they become warm
when reduced to a fine powder, and moistened bones
generate heat and enter into putrefaction ; the
gelatine which they contain is decomposed, and its
nitrogen converted into carbonate of ammonia and
other ammoniacal salts, which are retained in a
great measure by the powder itself. (Bones burnt
till quite white, and recently heated to redness,
absorb 7*5 times their volume of pure ammoniacal
gas.)
Charcoal in a state of powder must be considered
as a very powerful means of promoting the growth
CONCLUDING REMARKS. 203
of plants on heavy soils, and particularly on such
as consist of argillaceous earth.
Ingenhouss proposed dilute sulphuric acid as
a means of increasing the fertility of a soil. Now,
when this acid is sprinkled on calcareous soils,
gypsum (sulphate of lime) is immediately formed,
which of course prevents the necessity of manuring
the soils with this material. 100 parts of concen-
trated sulphuric acid diluted with from 800 to
1000 parts of water, are equivalent to 176 parts of
gypsum.
APPENDIX TO PART I.
GROWTH OF PLANTS WITHOUT MOULD. '
(See Page 61.)
" SOME account of a suspended plant of Ficus Australis,
which was grown for eight months without earth in the stove
of the Botanic Garden at Edinburgh. By Mr. William
Macnab, superintendant of the Garden." (From the 3rd vol.
of the ' Edinburgh Philosophical Journal,' p. 77. Slightly
abridged.)
44 Ficus Australis is a native of New South Wales, and
was introduced into the British gardens in 1789, by the
Right Honourable Sir Joseph Banks. The plant is not
uncommon now in collections in this country, where it has
been usually treated as a greenhouse plant ; and in a good
greenhouse it thrives tolerably well, although it seems
rather more impatient of cold than many of the plants from
the same country.
*' When I came to superintend this garden in 1810, I
found a specimen of it among the greenhouse plants, where
it remained for some time afterwards ; but owing to the bad
construction of the greenhouse here, and the very hardy
way in which J was obliged to treat the plants in that depart-
ment, I did not find the Ficus thrive so well as I had been
accustomed to see it do. I concluded that it required more
heat, and in the spring of 1811 I placed it in the stove,
when it soon began to grow as vigorously as I had ever seen
it do.
APPENDIX. 205
" The stem of the plant was about a foot in height before
any branches set out; on one of the branches, above two
feet from the junction with the stem, a root was put out.
As soon as this had grown about a foot long, I placed a pot
under it. As soon as I found this pot filled with roots, I
determined to try whether if supplied plentifully with water
it would support the whole plant.
" In August 1816, 1 left off watering the original large pot,
and supplied the smaller one very freely with water ; I kept
it in this state for about eight months, till the earth in the
large pot was so completely dry, that I was satisfied the
plant could receive no nourishment from it. The shrub
continued quite as healthy and vigorous as when supplied
with water at the original root. In the spring of 1817, I
took off the large pot in which the original roots were, and
exposed the roots to the full rays of the sun, by gradually
shaking off the dry earth from among them ; this had no ill
effect on the plant, as it still remained perfectly healthy ;
it, however, had the effect of making roots be put out freely
all over the plant, much more so than had hitherto been the
case.
" In the latter end of the summer of 1817, I placed a root
in a third pot, which was put out from a branch about three
feet from the junction with the stem, and on the opposite side
of the plant from that which had supported it for some time
past. As soon as I found this pot filled with fibres, I sup-
plied it freely with water, and kept the other small pot dry,
as I had done before with the original root. I found the
plant still continue equally vigorous as before. In the
spring of 1818, I took away the second pot, which I had
for some time kept dry, and exposed the roots gradually, as
I had formerly done with those in the original pot.
" The third pot, which now alone supported the plant, was
four feet from the lower end of the stem, and very near to the
extremity of the branch, the original roots, and the second
set of roots, both hanging loose in the air. The plant, how-
ever, remained in this state for nearly a year in perfect
206 APPENDIX.
health. In May 1819, I took a very small pot, about two
inches in diameter, and filled it with earth as I had done
the others, and set it on the surface of the earth in the third
pot which now supported the plant. Into this small pot I
introduced a root which came from the same branch, a little
below the one which was in the larger (third) pot. As soon
as the small pot was filled with roots, I supplied it freely
with water, and gave the larger pot none but what might hap-
pen to run through the small one. After remaining in this
state for near two months, I cut the branch off between the
two pots ; I still supplied the small pot only with water, but
occasionally at this time threw a little water over the whole
plant. It continued to look as well as it had done before.
" In July last 1819, 1 examined the small pot (the fourth
used), arid found it completely filled with roots, very little
earth remaining in the pot. By this time the plant appeared
to me to be very tenacious of life, and I determined to try
whether it would live wholly without earth. I accordingly took
the small (fourth) pot off, and gradually worked off what little
earth remained among the roots. I at this time, however,
threw plenty of water over the leaves, generally twice in
the day: this was done about the latter end of July, when
the weather was very warm, but it seemed to have no bad
effects on the Ficus.
" What may appear rather remarkable, is, that though this
Ficus is a plant by no means free in producing fruit in the
usual way of cultivating it, this specimen, quite suspended
without a particle of earth, was loaded with figs during the
months of September, October, and part of November. Two
fruit were produced at the axilla of almost every leaf, and
these were quite as large as I had ever seen on the plant in
the hot-houses of Kew garden. The plant is beginning to
grow or extend, although it has now been suspended for
eight months without a particle of earth, and during that
time we have had very hot weather, and also very coid
weather. Roots have been put out very freely all over the
stem and branches during that time. The plant now
APPENDIX. 207
(February 1819) measures 7-J- feet between the extremity
of the root and the top of the branches, and the stem at the
thickest part is 5|- inches in circumference."
EXPERIMENTS AND OBSERVATIONS ON THE ACTION OF
CHARCOAL FROM WOOD ON VEGETATION. BY EDWARD
LUCAS.
(See page 61.)
" IN a division of a low hothouse in the botanical garden
at Munich, a bed was set apart for young tropical plants,
but instead of being filled with tan, as is usually the case,
it was filled with the powder of charcoal, (a material which
could be easily procured,) the large pieces of charcoal hav-
ing been previously separated by means of a sieve. The
heat was conducted by means of a tube of white iron into a
hollow space in this bed, and distributed a gentle warmth,
sufficient to have caused tan to enter into a state of fermen-
tation. The plants placed in this bed of charcoal quickly
vegetated, and acquired a healthy appearance. Now, as
always is the case in such beds, the roots of many of the
plants penetrated through the holes in the bottom of the
pots, and then spread themselves out ; but these plants
evidently surpassed in vigour and general luxuriance plants
grown in the common way, for example, in tan. Several
of them, of which I shall only specify the beautiful Thun-
bergia alata, and the genus Peireskia, throve quite astonish-
ingly; the blossoms of the former were so rich, that all who
saw it affirmed, they had never before seen such a specimen.
It produced also a number of seeds without any artificial
aid, while in most cases it is necessary to apply the pollen
by the hand. The Peireskia grew so vigorously, that the
P. aculeata produced shoots several ells in length, and the
P. grundifolia acquired leaves of a foot in length. These
facts, as well as the quick germination of the seeds which
had been scattered spontaneously, and the abundant
appearance of young Filices9 naturally attracted my
208 APPENDIX.
attention, and I was gradually led to a series of experi-
ments, the results of which may not be uninteresting ; for,
besides being of practical use in the cultivation of most
plants, they demonstrate also several facts of importance to
physiology. " The first experiment which naturally sug-
gested itself, was to mix a certain proportion of charcoal with
the earth in which different plants grew, and to increase its
quantity according as the advantage of the method was per-
ceived. An addition off of charcoal, for example, to vegeta-
ble mould, appeared to answer excellently for the Gesneria,
and Gloxyma, and also for the tropical Aroidecs with tuberous
roots. The two first soon excited the attention of connois-
seurs, by the great beauty of all their parts and their general
appearance. They surpassed very quickly those cultivated
in the common way, both in the thickness of their stems and
dark colour of their leaves ; their blossoms were beautiful,
and their vegetation lasted much longer than usual, so much
so, that in the middle of November, when other plants of
the same kinds were dead, these were quite fresh and
partly in bloom. Aroideae took root very rapidly, and their
leaves surpassed much in size the leaves of those not so
treated ; the species, which are reared as ornamental plants
on account of the beautiful colouring of their leaves, (I mean,
such as the Caladium bicolor, Pictum, Pcecile, &.C.), were
particularly remarked for the liveliness of their tints; and it
happened here also, that the period of their vegetation was
unusually long. A cactus planted in a mixture of equal
parts of charcoal and earth throve progressively, and attained
double its former size in the space of a few weeks. The
use of the charcoal was very advantageous with several of the
Bromeliacea, and Liliacece, with the Citrus and Begonia also,
and even with the Palmce. The same advantage was found
in the case of almost all those plants for which sand is used,
in order to keep the earth porous, when charcoal was mixed
with the soil instead of sand ; the vegetation was always
rendered stronger and more vigorous.
" At the same time that these experiments were performed
APPENDIX. 209
with mixtures of charcoal with different soils, the charcoal
was also used free from any addition, and in this case the best
results were obtained. Cuts of plants from different genera
took root in it well and quickly ; I mention here only the
Euphorbia fastuosa andfulgens which took root in ten days,
Pandanus utilis in three months, P. amaryllifolius, Chamce-
dorea elatior in four weeks, Pipernigrum, Begonia, Ficus,
Cecropia, Chiococca, Buddleja, Hakea, PhyUanthus, Capparis,
Laurus, Stifftia, Jacquinia, Mimosa, Cactus, in from eight to
ten days, and several others amounting to forty species, in-
cluding Ilex, and many others. Leaves, and pieces of leaves,
and even pedunculi, or petioles, took root and in part budded
in pure charcoal. Amongst others we may mention the
foliola of several of the Cycadece as having taken root, as also
did parts of the leaves of the Begonia Telsairice, andJacaranda
brasiliensis ; leaves of the Euphorbia fastuosa, Oxalis Barri-
lieri, Ficus, Cyclamen, Polyanihes, Mesembrianthemum ; also,
the delicate leaves of the Lophospermum and Martynia,
pieces of a leaf of the Agave Americana ; tufts of Pinus, &c. ;
and all without the aid of a previously formed bud.
" Pure charcoal acts excellently as a means of curing
unhealthy plants. A Dorianthes excelsa, for example, which
had been drooping for three years, was rendered completely
healthy in a very short time by this means. An orange-tree
which had the very common disease in which the leaves
become yellow, acquired within four weeks its healthy green
colour, when the upper surface of the earth was removed from
the pot in which it was contained, and a ring of charcoal of
an inch in thickness strewed in its place around the peri-
phery of the pot. The same was the case with the Gardenia.
" I should be led too far were I to state all the results of the
experiments which I have made with charcoal. The object
of this paper is merely to show the general effect exercised
by this substance on vegetation, but the reader who takes
particular interest in the subject, will find more extensive
observations in the ' Allgemeine deutsche Gartenzeitung '
of Otto and Dietrich in Berlin.
210 APPENDIX.
" The charcoal employed in these experiments was the
dust-like powder of charcoal from firs and pines, such as is
used in the forges of blacksmiths, and may be easily pro-
cured in any quantity. It was found to have most effect
when allowed to lie during the winter exposed to the action
of the air. In order to ascertain the effects of different
kinds of charcoal, experiments were also made upon that
obtained from the hard woods and peat, and also upon
animal charcoal, although I foresaw the probability that
none of them would answer so well as that of pinewood,
both on account of its porosity and the ease with which it
is decomposed.
'* It is superfluous to remark, that in treating plants in the
manner here described, they must be plentifully supplied
with water, since the air having such free access penetrates
and dries the roots, so that unless this precaution is taken,
the failure of all such experiments is unavoidable.
" The action of charcoal consists primarily in its preserving
the parts of the plants with which it is in contact ; whether
they be roots, branches, leaves, or pieces of leaves, un-
changed in their vital power for a long space of time, so
that the plant obtains time to develop the organs which
are necessary for its further support and propagation.
There can scarcely be a doubt also that the charcoal under-
goes decomposition ; for after being used five to six years
it becomes a coaly earth ; and if this is the case, it must
yield carbon, or carbonic oxide, abundantly to the plants
growing in it, and thus afford the principal substance ne-
cessary for the nutrition of vegetables. In what other manner
indeed can we explain the deep green colour and great luxu-
riance of the leaves and every part of the plants, which can
be obtained in no other kind of soil, according to the opinion
of men well qualified to judge? It exercises likewise a
favourable influence by decomposing and absorbing the
matters absorbed [query, excreted] by the roots, so as to keep
the soil free from the putrefying substances which are often
the cause of the death of the spongiolce. Its porosity as well as
APPENDIX. 211
the power which it possesses, of absorbing water with rapidity,
and, after its saturation, of allowing all other water to sink
through it, are causes also of its favourable effects. These
experiments show what a close affinity the component parts
of charcoal have to all plants, for every experiment was
crowned with success, although plants belonging to a great
many different families were subjected to trial/' (Buchner's
Repertorium,\\. Reihe, xix. Ed. S. 38.)
ON THE ROTATION OF CROPS AT BINGEN ON THE RHINE.
(See Page 172.)
The alternation of crops with esparsette and lucern is now
universally adopted in Bingen and its vicinity as well as in
the Palatinate ; the fields in these districts receive manure
only once every nine years. In the first year after the
land has been manured, turnips are sown upon it, in the next
following years barley, with esparsette or lucern ; in the
seventh year potatoes, in the eighth wheat, in the ninth
barley ; on the tenth year it is manured, and then the same
rotation again takes place.
ON A MODE OF MANURING VINES.
The observations contained in the following pages should
be extensively known, because they furnish a remarkable
proof of the principles which have been stated in the preced-
ing part of the work, both as to the manner in which manure
acts, and on the origin of the carbon and nitrogen of plants.
They prove that a vineyard may be retained in fertility
without the application of animal matters, when the leaves
and branches pruned from the vines are cut into small
pieces and used as manure. According to the first of the
following statements, both of which merit complete con-
fidence, the perfect fruitfulness of a vineyard has been
P 2
212 APPENDIX.
maintained in this manner for eight years, and 'according
to the second statement for ten years.
Now, during this long period, no carbon was conveyed to
the soil, for that contained in the pruned branches was the
produce of the plant itself, so that the vines were placed
exactly in the same condition as trees in a forest which
received no manure. Under ordinary circumstances a
manure containing potash must be used, otherwise the
fertility of the soil will decrease. This is done in all wine-
countries, so that alkalies to a very considerable amount
must be extracted from the soil.
When, however, the method of manuring now to be
described is adopted, the quantity of alkalies exported in the
wine does not exceed that which the progressive disinte-
gration of the soil every year renders capable of being
absorbed by the plants. On the Rhine 1 litre of wine is cal-
culated as the yearly produce of a square metre of land (10'8
square feet English). Now if we suppose that the wine is
three-fourths saturated with cream of tartar, a proportion
much above the truth, then we remove from every square
metre of land with the wine only 1*8 gramme of potash.
1000 grammes (1 litre) of champagne yield only 1'54, and
the same quantity of Wachenheimer 1*72 of a residue which
after being heated to redness is found to consist of car-
bonates.
One vine-stock, on an average, grows on every square
metre of land, and 1000 parts of the pruned branches
contain 56 to 60 parts of carbonate, or 38 to 40 parts of pure
potash. Hence it is evident that 45 grammes, or 1 ounce, of
these branches contain as much potash as 1000 grammes (1
litre) of wine. But from ten to twenty times this quantity of
branches are yearly taken from the above extent of surface.
In the vicinity of Johannisberg, Rudesheim, and Budes-
heim, new vines are not planted after the rooting out of the
old stocks, until the land has lain for five or six years in
barley and esparsette or lucern ; in the sixth year the
young stocks planted, but not manured till the ninth.
APPENDIX. 213
ON THE MANURING OF THE SOIL IN VINEYARDS.*
" In reference to an article in your paper, No. 7, 1838, and
No. 29, 1839, 1 cannot omit the opportunity of again calling
the public attention to the fact that nothing more is neces-
sary for the manure of a vineyard, than the branches which
are cut from the vines themselves.
" My vineyard has been manured in this way for eight
years, without receiving any other kind of manure, and yet
more beautiful and richly laden vines could scarcely be
pointed out. I formerly followed the method usually prac-
tised in this district, and was obliged in consequence to
purchase manure to a large amount. This is now entirely
saved, and my land is in excellent condition.
66 When I see the fatiguing labour used in the manuring
of vineyards — horses and men toiling up the mountains with
unnecessary materials — I feel inclined to say to all, come to
my vineyard and see how a bountiful Creator has provided
that vines shall manure themselves, like the trees in a forest,
and even better than they ! The foliage falls from trees in
a forest, only when they are withered, and they lie for years
before they decay ; but the branches are pruned from the
vine in the end of July or beginning of August whilst still
fresh and moist. If they are then cut into small pieces and
mixed with the earth, they undergo putrefaction so com-
pletely, that, as 1 have learned by experience, at the end
of four weeks not the smallest trace of them can be
found."
* Slightly abridged from an article by M. Krebs of Seeheim in the
" Zeitschrift fur die landwirthschaftlichen Vereine des Grosherzogthums
Hessen." No. 28, July 9, 1840.
214 APPENDIX.
" Remarks of the editor. — We find the following notices
of the same fact in Henderson's c History of Wines of the
old and new time f —
" ' The best manure for vines is the branches pruned from
the vines themselves, cut into small pieces, and immediately
mixed with the soil.''
" These branches were used as manure long since in the
Bergstrasse. M. Frauenfelder says : *
" * I remember that twenty years ago, a man called Peter
Mliller had a vineyard here which he manured with the
branches pruned from the vines, and- continued this practice
for thirty years. His way of applying them was to hoe them
into the soil after having cut them into small pieces.
46 ' His vineyard was always in a thriving condition; so
much so indeed, that the peasants here speak of it to this
day wondering that old Miiller had so good a vineyard, and
yet used no manure/
" Lastly, Wilhelm Ruf of Schriesheim writes :
" < For the last ten years I have been unable to place dung
on my vineyard, because I am poor and can buy none. But
I was very unwilling to allow my vines to decay, as they are
my only source of support in my old age ; and I often walked
very anxiously amongst them, without knowing what I
should do. At last my necessities became greater, which
made me more attentive, so that I remarked that the grass
was longer on some spots where the branches of the vine
fell than on those on which there were none. So I thought
upon the matter, and then said to myself: If these branches
can make the grass large, strong, and green, they must also
be able to make my plants grow better, and become strong
and green. I dug therefore my vineyard as deep as if I would
put dung into it, and cut the branches into pieces, placing
* Badisches landwirthschaftliches Wochenblatt, v.. 1834. S. 52 and 79.
APPENDIX. 215
them in the holes and covering them with earth. In a year
I had the very great satisfaction to see my barren vineyard
become quite beautiful. This plan I continued every year,
and now my vines grow splendidly, and remain the whole
summer green, even in the greatest heat.
" All my neighbours wonder very much how my vineyard
is so rich, and that I obtain so many grapes from it, and yet
they all know that I have put no dung upon it for ten
years."
PART II.
OF THE CHEMICAL PROCESSES OF FERMENTATION, DECAY'
AND PUTREFACTION.
CHEMICAL TRANSFORMATIONS.
WOODY fibre, sugar, gum, and all such organic
compounds, suffer certain changes when in contact
with other bodies, that is, they suffer decomposition.
There are two distinct modes in which these
decompositions take place in organic chemistry.
When a substance composed of two compound
bodies, crystallised oxalic acid for example, is
brought in contact with concentrated sulphuric
acid, a complete decomposition is effected upon the
application of a gentle heat. Now crystallised
oxalic acid is a combination of water with the anhy-
drous acid ; but concentrated sulphuric acid pos-
sesses a much greater affinity for water than oxalic
acid, so that it attracts all the water of crystallization
from that substance. In consequence of this abstrac-
tion of the water, anhydrous oxalic acid is set free ;
but as this acid cannot exist in a free state, a divi-
sion of its constituents necessarily ensues, by which
carbonic acid and carbonic oxide are produced, and
evolved in the gaseous form in equal volumes.
In this example, the decomposition is the con-
sequence of the removal of two constituents (the
218 CHEMICAL TRANSFORMATIONS.
elements of water), which unite with the sulphuric
acid,, and its cause is the superior affinity of the
acting body (the sulphuric acid) for water. In
consequence of the removal of the component
parts of water, the remaining elements enter into
a new form ; in place of oxalic acid, we have its
elements in the form of carbonic acid and carbonic
oxide.
This form of decomposition, in which the change
is effected by the agency of a body which unites
with one or more of the constituents of a com-
pound, is quite analogous to the decomposition of
inorganic substances. When we bring sulphuric
acid and nitrate of potash together, nitric acid is
separated in consequence of the affinity of sulphuric
acid for potash ; in consequence, therefore, of the
formation of a new compound (sulphate of potash).
In the second form of these decompositions,
the chemical affinity of the acting body causes
the component parts of the body which is decom-
posed to combine so as to form new compounds,
of which either both, or only one, combine with the
acting body. Let us take dry wood, for example, and
moisten it with sulphuric acid ; after a short time
the wood is carbonised, while the sulphuric acid
remains unchanged, with the exception of its being
united with more water than it possessed before.
Now this water did not exist as such in the wood,
although its elements, oxygen and hydrogen, were
present ; but by the chemical attraction of sul-
EXAMPLES. 219
phuric acid for water, they were in a certain
measure compelled to unite in this form ; and in
consequence of this, the carbon of wood was
separated as charcoal.
Hydrocyanic acid, and mater., in contact with
hydrochloric acid, are mutually decomposed. The
nitrogen of the hydrocyanic acid, and a certain
quantity of the hydrogen of the water, unite to-
gether and form ammonia ; whilst the carbon and
hydrogen of the hydrocyanic acid combine with the
oxygen of the water, and form formic acid. The
ammonia combines with the muriatic acid. Here
the contact of muriatic acid with water and hydro-
cyanic acid causes a disturbance in the attraction
of the elements of both compounds, in consequence
of which they arrange themselves into new com-
binations, one of which — ammonia — possesses the
power of uniting with the acting body.
Inorganic chemistry can present instances analo-
gous to this class of decomposition also ; but there
are forms of organic chemical decomposition of a
very different kind, in which none of the compo-
nent parts of the matter which suffers decomposition
enters into combination with the body which de-
termines the decomposition. In cases of this kind
a disturbance is produced in the mutual attraction
of the elements of a compound, and they in conse-
quence arrange themselves into one or several new
combinations, which are incapable of suffering
further change under the same conditions.
220 CHEMICAL TRANSFORMATIONS.
When, by means of the chemical affinity of a
second body, by the influence of heat, or through
any other causes, the composition of an organic
compound is made to undergo such a change, that
its elements form two or more new compounds, this
manner of decomposition is called a chemical
transformation or metamorphosis. It is an essen-
tial character of chemical transformations, that
none of the elements of the body decomposed are
singly set at liberty.
The changes, which are designated by the terms
fermentation, decay, and putrefaction, are chemical
transformations effected by an agency which has
hitherto escaped attention, but the existence of
which will be proved in the following pages.
ON THE CAUSES WHICH EFFECT FERMENTATION,
DECAY,* AND PUTREFACTION.
ATTENTION has been recently directed to the
fact, that a body in the act of combination or de-
composition exercises an influence upon any other
body with which it may be in contact. Platinum,
for example, does not decompose nitric acid ; it
may be boiled with this acid without being oxidised
* An essential distinction is drawn in the following part of the work,
between decay and putrefaction (Verwesung und F'dulniss\ and they are
shown to depend on different causes ; but as the word decay is not gene-
rally applied to a distinct species of decomposition, and does not indi-
cate its true nature, I shall in future, at the suggestion of the author,
employ the term eremacausis, the meaning of which has been already ex-
plained.—TRANS.
THEIR CAUSE. 221
by it, even when in a state of such fine division,
that it no longer reflects light (black spongy
platinum). But an alloy of silver and platinum
dissolves with great ease in nitric acid ; the oxida-
tion which the silver suffers, causes the platinum to
submit to the same change ; or, in other words,
the latter body from its contact with the oxidizing
silver, acquires the property of decomposing nitric
acid.
Copper does not decompose water, even when
boiled in dilute sulphuric acid, but an alloy of
copper, zinc, and nickel, dissolves easily in this acid
with evolution of hydrogen gas.
Tin decomposes nitric acid with great facility,
but water with difficulty ; and yet, when tin is dis-
solved in nitric acid, hydrogen is evolved at the
same time, from a decomposition of the water con-
tained in the acid, and ammonia is formed in
addition to oxide of tin.
In the examples here given, the only combina-
tion or decomposition which can be explained by
chemical affinity is the last. In the other cases,
electrical action ought to have retarded or prevented
the oxidation of the platinum or copper while they
were in contact with silver or zinc, but, as experience
shows, the influence of the opposite electrical con-
ditions is more than counterbalanced by chemical
actions.
The same phenomena are seen in a less dubious
form in compounds, the elements of which are held
222 CHEMICAL TRANSFORMATIONS.
together only by a weak affinity. It is well known
that there are chemical compounds of so unstable a
nature, that changes in temperature and electrical
condition, or even simple mechanical friction, or
contact with bodies of apparently totally indifferent
natures, cause such a disturbance in the attraction
of their constituents, that the latter enter into new
forms, without any one of them combining with the
acting body. These compounds appear to stand
but just within the limits of chemical combination,
and agents exercise a powerful influence on them,
which are completely devoid of action on com-
pounds of a stronger affinity. Thus, by a slight
increase of temperature, the elements of hypochlo-
rous acid separate from one another with evolution
of heat and light ; chloride of nitrogen explodes by
contact with many bodies, which combine neither
with chlorine nor nitrogen at common tempera-
tures; and the contact of any solid substance is
sufficient to cause the explosion of iodide of nitro-
gen, or fulminating silver.
It has never been supposed that the causes
of the decomposition of these bodies should be
ascribed to a peculiar power, different from that
which regulates chemical affinity, — a power which
mere contact with the down of a feather is
sufficient to set in activity, and which, once in
action, gives rise to the decomposition. These
substances have always been viewed as chemical
combinations of a very unstable nature, in which
THEIR CAUSE. 223
the component parts are in a state of such ten-
sion, that the least disturbance overcomes their
chemical affinity. They exist only by the vis
inertia, and any shock or movement is sufficient
to destroy the attraction of their component parts,
and consequently their existence in their definite
form.
Peroxide of hydrogen belongs to this class of
bodies ; it is decomposed by all substances capable
of attracting oxygen from it, and even by contact
with many bodies, such as platinum or silver, which
do not enter into combination with any of its con-
stituents. In this respect, its decomposition depends
evidently upon the same causes which effect that
of iodide of nitrogen, or fulminating silver. Yet it
is singular that the cause of the sudden separation
of the component parts of peroxide of hydrogen
has been viewed as different from those of common
decomposition, and has been ascribed to a new
power termed the catalytic force. Now, it has not
been considered, that the presence of the platinum
and silver serves here only to accelerate the decom-
position ; for without the contact of these metals,
the peroxide of hydrogen decomposes spontane-
ously, although very slowly. The sudden separa-
tion of the constituents of peroxide of hydrogen
differs from the decomposition of gaseous hypochlo-
rous acid, or solid iodide of nitrogen, only in so
far as the decomposition takes place in a liquid.
A remarkable action of peroxide of hydrogen has
224 CHEMICAL TRANSFORMATIONS.
attracted much attention, because it differs from
ordinary chemical phenomena. This is the reduc-
tion which certain oxides suffer by contact with this
substance, on the instant at which the oxygen sepa-
rates from the water. The oxides thus easily re-
duced, are those of which the whole, or part at
least, of their oxygen is retained merely by a feeble
affinity, such as the oxides of silver and of gold,
and peroxide of lead.
Now, other oxides which are very stable in com-
position, effect the decomposition of peroxide of
hydrogen, without experiencing the smallest change ;
but when oxide of silver is employed to effect the
decomposition, all the oxygen of the silver is carried
away with that evolved from the peroxide of hydro-
gen, and as a result of the decomposition, water
and metallic silver remain. When peroxide of
lead is used for the same purpose, half its oxygen
escapes as a gas. Peroxide of manganese may in
the same manner be reduced to the protoxide, and
oxygen set at liberty, if an acid is at the same
time present, which will exercise an affinity for
the protoxide and convert it into a soluble salt.
If, for example, we add to peroxide of hydro-
gen sulphuric acid, and then peroxide of man-
ganese in the state of fine powder, much more
oxygen is evolved than the compound of oxygen
and hydrogen could yield; and if we examine
the solution which remains, we find a salt of
the protoxide of manganese, so that half of the
THEIR CAUSE.
oxygen has been evolved from the peroxide of that
metal.
A similar phenomenon occurs, when carbonate
of silver is treated with several organic acids. Pyr-
uvic acid, for example, combines readily with pure
oxide of silver, and forms a salt of sparing solubility
in water. But when this acid is brought in contact
with carbonate of silver, the oxygen of part of the
oxide escapes with the carbonic acid, and metallic
silver remains in the state of a black powder.
(Berzelius.)
Now no other explanation of these phenomena
can be given, than that a body in the act of combina-
tion or decomposition enables another body, with
which it is in contact, to enter into the same state.
It is evident that the active state of the atoms of
one body has an influence upon the atoms of a
body in contact with it; and if these atoms are
capable of the same change as the former, they
likewise undergo that change ; and combinations
and decompositions are the consequence. But
when the atoms of the second body are not capable
of such an action, any further disposition to change
ceases from the moment at which the atoms of the
first body assume the state of rest, that is, when
the changes or transformations of this body are
quite completed.
This influence exerted by one compound upon
the other, is exactly similar to that which a body
in the act of combustion exercises upon a combus-
Q
226 CHEMICAL TRANSFORMATIONS.
tible body in its vicinity ; with this difference only,
that the causes which determine the participation
and duration of these conditions are different. For
the cause, in the case of the combustible body, is heat,
which is generated every moment anew ; whilst in
the phenomena of decomposition and combination,
which we are considering at present, the cause is a
body in the state of chemical action, which exerts
the decomposing influence only so long as this
action continues.
Numerous facts show that motion alone exercises
a considerable influence on chemical forces. Thus,
the power of cohesion does not act in many saline
solutions, even when they are fully saturated with
salts, if they are permitted to cool whilst at rest.
In such a case, the salt dissolved in a liquid does
not crystallise, but when a grain of sand is thrown
into the solution, or when it receives the slightest
movement, the whole liquid becomes suddenly
solid while heat is evolved. The same phenomenon
happens with water, for this liquid may be cooled
much under 32° (0° C.), if kept completely undis-
turbed, but solidifies in a moment when put in
motion.
The atoms of a body must in fact be set in mo-
tion before they can overcome the vi$ inertice so
as to arrange themselves into certain forms. A
dilute solution of a salt of potash mixed with tar-
taric acid yields no precipitate whilst at rest ; but
if motion is communicated to the solution by agi-
THEIR CAUSE. 227
tating it briskly, solid crystals of cream of tartar
are immediately deposited. A solution of a salt of
magnesia also, which is not rendered turbid by
the addition of phosphate of ammonia, deposits the
phosphate of magnesia and ammonia on those parts
of the vessel touched with the rod employed in
stirring.
In the processes of combination and decomposition
under consideration, motion, by overcoming the vis
inertia, gives rise immediately to another arrange-
ment of the atoms of a body, that is, to the produc-
tion of a compound which did not before exist in
it. Of course these atoms must previously possess
the power of arranging themselves in a certain
order, otherwise both friction and motion would be
without the smallest influence.
The simple permanence in position of the atoms
of a body, is the reason that so many compounds
appear to present themselves, in conditions, and
with properties, different from those which they
possess, when they obey the natural attractions of
their atoms. Thus sugar and glass, when melted
and cooled rapidly, are transparent, of a conchoidal
fracture, and elastic and flexible to a certain degree.
But the former becomes dull and opaque on keep-
ing, and exhibits crystalline faces by cleavage,
which belong to crystallised sugar. Glass assumes
also the same condition, when kept soft by heat for
a long period ; it becomes white, opaque, and so
hard as to strike fire with steel. Now, in both
Q2
228 CHEMICAL TRANSFORMATIONS.
these bodies, the compound molecules evidently
have different positions in the two forms. In the
first form their attraction did not act in the direc-
tion in which their power of cohesion was strongest.
It is known also, that when sulphur is melted and
cooled rapidly by throwing it into cold water, it
remains transparent, elastic, and so soft that it may
be drawn out into long threads ; but that after a few
hours or days, it becomes again hard and crystalline.
The remarkable fact here is, that the amorphous
sugar or sulphur returns again into the crystalline
condition, without any assistance from an exterior
cause ; a fact which shows that their molecules
have assumed another position, and that they
possess, therefore, a certain degree of mobility,
even in the condition of a solid. A very rapid
transposition or transformation of this kind is seen
in arragonite, a mineral which possesses exactly
the same composition as calcareous spar, but of
which the hardness and different crystalline form
prove that its molecules are arranged in a different
manner. When a crystal of arragonite is heated,
an interior motion of its molecules is caused by the
expansion ; the permanence of their arrangement
is destroyed; and the crystal splinters with much
violence, and falls into a heap of small crystals of
calcareous spar.
It is impossible for us to be deceived regarding
the causes of these changes. They are owing to a
disturbance of the state of equilibrium, in conse-
FERMENTATION AND DECAY. 229
quence of which, the particles of the body put in
motion obey other affinities or their own natural
attractions.
But if it is true, as we have just shown it to be,
that mechanical motion is sufficient to cause a
change of condition in many bodies, it cannot be
doubted that a body in the act of combination or
decomposition is capable of imparting the same
condition of motion or activity in which its atoms
are to certain other bodies : or in other words, to
enable other bodies with which it is in contact to
enter into combinations, or suifer decompositions.
The reality of this influence has been already
sufficiently proved by the facts derived from in-
organic chemistry, but it is of much more frequent
occurrence in the relations of organic matters, and
causes very striking and wonderful phenomena.
By the terms fermentation, putrefaction, and
eremacausis, are meant those changes in form and
properties which compound organic substances
undergo when separated from the organism, and
exposed to the influence of water and a certain
temperature. Fermentation and putrefaction are
examples of that kind of decomposition which we
have named transformations ; the elements of the
bodies capable of undergoing these changes arrange
themselves into new combinations, in which the
constituents of water generally take a part.
Eremacausis (or decay) differs from fermentation
and putrefaction, inasmuch as it cannot take place
230 CHEMICAL TRANSFORMATIONS
without the access of air, the oxygen of which is
absorbed by the decaying bodies. Hence it is
a process of slow combustion, in which heat is
uniformly evolved, and occasionally even light. In
the processes of decomposition, termed fermenta-
tion and putrefaction, gaseous products are very
frequently formed, which are either inodorous, or
possess a very offensive smell.
The transformations of those matters which
evolve gaseous products without odour, are now,
by pretty general consent, designated by the term
fermentation ; whilst to the spontaneous decompo-
sition of bodies which emit gases of a disagreeable
smell, the term putrefaction is applied. But the
smell is of course no distinctive character of the
nature of the decomposition, for both fermentation
and putrefaction are processes of decomposition of
a similar kind, the one of substances destitute of
nitrogen, the other of substances which contain it.
It has also been customary to distinguish from
fermentation and putrefaction a particular class of
transformations, viz., those in which conversions and
transpositions are effected without the evolution of
gaseous products. But the conditions under which
the products of the decomposition present them-
selves are purely accidental ; there is therefore no
reason for the distinction just mentioned.
OF ORGANIC COMPOUNDS. 231
-X
FERMENTATION AND PUTREFACTION.
Several bodies appear to enter spontaneously into
the states of fermentation and putrefaction,, parti-
cularly such as contain nitrogen or azotised sub-
stances. Now, it is very remarkable, that very
small quantities of these substances, in a state of
fermentation or putrefaction, possess the power of
causing unlimited quantities of similar matters to
pass into the same state. Thus, a small quantity of
the juice of grapes in the act of fermentation,
added to a large quantity of the same fluid, which
does not ferment, induces the state of fermentation
in the whole mass. So likewise the most minute
portion of milk, paste, juice of the beet-root, flesh,
or blood, in the state of putrefaction, causes fresh
milk, paste, juice of the beet-root, flesh, or blood,
to pass into the same condition when in contact
with them.
These changes evidently differ from the class
of common decompositions which are effected by
chemical affinity ; they are chemical actions, con-
versions, or decompositions, excited by contact
with bodies already in the same condition. In order
to form a clear idea of these processes, analogous
and less complicated phenomena must previously
be studied.
The compound nature of the molecules of an
organic body, and the phenomena presented by
them when in relation with other matters, point out
the true cause of these transformations. Evidence
232 CHEMICAL TRANSFORMATIONS
is afforded even by simple bodies, that in the forma-
tion of combinations, the force with which the
combining elements adhere to one another is
inversely proportional to the number of simple
atoms in the compound molecule. Thus, protoxide
af manganese by absorption of oxygen is converted
into the sesquioxide, the peroxide, and manganic
and hypermanganic acids, the number of atoms of
oxygen being augmented by 1, by 1, by 2, and by
5* But all the oxygen contained in these com-
pounds, beyond that which belongs to the protoxide,
is bound to the manganese by a much more feeble
affinity ; a red heat causes an evolution of oxygen
from the peroxide, and the manganic and hyper-
manganic acids cannot be separated from their
bases without undergoing immediate decomposition.
There are many facts which prove, that the most
simple inorganic compounds are also the most
stable, and undergo decomposition with the greatest
difficulty, whilst those which are of a complex com-
position yield easily to changes and decompositions.
The cause of this evidently is, that in proportion
to the number of atoms which enter into a com-
pound, the directions in which their attractions
act will be more numerous.
Whatever ideas we may entertain regarding mat-
ter in general, the existence of chemical proportions
removes every doubt respecting the presence of
certain limited groups or masses of matter which
we have not the power of dividing. The particles
of matter called equivalents in chemistry are not
OF ORGANIC COMPOUNDS. 233
infinitely small,, for they possess a weight, and are
capable of arranging themselves in the most various
ways, and of thus forming innumerable compound
atoms. The properties of these compound atoms
differ in organic nature, not only according to the
form, but also in many instances according to the
direction and place, which the simple atoms take
in the compound molecules.
When we compare the composition of organic
compounds with inorganic, we are quite amazed at
the existence of combinations, in one single mole-
cule of which, ninety or several hundred atoms or
equivalents are united. Thus, the compound atom
of an organic acid of very simple composition,
acetic acid for example, contains twelve equivalents
of simple elements ; one atom of kinovic acid con-
tains 33, 1 of sugar 36, 1 of amygdalin 90, and 1
of stearic acid 138 equivalents. The component
parts of animal bodies are infinitely more complex
even than these.
Inorganic compounds differ from organic in as
great a degree in their other characters as in their
simplicity of constitution. Thus, the decomposition
of a compound atom of sulphate of potash is
aided by numerous causes, such as the power of
cohesion, or the capability of its constituents to
form solid, insoluble, or at certain temperatures
volatile compounds with the body brought into con-
tact with it, and nevertheless a vast number of other
substances produce in it not the slightest change-
234 CHEMICAL TRANSFORMATIONS
Now, in the decomposition of a complex organic
atom, there is nothing similar to this.
The empirical formula of sulphate of potash is
SKO4. It contains only 1 eq. of sulphur, and
1 eq. of potassium. We may suppose the oxygen
to be differently distributed in the compound, and
by a decomposition we may remove a part or all
of it, or replace one of the constituents of the
compound by another substance. But we cannot
produce a different arrangement of the atoms,
because they are already disposed in the simplest
form in which it is possible for them to combine.
Now, let us compare the composition of sugar of
grapes with the above: here 12eq. of carbon, 12
eq. of hydrogen, and 12 eq. of oxygen, are united
together, and we know that they are capable of
combining with each other in the most various
ways. From the formula of sugar, we might
consider it either as a hydrate of carbon, wood,
starch, or sugar of milk, or further, as a compound
of ether with alcohol or of formic acid with sachul-
min.* Indeed we may calculate almost all the
known organic compounds containing no nitrogen
from sugar, by simply adding the elements of water,
or by replacing any one of its elementary consti-
tuents by a different substance. The elements
necessary to form these compounds are therefore
contained in the sugar, and they must also possess
* The black precipitate obtained by the action of hydrochloric acid on
sugar.
OF ORGANIC COMPOUNDS. 235
the power of forming numerous combinations
amongst themselves by their mutual attractions.
Now, when we examine what changes sugar
undergoes when brought into contact with other
bodies which exercise a marked influence upon it,
we find, that these changes are not confined to any
narrow limits, like those of inorganic bodies, but
are in fact unlimited.
The elements of sugar yield to every attraction,
and to each in a peculiar manner. In inorganic
compounds, an acid acts upon a particular consti-
tuent of the body, which it decomposes, by virtue of
its affinity for that constituent, and never resigns
its proper chemical character, in whatever form it
may be applied. But when it acts upon sugar, and
induces great changes in it, it does this, not by its
superior affinity for a base existing in the sugar,
but by disturbing the equilibrium in the mutual
attraction of the elements of the sugar amongst
themselves. Muriatic and sulphuric acids, which
differ so much from one another both in characters
and composition, act in the same manner upon
sugar. But the action of both varies according to
the state in which they are ; thus they act in one
way when dilute, in another when concentrated, and
even differences in their temperature cause a change
in their action. Thus sulphuric acid of a moderate
degree of concentration converts sugar into a black
carbonaceous matter, forming at the same time
acetic and formic acids. But when the acid is more
236 CHEMICAL TRANSFORMATIONS
diluted, the sugar is converted into two brown sub-
stances, both of them containing carbon and the
elements of water. Again, when sugar is subjected
to the action of alkalies, a whole series of different
new products are obtained, while oxidizing agents,
such as nitric acid, produce from it carbonic acid,
acetic acid, oxalic acid, formic acid, and many other
products which have not yet been examined.
If from the facts here stated we estimate the
power with which the elements of sugar are united
together, and judge of the force of their attraction
by the resistance which they offer to the action of
bodies brought into contact with them, we must
regard the atom of sugar as belonging to that class
of compound atoms, which exist only by the vis
inertice of their elements. Its elements seem
merely to retain passively the position and condi-
tion in which they had been placed, for we do not
observe that they resist a change of this condition
by their own mutual attraction, as is the case with
sulphate of potash.
Now it is only such combinations as sugar, com-
binations therefore which possess a very complex
molecule, which are capable of undergoing the
decompositions named fermentation and putrefac-
tion.
We have seen that metals acquire a power which
they do not of themselves possess, namely, that of
decomposing water and nitric acid, by simple contact
with other metals in the act of chemical combination.
OF ORGANIC COMPOUNDS. 237
We have also seen, that peroxide of hydrogen and
the persulphuret of the same element, in the act of
decomposition, cause other compounds of a similar
kind, but of which the elements are much more
strongly combined, to undergo the same decompo-
sition, although they exert no chemical affinity or
attraction for them or their constituents. The
cause which produces these phenomena will be
also recognised, by attentive observation, in those
matters which excite fermentation or putrefaction.
All bodies in the act of combination or decomposi-
tion have the property of inducing those processes ;
or, in other words, of causing a disturbance of the
statical equilibrium in the attractions of the elements
of complex organic molecules, in consequence of
which those elements group themselves anew, ac-
cording to their special affinities.
The proofs of the existence of this cause of
action can be easily produced ; they are found in
the characters of the bodies which effect fermenta-
tion and putrefaction, and in the regularity with
which the distribution of the elements takes place
in the subsequent transformations. This regularity
depends exclusively on the unequal affinity which
they possess for each other in an isolated condition.
The action of water on wood, charcoal, and cyano-
gen, the simplest of the compounds of nitrogen,
suffices to illustrate the whole of the transforma-
tions of organic bodies ; of those in which nitrogen
is a constituent, and of those in which it is absent.
238 CHEMICAL TRANSFORMATIONS
ON THE TRANSFORMATION OF BODIES WHICH
DO NOT CONTAIN NITROGEN AS A CONSTI-
TUENT.
WHEN oxygen and hydrogen combined in equal
equivalents, as in steam, are conducted over char-
coal, heated to the temperature at which it pos-
sesses the power to enter into combination with
one of these elements, a decomposition of the steam
ensues. An oxide of carbon (either carbonic
oxide or carbonic acid) is under all circumstances
formed, while the hydrogen of the water is liberated,
or, if the temperature be sufficient, unites with the
carbon forming carburetted hydrogen. Accord-
ingly, the carbon is shared between the elements
of the water, the oxygen and hydrogen. Now a
participation of this kind, but even more complete,
is observed in every transformation, whatever be
the nature of the causes by which it is effected.
Acetic and meconic acids suffer a true transfor-
mation under the influence of heat, that is, their
component elements are disunited, and form new
compounds without any of them being singly dis-
engaged. Acetic acid is converted into acetone
and carbonic acid (04 H3 O3 = C3 H3 O + CO2),
and meconic acid into carbonic acid and komenic
acid ; whilst by the influence of a higher tempera-
ture, the latter is further decomposed into pyro-
meconic acid and carbonic acid.
Now in these cases the carbon of the bodies de-
OF BODIES DESTITUTE OF NITROGEN. 239
composed is shared between the oxygen and hydro-
gen ; part of it unites with the oxygen and forms
carbonic acid, whilst the other portion enters into
combination with the hydrogen, and an oxide of a
carbohydrogen is formed,, in which all the hydrogen
is contained.
In a similar manner, when alcohol is exposed to
a gentle red heat, its carbon is shared between
the elements of the water — an oxide of a carbo-
hydrogen which contains all the oxygen, and some
gaseous compounds of carbon and hydrogen being
produced.
It is evident that during transformations caused
by heat, no foreign affinities can be in play, so that
the new compounds must result merely from the
elements arranging themselves, according to the
degree of their mutual affinities, into new combina-
tions which are constant and unchangeable in the
conditions under which they were originally formed,
but undergo changes when these conditions become
different. If we compare the products of two
bodies, similar in composition but different in pro-
perties, which are subjected to transformations by
two different causes, we find that the manner in
which the atoms are transposed, is absolutely the
same in both.
In the transformation of wood in marshy soils,
by what we call putrefaction, its carbon is shared
between the oxygen and hydrogen of its own
substance, and of the water — carburetted hydro-
240 CHEMICAL TRANSFORMATIONS
gen is consequently evolved, as well as carbonic
acid, both of which compounds have an analogous
composition (CH2, CO2).
Thus also in that transformation of sugar, which
is called fermentation, its elements are divided into
two portions ; the one, carbonic acid, which contains
f of the oxygen of sugar ; and the other, alcohol,
which contains all its hydrogen.
In the transformation of acetic acid produced by
a red heat, carbonic acid which contains f of the
oxygen of the acetic acid is formed, and acetone
which contains all its hydrogen.
It is evident from these facts, that the elements
of a complex compound are left to their special
attractions whenever their equilibrium is disturbed,
from whatever cause this disturbance may proceed.
It appears also, that the subsequent distribution of
the elements, so as to form new combinations, al-
ways takes place in the same way, with this differ-
ence only, that the nature of the products formed is
dependent upon the number of atoms of the ele-
ments which enter into action ; or in other words,
that the products differ ad infinitum, according to
the composition of the original substance.
ON THE TRANSFORMATION OF BODIES
CONTAINING NITROGEN.
When those substances are examined which are
most prone to fermentation and putrefaction, it is
found that they are all, without exception, bodies
OF BODIES CONTAINING NITROGEN. 241
which contain nitrogen. In many of these com-
pounds, a transposition of their elements occurs
spontaneously as soon as they cease to form part
of a living organism ; that is, when they are drawn
out of the sphere of attraction in which alone they
are able to exist.
There are, indeed, bodies destitute of nitrogen,
which possess a certain degree of stability only when
in combination, but which are unknown in an
isolated condition, because their elements, freed
from the power by which they were held together,
arrange themselves according to their own natural
attractions. Hypermanganic acid, manganic acid,
and hyposulphurous acid, belong to this class of
substances, which however are rare.
The case is very different with azotised bodies.
It would appear that there is some peculiarity
in the nature of nitrogen, which gives its com-
pounds the power to decompose spontaneously
with so much facility. Now, nitrogen is known
to be the most indifferent of all the elements ; it
evinces no particular attraction to any one of the
simple bodies, and this character it preserves in
all its combinations, a character which explains the
cause of its easy separation from the matters with
which it is united.
It is only when the quantity of nitrogen exceeds
a certain limit, that azotised compounds have some
degree of permanence, as is the case with melamin,
ammelin, &c. Their liability to change is also
R
242 CHEMICAL TRANSFORMATIONS
diminished, when the quantity of nitrogen is very
small in proportion to that of the other elements
with which it is united, so that their mutual
attractions preponderate.
This easy transposition of atoms is best seen in
the fulminating silvers, in fulminating mercury, in
the iodide or chloride of nitrogen, and in all fulmi-
nating compounds.
All other azotised substances acquire the same
power of decomposition, when the elements of
water are brought into play, and indeed, the
greater part of them are not capable of trans-
formation, while this necessary condition to the
transposition of their atoms is absent. Even the
compounds of nitrogen, which are most liable to
change, such as those which are found in animal
bodies, do not enter into a state of putrefaction
when dry.
The result of the known transformations of
azotised substances proves, that the water does not
merely act as a medium in which motion is per-
mitted to the elements in the act of transposition,
but that its influence depends on chemical affinity.
When the decomposition of such substances is
effected with the assistance of water, their nitrogen
is invariably liberated in the form of ammonia.
This is a fixed rule without any exceptions, what-
ever may be the cause which produces the decom-
positions. All organic compounds containing
nitrogen, evolve the whole of that element in
OF BODIES CONTAINING NITROGEN. 243
the form of ammonia when acted on by alkalies.
Acids, and increase of temperature, produce the
same effect. It is only when there is a deficiency
of water or its elements, that cyanogen or other
azotised compounds are produced.
From these facts it may be concluded, that
ammonia is the most stable compound of nitrogen ;
and that hydrogen and nitrogen possess a degree
of affinity for each other, which surpasses the
attraction of the latter body for any other element.
Already in considering the transformations of
substances containing no nitrogen, we have seen
that a powerful cause effecting the disunion of the
elements of a complex organic atom in a definite
manner, is the great affinity which carbon possesses
for oxygen. But carbon is also invariably contained
in azotised compounds, while the great affinity of
nitrogen for hydrogen furnishes a new and power-
ful cause, facilitating the transposition of their com-
ponent parts. Thus, in the bodies which do not
contain nitrogen we have one element, and in
those in which that substance is present, two
elements, which mutually share the elements of
water. Hence there are two opposite affinities
at play, which strengthen mutually each other's
action.
Now we know, that the most powerful attractions
may be overcome by the influence of two affinities.
Thus, a decomposition of alumina may be effected
with the greatest facility, when the affinity of
R 2
244 CHEMICAL TRANSFORMATIONS
charcoal for oxygen, and of chlorine for alu-
minium, are both put in action, although neither
of these alone has any influence upon it. There
is in the nature and constitution of the com-
pounds of nitrogen a kind of tension of their com-
ponent parts, and a strong disposition to yield to
transformations, which effect spontaneously the trans-
position of their atoms on the instant that water or
its elements are brought in contact with them.
The characters of the hydrated cyanic acid,
one of the simplest of all the compounds of
nitrogen, are perhaps the best adapted to convey
a distinct idea of the manner in which the atoms
are disposed of in transformations. This acid con-
tains nitrogen, hydrogen, and oxygen, in such pro-
portions, that the addition of a certain quantity of
the elements of water is exactly sufficient to cause
the oxygen contained in the water and acid to
unite with the carbon and form carbonic acid, and
the hydrogen of the water to combine with the
nitrogen and form ammonia. The most favourable
conditions for a complete transformation are,
therefore, associated in these bodies, and it is
well known, that the disunion takes place on
the instant that the cyanic acid ,and water are
brought into contact, the mixture being converted
into carbonic acid and ammonia, with brisk effer-
vescence.
This decomposition may be considered as the
type of the transformations of all azotised com-
OF BODIES CONTAINING NITROGEN. 245
pounds ; it is putrefaction in its simplest and most
perfect form, because the new products, the car-
bonic acid and ammonia, are incapable of further
transformations.
Putrefaction assumes a totally different and
much more complicated form, when the products,
which are first formed, undergo a further change.
In these cases the process consists of several stages,
of which it is impossible to determine when one
ceases and the other begins.
The transformations of cyanogen, a body com-
posed of carbon and nitrogen, and the simplest
of all the compounds of nitrogen, will convey a
clear idea of the great variety of products which are
produced in such a case : it is the only example of
the putrefaction of an azotised body which has been
at all accurately studied.
A solution of cyanogen in water becomes turbid
after a short time, and deposits a black, or brownish
Hack matter, which is a combination of ammonia
with another body, produced by the simple union
of cyanogen with water. This substance is insoluble
in water, and is thus enabled to resist further
change.
A second transformation is effected by the cya-
nogen being shared between the elements of the
water, in consequence of which cyanic acid is
formed by a certain quantity of the cyanogen
combining with the oxygen of the water, while
hydrocyanic acid is also formed by another portion
246 CHEMICAL TRANSFORMATIONS
of the cyanogen uniting with the hydrogen which
was liberated.
Cyanogen experiences a third transformation, by
which a complete disunion of its elements takes
place, these being divided between the constituents
of the water. Oxalic acid is the one product of
this disunion, and ammonia the other.
Cyanic acid, the formation of which has been
mentioned above, cannot exist in contact with
water, being decomposed immediately into carbonic
acid and ammonia. The cyanic acid, however, newly
formed in the decomposition of cyanogen, escapes
this decomposition by entering into combination
with the free ammonia, by which urea is produced.
The hydrocyanic acid is also decomposed into a
brown matter which contains hydrogen and cyano-
gen, the latter in greater proportion than it does
in the gaseous state. Oxalic acid, urea, and
carbonic acid, are also formed by its decomposition,
and formic acid and ammonia are produced by the
decomposition of its radical.
Thus, a substance into the composition of which
only two elements (carbon and nitrogen) enter,
yields eight totally different products. Several of
these products are formed by the transformation
of the original body, its elements being shared
between the constituents of water; others are
produced in consequence of a further disunion of
those first formed. The urea and carbonate of
ammonia are generated by the combination of two
OF BODIES CONTAINING NITROGEN. 247
of the products, and in their formation the whole
of the elements have assisted.
These examples show, that the results of decom-
position by fermentation or putrefaction compre-
hend very different phenomena. The first kind
of transformation is, the transposition of the
elements of one complex compound, by which new
compounds are produced with or without the
assistance of the elements of water. In the pro-
ducts newly formed in this manner, either the
same proportions of those component parts which
were contained in the matter before transformation,
are found, or with them, an excess, consisting of
the constituents of water which had assisted in pro-
moting the disunion of the elements.
The second kind of transformations consists of
the transpositions of the atoms of two or more com-
plex compounds, by which the elements of both
arrange themselves mutually into new products,
with or without the co-operation of the elements of
water. In this kind of transformations, the new
products contain the sum of the constituents of all
the compounds which had taken a part in the
decomposition.
The first of these two modes of decomposition is,
that designated fermentation, the second putrefac-
tion ; and when these terms are used in the follow-
ing pages, it will always be to distinguish the two
processes above described^ which are so different in
their results.
248 FERMENTATION
FERMENTATION OF SUGAK.
The peculiar decomposition which sugar suffers
may be viewed as a type of all the transformations
designated fermentation.
When yeast is made into a thin paste with water,
and 1 cubic centimeter of this mixture introduced
into a graduated glass receiver filled with mercury,
in which are already 10 grammes of a solution of
cane-sugar, containing 1 gramme of pure solid
sugar; it is found, after the mixture has been
exposed for 24 hours to a temperature of from
20 to 25 C. (68—77 F.), that a volume of car-
bonic acid has been formed, which, at 0° C. (32° F.)
and an atmospheric pressure indicated by 0*76
metre Bar. would be from 245 to 250 cubic centi-
meters. But to this quantity we must add 11
cubic centimeters of carbonic acid, with which
the 1 1 grammes of liquid would be saturated,
so that in all 255 — 259 cubic centimeters of
carbonic acid are obtained. This volume of car-
bonic acid corresponds to from 0*503 to 0'5127
grammes by weight. Now Thenard obtained from
100 grammes of cane-sugar 0*5262 of absolute al-
cohol. 100 parts of sugar from the cane yield,
therefore, 103*89 parts of carbonic acid and alco-
hol. The entire carbon in these products is equal
to 42 parts, which is exactly the quantity originally
contained in the sugar.
The analysis of sugar from the cane, proves that
OF SUGAR. 249
it contains the elements of carbonic acid and alcohol,
minus 1 atom of water. The alcohol and carbonic
acid produced by the fermentation of a certain quan-
tity of sugar, contain together one equivalent of oxy-
gen, and one equivalent of hydrogen, the elements,
therefore, of one equivalent of water, more than
the sugar contained. The excess of weight in the
products is thus explained most satisfactorily ; it is
owing, namely, to the elements of water having
taken part in the metamorphosis of the sugar.
It is known that 1 atom of sugar contains
12 equivalents of carbon, both from the propor-
tions in which it unites with bases, and from
the composition of saccharic acid the product of
its oxidation. Now none of these atoms of car-
bon are contained in the sugar as carbonic acid,
because the whole quantity is obtained as oxalic
acid, when sugar is treated with hypermanganate
of potash (Gregory); and as oxalic acid is a lower
degree of the oxidation of carbon than carbonic
acid, it is impossible to conceive that the lower
degree should be produced from the higher, by
means of one of the most powerful agents of oxida-
tion which we possess. "
It can be also proved, that the hydrogen of the
sugar does not exist in it in the form of alcohol,
for it is converted into water and a kind of carbon-
aceous matter, when treated with acids, particularly
with such as contain no oxygen ; and this manner
of decomposition is never suffered by a compound
of alcohol.
250 FERMENTATION OF SUGAR.
Sugar contains, therefore, neither alcohol nor
carbonic acid, so that these bodies must be pro-
duced by a different arrangement of its atoms, and
by theirninion with the elements of water.
In this metamorphosis of the sugar, the elements
of the yeast, by contact with which its fermentation
was effected, take no appreciable part in the trans-
position of the elements of the sugar ; for in the
products resulting from the action, we find no
component part of this substance.
We may now study the fermentation of a vege-
table juice, which contains not only saccharine
matter, but also such substances as albumen and
gluten. The juices of parsnips, beet-roots, and
onions, are well adapted for this purpose. When
such a juice is mixed with yeast at common tem-
peratures, it ferments like a solution of sugar. Car-
bonic acid gas escapes from it with effervescence,
and in the liquid, alcohol is found in quantity ex-
actly corresponding to that of the sugar originally
contained in the juice. But such a juice under-
goes spontaneous decomposition at a temperature
of from 95° to 104° (35° — 40° C.). Gases possessing
an offensive smell are evolved in considerable quan-
tity, and when the liquor is examined after the de-
composition is completed, no alcohol can be de-
tected. The sugar has also disappeared, and with
it all the azotised compounds which existed in the
juice previously to its fermentation. Both were
decomposed at the same time ; the nitrogen of the
azotised compounds remains in the liquid as am-
YEAST OR FERMENT. 251
monia, and, in addition to it, there are tnree new
products, formed from the component parts of
the juice. One of these is lactate acid, the slightly
volatile compound found in the animal organism ;
the other is the crystalline body which forms the
principal constituent of manna ; and the third is a
mass resembling gum-arabic, which forms a thick
viscous solution with water. These three products
weigh more than the sugar contained in the juice,
even without calculating the weight of the gaseous
products. Hence they are not produced from the
elements of the sugar alone. None of these three
substances could be detected in the juice before
fermentation. They must, therefore, have been
formed by the interchange of the elements of the
sugar with those of the foreign substances also
present. It is this mixed transformation of two or
more compounds which receives the special name
of putrefaction.
ON YEAST OR FERMENT.
When attention is directed to the condition of
those substances which possess the power of induc-
ing fermentation and putrefaction in other bodies,
evidences are found in their general characters, and
in the manner in which they combine, that they all
are bodies, the atoms of which are in the act of
transposition.
The characters of the remarkable matter which
is deposited in an insoluble state during the fer-
252 YEAST OR FERMENT,
mentation of beer, wine, and vegetable juices, may
be first studied.
This substance, which has been called yeast or
ferment, from the power which it possesses of
causing fermentation in sugar, or saccharine vege-
table juices, possesses all the characters of a com-
pound of nitrogen in the state of putrefaction and
eremacausis.
Like wood in the state of eremacausis, yeast con-
verts the oxygen of the surrounding air into carbo-
nic acid, but it also evolves this gas from its own
mass, like bodies in the state of putrefaction. (Colin.)
When kept under water, it emits carbonic acid,
accompanied by gases of an offensive smell
(Thenard), and is at last converted into a sub-
stance resembling old cheese. (Proust.) But when
its own putrefaction is completed, it has no longer
the power of inducing fermentation in other bodies.
The presence of water is quite necessary for sus-
taining the properties of ferment, for by simple
pressure its power to excite fermentation is much
diminished, and is completely destroyed by drying.
Its action is arrested also by the temperature of
boiling water, by alcohol, common salt, an excess
of sugar, oxide of mercury, corrosive sublimate,
pyroligneous acid, sulphurous acid, nitrate of silver,
volatile oils, and in short by all antiseptic sub-
stances.
The insoluble part of the substance called ferment
does not cause fermentation. For when the yeast
ITS PROPERTIES. 253
from wine or beer is carefully washed with water,
care being taken that it is always covered with
this fluid, the residue does not produce fermen-
tation.
The soluble part of ferment likewise does not excite
fermentation. An aqueous infusion of yeast may be
mixed with a solution of sugar, and preserved in
vessels from which the air is excluded, without
either experiencing the slightest change. What
then, we may ask, is the matter in ferment which
excites fermentation, if neither the soluble nor in-
soluble parts possess the power ? This question has
been answered by Colin in the most satisfactory
manner. He has shown that in reality it is the
soluble part. But before it obtains this power, the
decanted infusion must be allowed to cool in
contact with the air, and to remain some time
exposed to its action. When introduced into a
solution of sugar in this state, it produces a brisk
fermentation ; but without previous exposure to
the air, it manifests no such property.
The infusion absorbs oxygen during its exposure
to the air, and carbonic acid may be found in it
after a short time.
Yeast produces fermentation in consequence of
the progressive decomposition which it suffers from
the action of air and water.
Now when yeast is made to act on sugar, it
is found, that after the transformation of the latter
254 YEAST OR FERMENT,
substance into carbonic acid and alcohol is com-
pleted, part of the yeast itself has disappeared.
From 20 parts of fresh yeast from beer, and 100
parts of sugar, Thenard obtained, after the fer-
mentation was completed, 13*7 parts of an insolu-
ble residue, which diminished to 10 parts when
employed in the same way with a fresh portion of
sugar. These ten parts were white, possessed of
the properties of woody fibre, and had no further
action on sugar.
It is evident, therefore, that during the fermenta-
tion of sugar by yeast, both of these substances
suffer decomposition at the same time, and disappear
in consequence. But if yeast be a body which
excites fermentation by being itself in a state of
decomposition, all other matters in the same condi-
tion should have a similar action upon sugar ; and
this is in reality the case. Muscle, urine, isin-
glass, osmazome, albumen, cheese, gliadine, gluten,
legumin, and blood, when in a state of putrefaction,
have all the power of producing the putrefaction,
or fermentation of a solution of sugar. Yeast,
which by continued washing has entirely lost the
property of inducing fermentation, regains it when
its putrefaction has recommenced, in consequence
of its being kept in a warm situation for some
time.
Yeast and putrifying animal and vegetable matters
act as peroxide of hydrogen does on oxide of silver,
ITS MODE OF ACTION. 255
when they induce bodies with which they are in
contact to enter into the same state of decompo-
sition. The disturbance in the attraction of .the
constituents of the peroxide of hydrogen effects a
disturbance in the attractions of the elements of
the oxide of silver, the one being decomposed, on
account of the decomposition of the other.
Now if we consider the process of the fermenta-
tion of pure sugar, in a practical point of view, we
meet with two facts of constant occurrence. When
the quantity of ferment is too small in proportion
to that of the sugar, its putrefaction will be com-
pleted before the transformation of all the sugar is
effected. Some sugar here remains undecomposed,
because the cause of its transformation is absent,
viz. contact with a body in a state of decompo-
sition.
But when the quantity of ferment predominates,
a certain quantity of it remains after all the sugar
has fermented, its decomposition proceeding very
slowly, on account of its insolubility in water.
This residue of ferment is still able to induce fer-
mentation, when introduced into a fresh solution of
sugar, and retains the same power until it has
passed through all the stages of its own transfor-
mation.
Hence a certain quantity of yeast is necessary
in order to effect the transformation of a certain
portion of sugar, not because it acts by its quantity
increasing any affinity, but because its influence
256 YEAST OR FERMENT.
depends solely on its presence, and its presence is
necessary, until the last atom of sugar is decom-
posed.
These facts and observations point out the exist-
ence of a new cause, which effects combinations and
decompositions. This cause is the action which
bodies in a state of combination or decomposition
exercise upon substances, the component parts of
which are united together by a feeble affinity. In its
action it resembles a peculiar power, attached to a
body in the state of combination or decomposition,
but exerting its influence beyond the sphere of its
own attractions.
We are now able to account satisfactorily for
many known phenomena.
A large quantity of hippuric acid may be obtained
from the fresh urine of a horse, by the addition of
muriatic acid ; but when the urine has undergone
putrefaction, no trace of it can be discovered. The
urine of man contains a considerable quantity of
urea, but when the urine putrifies, the urea entirely
disappears. When urea is added to a solution of
sugar in the state of fermentation, it is decomposed
into carbonic acid and ammonia. No asparagin
can be detected in a putrified infusion of asparagin,
liquorice-root, or the root of alihcpa officinalis.
It has already been mentioned, that the strong
affinity of nitrogen for hydrogen, and that of car-
bon for oxygen, are the cause of the facility with
which the elements of azotised compounds are dis-
NATURE OF FERMENTATION. 257
united ; those affinities aiding each other, inasmuch
as by virtue of them different elements of the com-
pound strive to take possession of the different
elements of water. Now since it is found that no
body destitute of nitrogen possesses, when pure, the
property of decomposing spontaneously whilst in
contact with water, we must ascribe this property
which azotised bodies possess in so eminent a de-
gree, to something peculiar in the nature of the
compounds of nitrogen, and to their constituting,
in a certain measure, more highly organised atoms.
Every azotised constituent of the animal or
vegetable organism enters spontaneously into pu-
trefaction, when exposed to moisture and a high
temperature.
Azotised matters are accordingly the only causes
of fermentation and putrefaction in vegetable sub-
stances.
Putrefaction, on account of its effects, as a mixed
transformation of many different substances, may be
classed with the most powerful processes of deoxida-
tion, by which the strongest affinities are overcome.
When a solution of gypsum in water is mixed
with a decoction of sawdust, or any other organic
matter capable of putrefaction, and preserved in
well-closed vessels, it is found, after some time, that
the solution contains no more sulphuric acid, but
in its place carbonic and free hydrosulphuric acid,
between which the lime of the gypsum is shared.
In stagnant water containing sulphates in solution,
258 YEAST OR FERMENT.
crystallised pyrites is observed to form on the de-
caying roots.
Now we know that in the putrefaction of wood
under water, when air therefore is excluded, a part
of its carbon combines with the oxygen of the
water, as well as with the oxygen which the wood
itself contains ; whilst its hydrogen and that of the
decomposed water are liberated either in a pure
state, or as carburetted hydrogen. The products of
this decomposition are therefore of the same kind
as those generated when steam is conducted over
red-hot charcoal.
It is evident, that if with the water a substance
containing a large quantity of oxygen, such as sul-
phuric acid, be also present, the matters in the
state of putrefaction will make use of the oxygen of
that substance as well as that of the water, in order
to form carbonic acid ; and the sulphur and hydro-
gen being set free will combine whilst in the nas-
cent state, producing hydrosulphuric acid, which
will be again decomposed if metallic oxides be pre-
sent ; and the results of this second decomposition
will be water and metallic sulphurets.
The putrefied leaves of woad (Isatis tinctoria), in
contact with indigo-blue, water, and alkalies, suffer
further decomposition, and the indigo is deoxidised
and dissolved.
The mannite formed by the putrefaction of beet-
roots and other plants which contain sugar, con-
tains the same number of equivalents of carbon and
NATURE OF FERMENTATION. 259
hydrogen as the sugar of grapes, but two atoms
less of oxygen ; and it is highly probable that it is
produced from sugar of grapes, contained in those
plants, in precisely the same manner as indigo-blue
is converted into deoxidised white indigo.
During the putrefaction of gluten, carbonic acid
and pure hydrogen gas are evolved; phosphate,
acetate, caseate, and lactate of ammonia being at
the same time produced in such quantity, that the
further decomposition of the gluten ceases. But
when the supply of water is renewed, the decom-
position begins again, and in addition to the salts
just mentioned, carbonate of ammonia and a white
crystalline matter resembling mica (caseous oxide)
are formed, together with hydrosulphate of am-
monia, and a mucilaginous substance coagulable
by chlorine. Lactic acid is almost always pro-
duced by the putrefaction of organic bodies.
We may now compare fermentation and pu-
trefaction with the decomposition which organic
compounds suffer under the influence of a high
temperature. Dry distillation would appear to be a
process of combustion or oxidation going on in the
interior of a substance, in which a part of the carbon
unites with all or part of the oxygen of the com-
pound, while other new compounds containing a
large proportion of hydrogen are necessarily pro-
duced. Fermentation may be considered as a
process of combustion or oxidation of a similar kind,
taking place in a liquid between the elements of
s2
260 EREMACAUSIS OR DECAY.
the same matter, at a very slightly elevated temper-
ature ; and putrefaction as a process of oxidation,
in which the oxygen of all the substances present
comes into play.
EREMACAUSIS OR DECAY. v
In organic nature, besides the processes of de-
composition named fermentation and putrefaction,
another and not less striking class of changes oc-
cur, which bodies suffer from the influence of the
air. This is the act of gradual combination of the
combustible elements of a body with the oxygen of
the air ; a slow combustion or oxidation, to which
we shall apply the term of eremacausis.
The conversion of wood into humus, the forma-
tion of acetic acid out of alcohol, nitrification, and
numerous other processes, are of this nature. Vege-
table juices of every kind, parts of animal and vege-
table substances, moist sawdust, blood, &c., cannot
be exposed to the air, without suffering immediately
a progressive change of colour and properties,
during which oxygen is absorbed These changes
do not take place when water is excluded, or when
the substances are exposed to the temperature of
32°, and it has been observed that different bodies
require different degrees of heat, in order to effect
the absorption of oxygen, and, consequently, their
eremacausis. The property of suffering this change
is possessed in the highest degree by substances
which contain nitrogen.
CONDITIONS FOR ITS OCCURRENCE. 261
When vegetable juices are evaporated by a gentle
heat in the air, a brown or brownish-black sub-
stance is precipitated as a product of the action of
oxygen upon them. This substance, which appears
to possess similar properties from whatever juice it
is obtained, has received the name of extractive
matter; it is insoluble or very sparingly soluble in
water, but is dissolved with facility by alkalies. By
the action of air on solid animal or vegetable mat-
ters, a similar pulverulent brown substance is
formed, and is known by the name of humus.
(Terreau.)
The conditions which determine the commence-
ment of eremacausis are of various kinds. Many
organic substances, particularly such as are mix-
tures of several more simple matters, oxidise in the
air when simply moistened with water ; others not
until they are subjected to the action of alkalies ;
but the greatest part of them undergo this state
of slow combustion or oxidation, when brought in
contact with other decaying matters.
The eremacausis of an organic matter is retarded
or completely arrested by all those substances
which prevent fermentation or putrefaction. Min-
eral acids, salts of mercury, aromatic substances,
empyreumatic oils, and oil of turpentine, possess
a similar action in this respect. The latter sub-
stances have the same effect on decaying bodies
as on phosphuretted hydrogen, the spontaneous
inflammability of which they destroy.
262 EREMACAUSIS OR DECAY.
Many bodies which do not decay when moistened
with water, enter into eremacausis when in contact
with an alkali. Gallic acid, haematin, and many
other compounds, may be dissolved in water and
yet remain unaltered, but if the smallest quantity of
a free alkali is present, they acquire the property of
attracting oxygen, and are converted into a brown
substance like humus, evolving very frequently at
the same time carbonic acid. (Chevreul.)
A very remarkable kind of eremacausis takes
place in many vegetable substances, when they are
exposed to the influence of air, water, and ammonia.
They absorb oxygen very rapidly, and form splendid
violet or red-coloured liquids, as in the case of orcin
and erythrin. They now contain an azotised sub-
stance, not in the form of ammonia.
All these facts show that the action of oxygen
seldom affects the carbon of decaying substances,
and this corresponds exactly to what happens in
combustion at high temperatures. It is well known,
for example, that when no more oxygen is admitted
to a compound of carbon and hydrogen than is suf-
ficient to combine with its hydrogen, the carbon is
not burned, but is separated as lamp-black ; while,
if the quantity of oxygen is not sufficient even to
consume all the hydrogen, new compounds are
formed, such as naphthalin and similar matters,
which contain a smaller proportion of hydrogen than
those compounds of carbon and hydrogen which
previously existed in the combustible substance.
NATURE OF THE PROCESS. 263
There is no example of carbon combining di-
rectly with oxygen at common temperatures, but
numerous facts show that hydrogen, in certain states
of condensation, possesses that property. Lamp-
black which has been heated to redness may be
kept in contact with oxygen gas, without forming
carbonic acid ; but lamp-black, impregnated with
oils which contain a large proportion of hydrogen,
gradually becomes warm, and inflames sponta-
neously. The spontaneous inflammability of the
charcoal used in the fabrication of gunpowder has
been correctly ascribed to the hydrogen which it
contains in considerable quantity ; for during its
reduction to powder, no trace of carbonic acid
can be detected in the air surrounding it; it is
not formed until the temperature of the mass has
reached the red heat. The heat which produces
the inflammation is therefore not caused by the
oxidation of the carbon.
The substances which undergo eremacausis may
be divided into two classes. The first class com-
prehends those substances which unite with the
oxygen of the air, without evolving carbonic acid ;
and the second, such as emit carbonic acid by ab-
sorbing oxygen.
When the oil of bitter almonds is exposed to the
air, it absorbs two equivalents of oxygen, and is
converted into benzoic acid ; but half of the oxygen
absorbed combines with the hydrogen of the oil,
264 EREMACAUSIS OR DECAY.
and forms water, which remains in union with the
anhydrous benzoic acid.
According to the experiments of Dobereiner, 160
parts of pyrogallic acid absorb 38*09 parts of oxygen
when in contact with ammonia and water ; the
acid being changed in consequence of this absorp-
tion into a mouldy substance, which contains less
oxygen than the acid itself. It is evident that the
substance which is formed is not a higher oxide ;
and it is found, on comparing the quantity of the
oxygen absorbed with that of 'the hydrogen con-
tained in the acid, that they are exactly in the pro-
portions for forming water.
When colourless orcin is exposed together with
ammonia to the contact of oxygen gas, the beauti-
ful red- coloured orcein is produced. Now, the
only changes which take place here are, that the
absorption of oxygen by the elements of orcin and
ammonia causes the formation of water ; 1 equiva-
lent of orcin CIS H12 O8, and I equivalent of
ammonia, NH3 absorb 5 equivalents of oxygen, and
5 equivalents of water are produced, the composition
of orcein being CIS H 10 O8 N. (Dumas.) In this
case it is evident, that the oxygen absorbed has
united merely with the hydrogen.
But, although it appears very probable that the
oxygen acts primarily and principally upon hydro-
gen, the most combustible constituent of organic
matter in the state of decay ; still it cannot thence
NATURE OF THE PROCESS. 265
be concluded that the carbon is quite devoid of the
power to unite with oxygen, when every particle
of it is surrounded with hydrogen, an element
with which the oxygen combines with greater
facility.
We know, on the contrary, that nitrogen, which
cannot be made to combine with oxygen directly,
is oxidised and forms nitric acid, when mixed with
a large quantity of hydrogen, and burned in oxygen
gas. In this case its affinity is evidently increased
by the combustion of the hydrogen, which is in
fact communicated to it. It is conceivable, that,
in a similar manner, the carbon may be directly
oxidised in several cases, obtaining from its contact
with hydrogen in eremacausis a property which
it does not itself possess at common temperatures.
But the formation of carbonic acid during the
eremacausis of bodies which contain hydrogen,
must in most cases be ascribed to another cause.
It appears to be formed in a manner similar to the
formation of acetic acid, by the eremacausis of
saiiculite of potash. This salt, when exposed to
a moist atmosphere, absorbs 3 atoms of oxyen ;
melanic acid is produced, a body resembling
humus, in consequence of the formation of which,
the elements of 1 atom of acetic acid are separated
from the saliculous acid.
An alkaline solution of hsematin being exposed
to an atmosphere of oxygen, 0*2 Grm. absorb 28*6
cubic centimeters of oxygen gas in twenty-four
266 EREMACAUSIS OR DECAY.
hours, the alkali acquiring at the same time 6
cubic centimeters of carbonic acid. (Chevreul.)
But these 6 »cubic4 centimeters of carbonic acid
contain only an equal volume of oxygen, so that
it is certain from this experiment that f of
the oxygen absorbed have not united with the
carbon. It is highly probable, that during the
oxidation of the hydrogen, a portion of the carbon
had united with the oxygen contained in the
haematin, and had separated from the other
elements as carbonic acid.
The experiments of De Saussure upon the
decay of woody fibre show that such a sepa-
ration is quite possible. Moist woody fibre
evolved one volume of carbonic acid for every
volume of oxygen which it absorbed. It has just
been mentioned that carbonic acid contains its
own volume of oxygen. Now, woody fibre con-
tains carbon and the elements of water, so that
the result of the action of oxygen upon it is
exactly the same as if pure charcoal had combined
directly with oxygen. But the characters of woody
fibre show, that the elements of water are not
contained in it in the form of water ; for, were
this the case, starch, sugar, and gum, must also
be considered as hydrates of carbon.
But if the hydrogen does not exist in woody
fibre in the form of water, the direct oxidation
of the carbon cannot be considered as at all
probable, without rejecting all the facts established
NATURE OF THE PROCESS. 267
by experiment regarding the process of combus-
tion at low temperatures.
If we examine the action of oxygen upon such a
substance as alcohol which contains a large quantity
of hydrogen, we find most distinctly, that the
direct formation of carbonic acid is the last stage
of its oxidation, and that it is preceded by a series
of changes, the last of which is a complete com-
bustion of the hydrogen. Aldehyde, acetic acid,
formic acid, oxalic acid, and carbonic acid, form
a connected chain of products arising from the
oxidation of alcohol; and the successive changes
which this fluid experiences from the action of oxy-
gen may be readily traced in them. Aldehyde is
alcohol minus hydrogen ; acetic acid is formed by
the direct union of aldehyde with oxygen. Formic
acid and water are formed by the union of acetic
acid with oxygen. When all the hydrogen is
removed from this formic acid, oxalic acid is pro-
duced ; and the latter acid is converted into
carbonic acid by uniting with an additional portion
of oxygen. All these products appear to be formed
simultaneously, by the action of oxidising agents on
alcohol ; but it can scarcely be doubted, that the
formation of the last product, the carbonic acid,
does not take place until all the hydrogen has been
abstracted.
The absorption of oxygen by drying oils certainly
does not depend upon the oxidation of their carbon ;
for in raw nut-oil, for example, which was not free
268 EREMACAUSIS OR DECAY.
from mucilage and other substances,, only twenty-
one volumes of carbonic acid were formed for every
146 volumes of oxygen gas absorbed.
It must be remembered, that combustion or oxi-
dation at low temperatures produces results quite
similar to combustion at high temperatures with
limited access of air. The most combustible element
of a compound, which is exposed to the action of
oxygen, must become oxidized first, for its superior
combustibility is caused by its being enabled to unite
with oxygen at a temperature at which the other
elements cannot enter into that combination ; this
property having the same effect as a greater affinity.
The combustibility of potassium is no measure
of its affinity for oxygen ; we have reason to
believe that the attraction of magnesium and
aluminium for oxygen is greater than that of potas-
sium for the same element ; but neither of those
metals oxidises either in air or water at common
temperatures, whilst potassium decomposes water
with great violence, and appropriates its oxygen.
Phosphorus and hydrogen combine with oxygen
at ordinary temperatures, the first in moist air, the
second, when in contact with finely-divided plati-
num ; while charcoal requires a red heat before it
can enter into combination with oxygen. It is
evident that phosphorus and hydrogen are more
combustible than charcoal, that is, that their affi-
nity for oxygen at common temperatures is greater ;
and this is not the less certain, because it is found,
NATURE OF THE PROCESS. 269
that carbon in certain other conditions shows a
much greater affinity for oxygen than either of
those substances.
In putrefaction, the conditions are evidently
present, under which the affinity of carbon for
oxygen comes into play ; neither expansion, cohe-
sion, nor the gaseous state, opposes it, whilst in ere-
macausis all these restraints have to be overcome.
The evolution of carbonic acid during the decay
or eremacausis of animal or vegetable bodies,
which are rich in hydrogen, must accordingly be
ascribed to a transposition of the elements or dis-
turbance in their attractions, similar to that which
gives rise to the formation of carbonic acid in the
processes of fermentation and putrefaction.
The eremacausis of such substances is, therefore,
a decomposition analogous to the putrefaction of
azotised bodies. For in these there are two affini-
ties at play ; the affinity of nitrogen for hydrogen,
and that of carbon for oxygen, which facilitate the
disunion of the elements. Now there are two
affinities also in action in those bodies which decay
with the evolution of carbonic acid. One of these
affinities is the attraction of the oxygen of the air
for the hydrogen of the substance, which corre-
sponds to the attraction of nitrogen for the same
element ; and the other is the affinity of the
carbon of the substance for its oxygen, which is
constant under all circumstances.
When wood putrefies in marshes, carbon and
270 EREMACAUSIS OR DECAY.
oxygen are separated from its elements in the form
of carbonic acid, and hydrogen in the form of carbu-
retted hydrogen. But when wood decays or putre-
fies in the air, its hydrogen does not combine with
carbon, but with oxygen, for which it has a much
greater affinity at common temperatures.
Now it is evident from the complete similarity
of these processes, that decaying and putrefying
bodies can mutually replace one another in their
reciprocal actions.
All putrefying bodies pass into the state of decay
when exposed freely to the air ; and all decaying
matters into that of putrefaction, when air is
excluded. All bodies, likewise, in a state of decay
are capable of inducing putrefaction in other bodies
in the same manner as putrefying bodies them-
selves do.
EREMACAUSIS OR DECAY OF BODIES WHICH
DO NOT CONTAIN NITROGEN I FORMATION OF
ACETIC ACID.
ALL those substances which appear to possess the
property of entering spontaneously into fermenta-
tion and putrefaction, do not in reality suifer those
changes without some previous disturbance in the
attraction of their elements. Eremacausis always
precedes fermentation and putrefaction, and it is not
until after the absorption of a certain quantity of
oxygen that the signs of a transformation in the
interior of the substances show themselves.
OF BODIES DESTITUTE OF NITROGEN. 271
It is a very general error to suppose that organic
substances have the power of undergoing change
spontaneously, without the aid of an external cause.
When they are not in a state of change, it is neces-
sary, before they can assume that state, that the
existing equilibrium of their elements should be
disturbed; and the most common cause of this
disturbance is undoubtedly the atmosphere which
surrounds all bodies.
The juices of the fruit or other part of a plant
which very readily undergo decomposition, retain
their properties unchanged as long as they are pro-
tected from immediate contact with the air, that is
as long as the cells or organs in which they are
contained resist the influence of the air. It is not
until after the juices have been exposed to the air,
and have absorbed a certain quantity of oxygen,
that the substances dissolved in them begin to be
decomposed.
The beautiful experiments of Gay-Lussac upon
the fermentation of the juice of grapes, as well as
the important practical improvements to which they
have led, are the best proofs of the atmosphere
having an influence upon the changes of organic
substances. The juice of grapes which were
expressed under a receiver filled with mercury, so
that air was completely excluded, did not ferment.
But when the smallest portion of air was introduced,
a certain quantity of oxygen became absorbed, and
fermentation immediately began. When the juice
272 EREMACAUSIS OR DECAY.
was expressed from the grapes in contact with air,
under the conditions therefore necessary to cause
its fermentation, still this change did not ensue
when the juice was heated in close vessels to the
temperature of boiling water. When thus treated,
it could be preserved for years without losing its
property of fermenting. A fresh exposure to the
air at any period caused it to ferment.
Animal food of every kind, and even the most
delicate vegetables, may be preserved unchanged
if heated to the temperature of boiling water in
vessels from which the air is completely excluded.
Food thus prepared has been kept for fifteen years,
and upon opening the vessels after this long time,
has been found as fresh and well flavoured as when
originally placed in them.
The action of the oxygen in these processes of
decomposition is very simple ; it excites changes
in the composition of the azotised matters dissolved
in the juices ; — the mode of combination of the
elements of those matters undergoes a disturbance
and change in consequence of their contact with
oxygen. The oxygen acts here in a similar manner
to the friction or motion which effects the mutual
decomposition of two salts, the crystallisation of
salts from their solution, or the explosion of fulmi-
nating mercury. It causes the state of rest to be
converted into a state of motion.
When this condition of intestine motion is once
excited, the presence of oxygen is no longer
OF BODIES DESTITUTE OF NITROGEN. 273
necessary. The smallest particle of an azotised
body in this act of decomposition exercises an
influence upon the particles in contact with it, and
the state of motion is thus propagated through the
substance. The air may now be completely excluded,
but the fermentation or putrefaction proceeds unin-
terruptedly to its completion. It has been remarked
that the mere contact of carbonic acid is sufficient
to produce fermentation in the juices of several
fruits.
The contact of ammonia and alkalies in general
may be mentioned amongst the chemical condi-
tions which determine the commencement of
eremacausis ; for their presence causes many
substances to absorb oxygen and to decay, in
which neither oxygen nor alkalies alone produce
that change.
Thus alcohol does not combine with the oxygen
of the air at common temperatures. But a solution
of potash in alcohol absorbs oxygen with much
rapidity, and acquires a brown colour. The alcohol
is found after a short time to contain acetic acid,
formic acid, and the products of the decomposition
of aldehyde by alkalies, including aldehyde resin,
which gives the liquid a brown colour.
The most general condition for the production of
eremacausis in organic matter is contact with a
body already in the state of eremacausis or putre-
faction. We have here an instance of true conta-
274 EREMACAUSIS OR DECAY
gion ; for the communication of the state of com-
bustion is in reality the effect of the contact.
It is decaying wood which causes fresh wood
around it to assume the same condition, and it is
the very finely divided woody fibre in the act of
decay, which in moistened gall-nuts converts the
tannic acid with such rapidity into gallic acid.
A most remarkable and decided example of this
induction of combustion has been observed by De
Samsure. It has already been mentioned, that
moist woody fibre, cotton, silk, or vegetable mould,
in the act of fermentation or putrefaction, converts
oxygen gas which may surround it into carbonic
acid, without change of volume. Now, De Sam-
sure added a certain quantity of hydrogen gas to
the oxygen, and observed a diminution in volume
immediately after the addition. A part of the
hydrogen gas had disappeared, and along with it a
portion of the oxygen, but a corresponding quantity
of carbonic acid gas had not been formed. The
hydrogen and oxygen had disappeared in exactly
the same proportion as that in which they combine
to form water ; a true combustion of the hydrogen,
therefore, had been induced by mere contact with
matter in the state of eremacausis. The action of the
decaying substance here produced results exactly
similar to those effected by spongy platinum ; but
that they proceeded from a different cause was shown
by the fact,that the presence of carbonic oxide,which
OF BODIES DESTITUTE OF NITROGEN.
arrests completely the action of platinum on
carburetted hydrogen, did not retard in the
slightest degree the combustion of the hydrogen in
contact with the decaying bodies.
But the same bodies were found by De Saussure
not to possess the property just described, before
they were in a state of fermentation or decay ; and
he has shown that even when they are in this state,
the presence of antiseptic matter destroys com-
pletely all their influence.
Let us suppose a volatile substance containing a
large quantity of hydrogen, to be substituted for
the hydrogen gas in De Saussure's experiments.
Now, the hydrogen in such compounds being con-
tained in a state of greater condensation would
suffer a more rapid oxidation, that is, its combus-
tion would be sooner completed. This principle is
in reality attended to in the manufactories in which
acetic acid is prepared according to the new plan.
In the process there adopted all the conditions are
afforded for the eremacausis of alcohol, and for its
consequent conversion into acetic acid.
The alcohol is exposed to a moderate heat, and
spread over a very extended surface, but these
conditions are not sufficient to effect its oxidation.
The alcohol must be mixed with a substance which
is with facility changed by the oxygen of the air,
and either enters into eremacausis by mere contact
with oxygen, or by its fermentation or putrefac-
tion yields products possessed of this property.
T2
276 EREMACAUSIS OR DECAY
A small quantity of beer, acescent wine, a decoc-
tion of malt, honey, and numerous other substances
of this kind, possess the action desired.
The difference in the nature of the substances
which possess this property shows, that none of
them can contain a peculiar matter which has the
property of exciting eremacausis ; they are only the
bearers of an action, the influence of which extends
beyond the sphere of its own attractions. Their
power consists in a condition of decomposition or
eremacausis, which impresses the same condition
upon the atoms of alcohol in its vicinity ; exactly
as in the case of an alloy of platinum and silver
dissolving in nitric acid, in which the platinum be-
comes oxidised, by virtue of an inductive action
which the silver in the act of its oxidation exercises
upon it. The hydrogen of the alcohol is oxidised
at the expense of the oxygen in contact with it, and
forms water, evolving heat at the same time ; the re-
sidue is aldehyde, a substance which has as great an
affinity for oxygen as sulphurous acid, and combines,
therefore, directly with it, producing acetic acid.
EREMACAUSIS OF SUBSTANCES CONTAINING
NITROGEN. NITRIFICATION.
WHEN azotised substances are burned at high
temperatures, their nitrogen does not enter into
direct combination with oxygen. The knowledge of
this fact is of assistance in considering the process
of the eremacausis of such substances. Azotised
OF BODIES CONTAINING NITROGEN. 277
organic matter always contains carbon and hydro-
gen, both of which elements have a very strong
affinity for oxygen.
Now nitrogen possesses a very feeble affinity for
that element, so that its compounds during their
combustion present analogous phenomena to those
which are observed in the combustion of substances
containing a large proportion of hydrogen and car-
bon ; a separation of the carbon of the latter sub-
stances in an uncombined state takes place, and in
the same way the substances containing nitrogen
give out that element in its gaseous form.
When a moist azotised animal matter is exposed
to the action of the air, ammonia is always liberated,
and nitric acid is never formed.
But when alkalies or alkaline bases are present,
a union of oxygen with the nitrogen takes place
under the same circumstances, and nitrates are
formed together with the other products of oxi-
dation.
Although we see the most simple means and
direct methods employed in the great processes of
decomposition which proceed in nature, still we
find that the final result depends on a succession
of actions, which are essentially influenced by the
chemical nature of the bodies submitted to decom-
position.
When it is observed that the character of a sub-
stance remains unaltered in a whole series of phe-
nomena, there is no reason to ascribe a new cha-
278 EREMACAUSIS OR DECAY
racter to it, for the purpose of explaining a single
phenomenon, especially where the explanation of
that according to known facts offers no difficulty.
The most distinguished philosophers suppose
that the nitrogen in an animal substance, when ex-
posed to the action of air, water, and alkaline bases,
obtains the power to unite directly with oxygen,
and form nitric acid, but we are not acquainted
with a single fact which justifies this opinion. It
is only by the interposition of a large quantity of
hydrogen in the state of combustion or oxidation,
that nitrogen can be converted into an oxide.
When a compound of nitrogen and carbon, such
as cyanogen, is burned in oxygen gas, its carbon
alone is oxidised ; and when it is conducted over a
metallic oxide heated to redness^ an oxide of nitro-
gen is very rarely produced, and never when the
carbon is in excess. 'Kuhlmann found in his ex-
periments, that it was only when cyanogen was
mixed with an excess of oxygen gas, and conducted
over spongy platinum, that nitric acid was gene-
rated.
Kuhlmann could not succeed in causing pure
nitrogen to combine directly with oxygen, even
under the most favourable circumstances ; thus, with
the aid of spongy platinum at different tempera-
tures, 'no union took place.
The carbon in the cyanogen gas must, there-
fore, have given rise to the combustion of the ni-
trogen by induction.
OF BODIES CONTAINING NITROGEN. 279
On the other hand we find that ammonia, which
is a compound of hydrogen and nitrogen, cannot
be exposed to the action of oxygen, without the
formation of an oxide of nitrogen, and in conse-
quence the production of nitric acid.
It is owing to the great facility with which am-
monia is converted into nitric acid, that it is so
difficult to obtain a correct determination of the
quantity of nitrogen in a compound subjected to
analysis, in which it is either contained in the form
of ammonia, or from which ammonia is formed by
an elevation of temperature. For when ammonia is
passed over red-hot oxide of copper, it is converted,
either completely or partially, into binoxide of
nitrogen.
When ammoniacal gas is conducted over per-
oxide of manganese or iron heated to redness, a
large quantity of nitrate of ammonia is obtained,
if the ammonia be in excess ; and the same decom-
position happens, when ammonia and oxygen are
together passed over red-hot spongy platinum.
It appears, therefore, that the combination of
oxygen with nitrogen occurs rarely during the com-
bustion of compounds of the latter element with
carbon, but that nitric acid is always a product
when ammonia is present in the substance exposed
to oxidation.
The cause wherefore the nitrogen in ammonia ex-
hibits such a strong disposition to become converted
into nitric acid is undoubtedly, that the two products,
which are the result of the oxidation of the consti-
280 EREMACAUSIS OR DECAY
tuents of ammonia, possess the power of uniting
with one another. Now this is not the case in the
combustion of compounds of carbon and nitrogen ;
here one of the products is carbonic acid, which,
on account of its gaseous form, must oppose the
combination of the oxygen and nitrogen, by pre-
venting their mutual contact, while the superior
affinity of its carbon for the oxygen during the act
of its formation will aid in this effect.
When sufficient access of air is admitted during
the combustion of ammonia, water is formed as
well as nitric acid, and both of these bodies com-
bine together. The presence of water may, indeed,
be considered as one of the conditions of nitrifica-
tion, since nitric acid cannot exist without it.
Eremacausis is a kind of putrefaction, differing
from the common process of putrefaction, only in
the part which the oxygen of the air plays in the
transformations of the body in decay. When this
is remembered, and when it is considered, that in
the transposition of the elements of azotised bodies
their nitrogen assumes the form of ammonia, and
that in this form, nitrogen possesses a much
greater disposition to unite with oxygen than it
has in any of its other compounds ; we can with
difficulty resist the conclusion, that ammonia is the
general cause of nitrification on the surface of the
earth.
Azotised animal matter is not, therefore, the
immediate cause of nitrification, it contributes to
OF BODIES CONTAINING NITROGEN. 281
the production of nitric acid only in so far as it is a
slow and continued source of ammonia.
Now it has been shown in the former part of this
work, that ammonia is always present in the atmo-
sphere, so that nitrates might thence be formed in
substances which themselves contained no azotised
matter. It is known also, that porous substances
possess generally the power of condensing ammonia ;
there are few ferruginous earths which do not evolve
ammoniacal products when heated to redness, and
ammonia is the cause of the peculiar smell per-
ceived upon moistening aluminous minerals. Thus,
ammonia, by being a constituent of the atmosphere,
is a very widely diffused cause of nitrification, which
will come into play whenever the different conditions
necessary for the oxidation of ammonia are com-
bined. It is probable that other organic bodies in
the state of eremacausis are the means of causing
the combustion of ammonia ; at all events, the cases
are very rare, in which nitric acid is generated from
ammonia, in the absence of all matter capable of
eremacausis.
From the preceding observations on the causes of
fermentation, putrefaction, and decay, we may now
draw several conclusions calculated to correct the
views generally entertained respecting the fermen-
tation of wine and beer, and several other impor-
tant processes of decomposition which occur in
nature.
282 VINOUS FERMENTATION.
ON VINOUS FERMENTATION : — WINE AND BEER.
It has already been mentioned, that fermenta-
tion is excited in the juice of grapes by the access
of air ; alcohol and carbonic acid being formed by
the decomposition of the sugar contained in the
fluid. But it was also stated, that the process once
commenced, continues until all the sugar is com-
pletely decomposed, quite independently of any
further influence of the air.
In addition to the alcohol and carbonic acid
formed by the fermentation of the juice, there is
also produced a yellow or grey insoluble substance,
which contains a large quantity of nitrogen. It is
this body which possesses the power of inducing
fermentation in a new solution of sugar, and which
has in consequence received the name si ferment.
The alcohol and carbonic acid are produced from
the elements of the sugar, and the ferment from
those azotised constituents of the grape juice, which
have been termed gluten, or vegetable albumen.
According to the experiments of De Saussure,
fresh impure gluten evolved, in five weeks, twenty-
eight times its volume of a gas of which f consisted
of carbonic acid, and £ of pure hydrogen gas ;
ammoniacal salts of several organic acids were
formed at the same time. Water must, therefore,
be decomposed during the putrefaction of gluten ;
the oxygen of this water must enter into combina-
tion with some of its constituents, whilst hydrogen
REPRODUCTION OF YEAST. 283
is liberated, a circumstance which happens only in
decompositions of the most energetic kind. Neither
ferment nor any substance similar to it is formed in
this case ; and we have seen that in the fermenta-
tion of saccharine vegetable juices, no escape of
hydrogen gas takes place.
It is evident that the decomposition which gluten
suffers in an isolated state,, and that which it under-
goes when dissolved in a vegetable juice, belong to
two different kinds of transformations. There is
reason to believe that its change to the insoluble
state depends upon an absorption of oxygen, for its
separation in this state may be effected under cer-
tain conditions, by free exposure to the air, without
the presence of fermenting sugar. It is known also
that the juice of grapes, or vegetable juices in gene-
ral, become turbid when in contact with air, before
fermentation commences; and this turbidity is owing
to the formation of an insoluble precipitate of the
same nature as ferment.
From the phenomena which have been observed
during the fermentation of wort *, it is known with
perfect certainty that ferment is formed from gluten
at the same time that the transformation of the
sugar is effected ; for the wort contains the azotised
matter of the corn, namely, gluten in the same
condition as it exists in the juice of grapes. The
wort ferments by the addition of yeast, but after
* Wort is an infusion of malt ; it consists of insoluble parts of this
substance dissolved in water. — TRANS.
284 VINOUS FERMENTATION.
its decomposition is completed, the quantity of fer-
ment or yeast is found to be thirty times greater
than it was originally.
Yeast from beer and that from wine, examined
under the microscope, present the same form and
general appearance. They are both acted on in
the same manner by alkalies and acids, and possess
the power of inducing fermentation anew in a
solution of sugar ; in short, they must be considered
as identical.
The fact that water is decomposed during the
putrefaction of gluten has been completely proved.
The tendency of the carbon of the gluten to appro-
priate the oxygen of water must also always be in
action, whether the gluten is decomposed in a
soluble or insoluble state. These considerations,
therefore, as well as the circumstance which all the
experiments made on this subject appear to point out,
that the conversion of gluten to the insoluble state
is the result of oxidation, lead us to conclude that
the oxygen consumed in this process is derived
from the elements of water, or from the sugar which
contains oxygen and hydrogen in the same propor-
tion as water. At all events, the oxygen thus con-
sumed in the fermentation of wine and beer is not
taken from the atmosphere.
The fermentation of pure sugar in contact with
yeast must evidently be a very different process
from the fermentation of wort or must *.
* The liquid expressed from grapes when fully ripe is called must.
OILY AND ETHEREAL PRODUCTS. 285
In the former case, the yeast disappears during the
decomposition of the sugar; but in the latter, a
transformation of gluten is effected at the same
time, by which ferment is generated. Thus yeast
is destroyed in the one case, but is formed in the
other.
Now since no free hydrogen gas can be detected
during the fermentation of beer and wine, it is evi-
dent that the oxidation of the gluten, that is, its
conversion into ferment, must take place at the
cost either of the oxygen of the water, or of that of
the sugar ; whilst the hydrogen which is set free
must enter into new combinations, or by the deoxi-
dation of the sugar, new compounds containing a
large proportion of hydrogen, and small quantity
of oxygen, together with the carbon of the sugar,
must be formed.
It is well known that wine and fermented liquors
generally contain, in addition to the alcohol, other
substances which could not be detected before their
fermentation, and which must have been formed,
therefore, during that process in a manner similar to
the production of mannite. The smell and taste
which distinguish wine from all other fermented
liquids are known to depend upon an ether of a vola-
tile and highly combustible acid, which is of an oily
nature, and to which the name of (Enanthic ether
has been given. It is also ascertained that the smell
and taste of brandy from corn and potatoes is owing
to a peculiar oil, the oil of potatoes. This oil is
286 VINOUS FERMENTATION.
more closely allied to alcohol in its properties, than
to any other organic substance.
These bodies are products of the deoxidation of
the substances dissolved in the fermenting liquids ;
they contain less oxygen than sugar or gluten, but
are remarkable for the large quantity of hydrogen
which enters into their composition.
(Enanthic acid contains an equal number of
equivalents of carbon and hydrogen, exactly the
same proportions of these elements, therefore, as
sugar, but by no means the same proportion of
oxygen. The oil of potatoes contains much more
hydrogen.
Although it cannot be doubted that these volatile
liquids are formed by a mutual interchange of the
elements of gluten and sugar, in consequence,
therefore, of a true process of putrefaction, still it
is certain, that other causes exercise an influence
upon their production and peculiarities.
The substances in wine to which its taste and
smell are owing are generated during the fermen-
tation of the juice of such grapes as contain a certain
quantity of tartaric acid ; they are not found in
wines which are free from all acid, or which con-
tain a different organic acid, such as acetic acid.
The wines of warm climates possess no odour ;
wines grown in France have it in a marked degree,
but in the wines from the Rhine the perfume is
most intense. The kinds of grapes on the Rhine,
which ripen very late, and scarcely ever completely,
OILY AND ETHEREAL PRODUCTS. 287
such as the Riessling and Orleans, have the strongest
perfume or bouquet, and contain, proportionally, a
larger quantity of tartaric acid. The earlier grapes,
such as the Rulander, and others, contain a large
proportion of alcohol, and are similar to Spanish
wines in their flavour, but they possess no bouquet.
The grapes grown at the Cape from Riesslings
transplanted from the Rhine, produce an excellent
wine, which does not however possess the aroma
which distinguishes Rhenish wine.
It is evident from these facts, that the acid of
wines, and their characteristic perfumes, have some
connexion, for they are always found together, and
it can scarcely be doubted that the presence of the
former exercises a certain influence on the forma-
tion of the latter. This influence is very plainly
observed in the fermentation of liquids, which are
quite free from tartaric acid, and particularly of
those which are nearly neutral or alkaline, such
as the mash* of potatoes or corn.
The brandy obtained from corn and potatoes
contains an ethereal oil of a similar composition
in both, to which these liquors owe their peculiar
smell. This oil is generated during the fermenta-
tion of the mash ; it exists ready formed in the fer-
mented liquids, and distils over with alcohol, when
a gentle heat is applied.
It is observed that a greater quantity of alcohol
* Mash is the mixture of malt, potatoes, and water, in the mash tun,
a large vessel in which it is infused. — TRANS.
288 VINOUS FERMENTATION.
is obtained when the mash is made quite neutral by
means of ashes or carbonate of lime, but that the
proportion of oil in the brandy is also increased.
Now it is known that brandy made from potato
starch, which has been converted into sugar by
dilute sulphuric acid, is completely free from the
potato oil, so that this substance must be gene-
rated in consequence of a change suffered by the
cellular tissue of the potatoes during their fermen-
tation.
Experience has shown that the simultaneous
fermentation or putrefaction of the cellular tissue,
by which this oil is generated, may be completely
prevented in the fabrication of brandy from corn.*
The same malt, which in the preparation of
brandy yields a fluid containing the oil of which
we are speaking, affords in the formation of beer
a spirituous liquor, in which no trace of that
oil can be detected. The principal difference in the
preparation of the two liquids is, that in the fermen-
tation of wort, an aromatic substance (hops) is
added, and it is certain that its presence modifies
the transformations which take place. Now it is
known, that the volatile oil of mustard, and the
empyreumatic oils, arrest completely the action of
yeast ; and although the oil of hops does not possess
* In the manufactory of M. Dubrunfaut, so considerable a quantity
of this oil is obtained under certain circumstances from brandy made
from potatoes, that it might be employed for the purpose of illumina-
ting his whole manufactory.
OILY AND ETHEREAL PRODUCTS. 289
this property, still it diminishes, in a great de-
gree, the influence of decomposing azotised bodies
upon the conversion of alcohol into acetic acid.
There is, therefore, reason to believe that some aro-
matic substances, when added to fermenting mix-
tures, are capable of producing very various modi-
fications in the nature of the products generated.
Whatever opinion, however, may be held regard-
ing the origin of the volatile odoriferous substances
obtained in the fermentation of wine, it is quite
certain that the characteristic smell of wine is
owing to an ether of an organic acid, resembling
one of the fatty acids.
It is only in liquids which contain other very
soluble acids, that the fatty acids and cenanthic
acid are capable of entering into combination with
the ether of alcohol, and of thus producing com-
pounds of a peculiar smell. This ether is found in
all wines which contain free acid, and is absent
from those in which no acids are present. This
acid, therefore, is the means by which the smell is
produced ; since without its presence cenanthic ether
could not be formed.
The greatest part of the oil of brandy made from
corn consists of a fatty acid not converted into
ether; it dissolves oxide of copper and metallic
oxides in general, and combines with the alkalies.
The principal constituent of this oil is an acid
identical in composition with cenanthic acid, but
different in properties. (Mulder.) It is formed in
u
290 VINOUS FERMENTATION.
fermenting liquids, which, if they be acid, contain
only acetic acid, a body which has no influence in
causing other acids to form ethers.
The oil of brandy made from potatoes is the
hydrate of an organic base analogous to ether, and
capable, therefore, of entering into combination
with acids. It is formed in considerable quantity
in fermenting liquids which are slightly alkaline,
under circumstances, consequently, in which it is
incapable of combining with an acid.
The products of the fermentation and putrefac-
tion of neutral vegetable and animal matters, are
generally accompanied by substances of an offensive
odour ; but the most remarkable example of the
generation of a true ethereal oil is seen in the fer-
mentation of the Herba centaurium minorius, a
plant which possesses no smell. When it is ex-
posed in water to a slightly elevated temperature
it ferments, and emits an agreeable penetrating
odour. By the distillation of the liquid, an ethereal
oily substance of great volatility is obtained, which
excites a pricking sensation in the eyes, and a flow
of tears. (Biichner.)
The leaves of the tobacco plant present the same
phenomena ; when fresh they possess very little or
no smell. When they are subjected to distillation
with water, a weak ammoniacal liquid is obtained^
upon which a white fatty crystallizable substance
swims, which does not contain nitrogen, and is quite
destitute of smell. But when the same plant, after
OILY AND ETHEREAL PRODUCTS. 291
being dried, is moistened with water, tied together
in small bundles, and placed in heaps, a peculiar
process of decomposition takes place. Fermentation
commences, and is accompanied by the absorption of
oxygen ; the leaves now become warm and emit the
characteristic smell of prepared tobacco and snuff.
When the fermentation is carefully promoted and
too high a heat avoided, this smell increases and
becomes more delicate ; and after the fermentation
is completed, an oily azotised volatile matter called
nicotine is found in the leaves. This substance —
nicotine, which possesses all the properties of a
base, was not present before the fermentation. The
different kinds of tobacco are distinguished from
one another, like wines, by having very different
odoriferous substances, which are generated along
with the nicotine.
We know that most of the blossoms and vegeta-
ble substances which possess a smell, owe this pro-
perty to a volatile oil existing in them ; but it is
not less certain, that others emit a smell only when
they undergo change or decomposition.
Arsenic and arsenious acid are both quite in-
odorous. It is only during their oxidation that they
emit their characteristic odour of garlic. The oil
of the berries of the elder-tree, many kinds of oil
of turpentine, and oil of lemons, possess a smell
only during their oxidation or decay. The same
is the case with many blossoms ; and Geiger has
u 2
292 VINOUS FERMENTATION.
shown, that the smell of musk is owing to its gra-
dual putrefaction and decay.
It is also probable, that the peculiar odorous
principle of many vegetable substances is newly
formed during the fermentation of the saccharine
juices of the plants. At all events, it is a fact,
that very small quantities of the blossoms of the
violet, elder, linden, or cowslip, added to a fer-
menting liquid, are sufficient to communicate a
very strong taste and smell, which the addition of
the water distilled from a quantity a hundred times
greater would not effect. The various kinds of beer
manufactured in Bavaria are distinguished by dif-
ferent flavours, which are given by allowing small
quantities of the herbs and blossoms of particular
plants to ferment along with the wort. On the
Rhine, also, an artificial bouquet is often given to
wine for fraudulent purposes, by the addition of
several species of the sage and rue to the ferment-
ing liquor ; but the perfume thus obtained differs
from the genuine aroma, by its inferior durability,
it being gradually dissipated.
The juice of grapes grown in different cli-
mates differs not only in the proportion of free
acid which it contains, but also in respect of the
quantity of sugar dissolved in it. The quantity of
azotised matter in the juice seems to be the same
in whatever part the grapes may grow; at least no
difference has been observed in the amount of
VARIOUS PROPERTIES OF WINES. 293
yeast formed during fermentation in the south of
France, and on the Rhine.
The grapes grown in hot climates, as well as the
boiled juice obtained from them, are proportionally
rich in sugar. Hence, during the fermentation of
the juice, the complete decomposition of its azo-
tised matters, and their separation in the insoluble
state, are effected before all the sugar has been
converted into alcohol and carbonic acid. A cer-
tain quantity of the sugar consequently remains
mixed with the wine in an m undecomposed state,
the condition necessary for its further decomposi-
tion being absent.
The azotised matters in the juice of grapes of
the temperate zones, on the contrary, are not com-
pletely separated in the insoluble state, when the
entire transformation of the sugar is effected. The
wine of these grapes, therefore, does not contain
sugar, but variable quantities of undecomposed
gluten in solution.
This gluten gives the wine the property of
becoming spontaneously converted into vinegar,
when the access of air is not prevented. For it
absorbs oxygen and becomes insoluble ; and its
oxidation is communicated to the alcohol, which is
converted into acetic acid.
By allowing the wine to remain at rest in casks
with a very limited access of air, and at the lowest
possible temperature, the oxidation of this azotised
294 FERMENTATION OF BEER.
matter is effected without the alcohol undergoing
the same change, a higher temperature being
necessary to enable alcohol to combine with oxygen.
As long as the wine in the stilling-casks deposits
yeast, it can still be caused to ferment by the addi-
tion of sugar, but old well-layed wine has lost this
property, because the condition necessary for fer-
mentation, namely, a substance in the act of decom-
position or putrefaction, is no longer present in it.
In hotels and other places .where the wine is
drawn gradually from, a cask, and a proportional
quantity of air necessarily introduced, its erema-
causis, that is, its conversion into acetic acid, is
prevented by the addition of a small quantity of sul-
phurous acid. This acid, by uniting itself with the
oxgyen of the air contained in the cask, or dis-
solved in the wine, prevents the oxidation of the
organic matter.
The various kinds of beer differ from one another
in the same way as the wines.
English, French, and most of the German beers,
are converted into vinegar when exposed to the
action of air. But this property is not possessed
by Bavarian beer, which may be kept in vessels only
half-filled without acidifying or experiencing any
change. This valuable quality is obtained for it
by a peculiar management of the fermentation of
the wort. The perfection of experimental know-
ledge has here led to the solution of one of the
THE BAVARIAN PROCESS. 295
most beautiful problems of the theory of fermen-
tation.
Wort is proportionally richer in gluten than in
sugar, so that during its fermentation in the com-
mon way, a great quantity of yeast is formed as a
thick scum. The carbonic acid evolved during the
process attaches itself to the particles of the yeast,
by which they become specifically lighter than the
liquid in which they are formed, and rise to its sur-
face. Gluten in the act of oxidation comes in con-
tact with the particles -of the decomposing sugar in
the interior of the liquid. The carbonic acid from
the sugar and insoluble ferment from the gluten
are disengaged simultaneously, and cohere together.
A great quantity of gluten remains dissolved in
the fermented liquid, even after the transformation
of the sugar is completed, and this gluten causes
the conversion of the alcohol into acetic acid, on
account of its strong disposition to attract oxygen,
and to undergo decay. Now, it is plain, that with
its separation, and that of all substances capable of
attracting oxygen, the beer would lose the property
of becoming acid. This end is completely attained
in the process of fermentation adopted in Bavaria.
The wort, after having been treated with hops in
the usual manner, is thrown into very wide flat
vessels, in which a large surface of the liquid is ex-
posed to the air. The fermentation is then allowed
to proceed while the temperature of the chambers
296 FERMENTATION OF BEER.
in which the vessels are placed,, is never allowed to
rise above from 45 to 50° F. The fermentation
lasts from three to six weeks, and the carbonic acid
evolved during its continuance is not in large
bubbles which burst upon the surface of the liquid,
but in small bubbles like those which escape from a
liquid saturated by high pressure. The surface of
the wort is scarcely covered with a scum, and all
the yeast is deposited on the bottom of the vessel
in the form of a viscous sediment.
In order to obtain a clear conception of the great
difference between the two kinds of fermentation,
it may perhaps be sufficient to recall to mind the
fact, that the transformation of gluten or other azo-
tised matters is a process consisting of several stages.
The first stage is the conversion of the gluten
into insoluble ferment in the interior of the liquid,
and as the transformation of the sugar goes on at
the same time, carbonic acid and yeast are simulta-
neously disengaged. It is known with certainty,
that this formation of yeast depends upon oxygen
being appropriated by the gluten in the act of
decomposition ; but it has "not been sufficiently
shown, whether this oxygen is derived from the
water, sugar, or from the gluten itself ; whether it
combines directly with the gluten, or merely with
its hydrogen, so as to form water. For the purpose
of obtaining a definite idea of the process, we may
designate the first change as the stage of oxidation.
THE BAVARIAN PROCESS. 29/
This oxidation of the gluten then, and the transpo-
sition of the atoms of the sugar into alcohol and
carbonic acid, are necessarily attendant on each
other, so that if the one is arrested the other must
also cease.
Now, the yeast which rises to the surface of the
liquid is not the product of a complete decomposi-
tion, but is oxidised gluten still capable of under-
going a new transformation by the transposition of
its constituent elements. By virtue of this condition
it has the power to excite fermentation in a solu-
tion of sugar ; and if gluten be also present, the de-
composing sugar induces its conversion into fresh
yeast, so that, in a certain sense, the yeast appears
to reproduce itself.
Yeast of this kind is oxidised gluten in a state of
putrefaction, and by virtue of this state it induces a
similar transformation in the elements of the sugar.
The yeast formed during the fermentation of
Bavarian beer is oxidised gluten in a state of decay.
The process of decomposition which its constituents
are suffering, gives rise to a very protracted putrefac-
tion (fermentation) in the sugar. The intensity of
the action is diminished in so great a degree, that
the gluten which the fluid still holds in solution
takes no part in it ; the sugar in fermentation does
not excite a similar state in the gluten.
But the contact of the already decaying and pre-
cipitated gluten or yeast, causes the eremacausis of
298 FERMENTATION OF BEER.
the gluten dissolved in the wort ; oxygen gas is
absorbed from the air, and all the gluten in solution
is deposited as yeast.
The ordinary frothy yeast may be removed from
fermenting beer by filtration, without the fermen-
tation being thereby arrested; but precipitated
yeast of Bavarian beer cannot be removed without
the whole process of its fermentation being inter-
rupted. The beer ceases to ferment altogether, or,
if the temperature is raised, undergoes the ordinary
fermentation.
The precipitated yeast does not excite ordinary
fermentation, and consequently is quite unfitted for
the purpose of baking, but the common frothy
yeast can cause the kind of fermentation by which
the former kind of yeast is produced.
When common yeast is added to wort at a tempera-
ture of between 40° and 45° F., a slow tranquil fer-
mentation takes place, and a matter is deposited on
the bottom of the vessel, which may be employed to
excite new fermentation ; and when the same oper-
ation is repeated several times in succession, the
ordinary fermentation changes into that process by
which only precipitated yeast is formed. The yeast
now deposited has lost the property of exciting
ordinary fermentation, but it produces the other
process even at a temperature of 50° F.
In wort subjected to fermentation, at a low tem-
perature, with this kind of yeast, the condition
THE BAVARIAN PROCESS. 299
necessary for the transformation of the sugar is
the presence of that yeast; but for the conver-
sion of gluten into ferment by a process of oxida-
tion, something more is required.
When the power of gluten to attract oxygen is
increased by contact with precipitated yeast in a
state of decay, the unrestrained access of air is the
only other condition necessary for its own conversion
into the same state of decay, that is for its oxida-
tion. We have already seen that the presence of
free oxygen and gluten are conditions which deter-
mine the eremacausis of alcohol and its conversion
into acetic acid, but they are incapable of exerting
this influence at low temperatures. A low temper-
ature retards the slow combustion of alcohol, while
the gluten combines spontaneously with the oxygen
of the air, just as sulphurous acid does when dis-
solved in water. Alcohol undergoes no such change
at low temperatures, but during the oxidation of the
gluten in contact with it, is in the same condition
as the gluten itself is placed in when sulphurous
acid is added to the wine in which it is contained.
The oxygen of the air unites both with the gluten
and alcohol of wine not treated with sulphurous
acid, but when this acid is present it combines
with neither of them, being altogether absorbed by
the acid. The same thing happens in the peculiar
process of fermentation adopted in Bavaria. The
oxygen of the air unites only with the gluten and
not with the alcohol, although it would have com-
300 FERMENTATION OF BEER.
bined with both at higher temperatures, so as to
form acetic acid.
Thus, then, this remarkable process of fermenta-
tion with the precipitation of a mucous-like ferment
consists of a simultaneous putrefaction and decay in
the same liquid. The sugar is in the state of
putrefaction, and the gluten in that of decay.
Apperfs method of preserving food, and this
kind of fermentation of beer, depend on the same
principle.
In the fermentation of beer after this manner,
all the substances capable of decay are separated
from it by means of an unrestrained access of air,
while the temperature is kept sufficiently low to
prevent the alcohol from combining with oxygen.
The removal of these substances diminishes the
tendency of the beer to become acescent, or in
other words, to suffer a further transformation.
In Apperfs mode of preserving food, oxygen is
allowed to enter into combination with the sub-
stance of the food, at a temperature at which
decay, but neither putrefaction nor fermentation,
can take place. With the subsequent exclusion
of the oxygen and the completion of the decay,
every cause which could effect further decomposi-
tion of the food is removed. The conditions for
putrefaction are rendered insufficient in both cases ;
in the one by the removal of the substances sus-
ceptible of decay, in the other by the exclusion of
the oxygen which would effect it.
THE BAVARIAN PROCESS. 301
It has been stated (page 296) to be uncertain,
whether gluten during its conversion into common
yeast, that is, into the insoluble state in which it
separates from fermenting liquids, really combines
directly with oxygen. If it does combine with
oxygen, then the difference between gluten and
ferment would be, that the latter would contain a
larger proportion of oxygen. Now it is very diffi-
cult to ascertain this, and even their analyses
cannot decide the question. Let us consider, for
example, the relations of alloxan and alloxantin to
one another. Both of these bodies contain the
same elements as gluten, although in different pro-
portions. Now they are known to be convertible
into each other, by oxygen being absorbed in the
one case, and in the other extracted. Both are
composed of absolutely the same elements, in equal
proportions ; with the single exception, that al-
loxantin contains 1 equivalent of hydrogen more
than alloxan.
When alloxantin is treated with chlorine and nitric
acid, it is converted into alloxan, into a body, there-
fore, which is alloxantin minus 1 equivalent of hydro-
gen. If on the other hand a stream of sulphuretted
hydrogen is conducted through alloxan, sulphur is
precipitated, and alloxantin produced. It may be
said, that in the first case hydrogen is abstracted,
in the other added. But it would be quite as
simple an explanation, if we considered them as
oxides of the same radical ; the1 alloxan being re-
302 FERMENTATION OF BEER.
garded as a combination of a body composed of
C8 N2 H2 O8 with 2 equivalents of water, and
alloxantin as a combination of 3 atoms of water,
with a compound consisting of C8 N2 H2 O7. The
conversion of alloxan into alloxantin would in this
case result from its eight atoms of oxygen being
reduced to seven, while alloxan would be formed
out of alloxantin, by its combining with an addi-
tional atom of oxygen.
Now, oxides are known which combine with
water, and present the same phenomena as alloxan
and alloxantin. But no compounds of hydrogen
are known which form hydrates ; and custom, which
rejects all dissimilarity until the claim to peculiarity
is quite proved, leads us to prefer an opinion, for
which there is no further foundation than that of
analogy. The woad (Isatis tinctoria) and several
species of the Nerium contain a substance similar
in many respects to gluten, which is deposited as
indigo blue, when an aqueous infusion of the dried
leaves is exposed to the action of the air. Now it
is very doubtful whether the blue insoluble indigo
is an oxide of the colourless soluble indigo, or the
latter a combination of hydrogen with the indigo
blue. Dumas has found the same elements in both,
except that the soluble compound contained 1 equi-
valent of hydrogen more than the blue.
In the same manner the soluble gluten may be
considered a compound of hydrogen, which becomes
ferment by losing a certain quantity of this ele-
THE BAVARIAN PROCESS. 303
ment when exposed to the action of the oxygen of
the air under favourable circumstances. At all
events, it is certain that oxygen is the cause of the
insoluble condition of gluten ; for yeast is not de-
posited on keeping wine, or during the fermen-
tation of Bavarian beer, unless oxygen has access
to the fluid.
Now whatever be the form in which the oxygen
unites with the gluten — whether it combines di-
rectly with it or extracts a portion of its hydrogen,
forming water — the products formed in the interior
of the liquid, in consequence of the conversion of
the gluten into ferment, will still be the same. Let
us suppose that gluten is a compound of another
substance with hydrogen, then this hydrogen must
be removed during the ordinary fermentation of
must and wort, by combining with oxygen, exactly
as in the conversion of alcohol into aldehyd by
eremacausis.
In both cases the atmosphere is excluded ; the
oxygen cannot, then, be derived from the air, nei-
ther can it be supplied by the elements of water,
for it is impossible to suppose that the oxygen will
separate from the hydrogen of water, for the pur-
pose of uniting with the hydrogen of gluten, in
order again to form water. The oxygen must,
therefore, be obtained from the elements of sugar,
a portion of which substance must, in order to
the formation of ferment, undergo a different de-
composition from that which produces alcohol.
304 FERMENTATION OF BEER.
Hence a certain part of the sugar will not be
converted into carbonic acid and alcohol, but will
yield other products containing less oxygen than
sugar itself contains. These products, as has
already been mentioned, are the cause of the great
difference in the qualities of fermented liquids,
and particularly in the quantity of alcohol which
they contain.
Must and wort do not, therefore, in ordinary fer-
mentation, yield alcohol in proportion to the quan-
tity of sugar which they hold in solution, a part of the
sugar being employed in the conversion of gluten
into ferment, and not in the formation of alcohol.
But in the fermentation of Bavarian beer all the
sugar is expended in the production of alcohol ;
and this is especially the case whenever the trans-
formation of the sugar is not accompanied by the
formation of yeast.
It is quite certain that in the distilleries of
brandy from potatoes, where no yeast is formed, or
only a quantity corresponding to the malt which
has been added, the proportion of alcohol and car-
bonic acid obtained during the fermentation of the
mash corresponds exactly to that of the carbon
contained in the starch. It is also known that the
volume of carbonic acid evolved during the fermen-
tation of beet-roots gives no exact indication of the
proportion of sugar contained in them, for less
carbonic acid is obtained than the same quantity of
pure sugar would yield.
THE BAVARIAN PROCESS. 305
Beer obtained by the mode of fermentation
adopted in Bavaria contains more alcohol, and pos-
sesses more intoxicating properties, than that made
by the ordinary method of fermentation, when the
quantities of malt used are the same. The strong
taste of the former beer is generally ascribed to its
containing carbonic acid in larger quantity, and
in a state of more intimate combination ; but this
opinion is erroneous. Both kinds of beer are, at
the conclusion of the fermentation, completely satu-
rated with carbonic acid, the one as much as the
other. Like all other liquids, they must both retain
such a portion of the carbonic acid evolved as
corresponds to their power of solution, that is, to
their volumes.
The temperature of the fluid during fermenta-
tion has a very important influence on the quantity
of alcohol generated. It has been mentioned, that
the juice of beet-roots allowed to ferment at from
86° to 95° (30° to 35° C.) yield no alcohol ; and that
afterwards, in the place of the sugar, mannite, a
substance incapable of fermentation, and contain-
ing very little oxygen, is found, together with lactic
acid and mucilage. The formation of these pro-
ducts diminishes in proportion as the temperature
is lower. But in vegetable juices, containing nitro-
gen, it is impossible to fix a limit, where the trans-
formation of the sugar is undisturbed by any other
process of decomposition.
It is known that in the fermentation of Bavarian
306 FERMENTATION OF BEER.
beer the action of the oxygen of the air, and the
low temperature, cause complete transformation of
the sugar into alcohol ; the cause which would pre-
vent that result, namely, the extraction of the
oxygen of part of the sugar by the gluten, in its
conversion into ferment, being avoided by the in-
troduction of oxygen from without.
The quantity of matters in the act of transfor-
mation is naturally greatest at the beginning of the
fermentation of must and wort ; and all the phe-
nomena which accompany the process, such as evo-
lution of gas, and heat, are best observed at that
time. These signs of the changes proceeding in
the fluid dimmish when the greater part of the
sugar has undergone decomposition ; but they must
cease entirely before the process can be regarded
as completed.
The less rapid process of decomposition which
succeds the violent evolution of gas, continues in
wine and beer until the sugar has completely dis-
appeared ; and hence it is observed, that the spe-
cific gravity of the liquid diminishes during many
months. This slow fermentation, in most cases,
resembles the fermentation of Bavarian beer, the
transformation of the dissolved sugar being in part
the result of a slow and continued decomposition of
the precipitated yeast ; but a complete separation
of the azotised substances dissolved in it cannot
take place when air is excluded.
The great influence which a rational manage-
THE BAVARIAN PROCESS. 307
ment of fermentation exercises upon the quality of
beer is well known in several of the German states.
In the grand-duchy of Hesse, for example, a con-
siderable premium is offered for the preparation of
beer, according to the Bavarian method ; and the
premium is to be adjudged to any one who can
prove that the beer brewed by him has lain for six
months in the store-vats without becoming acid.
Hundreds of casks of beer became changed to
vinegar before an empirical knowledge of those
conditions was obtained, the influence of which is
rendered intelligible by the theory.
Neither alcohol alone, nor hops, nor indeed both
together, preserve beer from becoming acid. The
better kinds of ale and porter in England are pro-
tected from acidity, but at the loss of the interest
of an immense capital. They are placed in large
closed wooden vessels, the surfaces of which are
covered with sand. In these they are allowed to
lie for several years, so that they are treated in a
manner exactly similar to wine during its ripening.
A gentle diffusion of air takes place through the
pores of the wood, but the quantity of azotised
substances being very great in proportion to the
oxygen which enters, they consume it, and prevent
its union with the alcohol. But the beer treated
in this way does not keep for two months without
acidifying, if it be placed in smaller vessels, to
which free access of the air is permitted.
x2
308 DECAY
DECAY OF WOODY FIBRE.
The conversion of woody fibre into the sub-
stances termed humus and mould is, on account
of its influence on vegetation, one of the most re-
markable processes of decomposition which occur
in nature.
Decay is not less important in another point of
view ; for, by means of its influence on dead vege-
table matter, the oxygen which plants retained
during life is again restored to the atmosphere.
The decomposition of woody fibre is effected in
three forms, the results of which are different, so
that it is necessary to consider each separately.
The first takes place when it is in the moist con-
dition, and subject to free uninterrupted access of
air ; the second occurs when air is excluded ;
and the third when the wood is covered with water,
and in contact with putrefying organic matter.
It is known that woody fibre may be kept under
water, or in dry air, for thousands of years without
suffering any appreciable change ; but that when
brought into contact with air, in the moist condi-
tion it converts the oxygen surrounding it into the
same volume of carbonic acid, and is itself gradually
changed into a yellowish brown, or black matter,
of a loose texture.
According to the experiments of De Saussure,
240 parts of dry sawdust of oak wood convert 10
cubic inches of oxygen into the same quantity of
OF WOODY FIBRE. 309
carbonic acid, which contains 3 parts, by weight, of
carbon; while the weight of the sawdust is di-
minished by 15 parts. Hence 12 parts, by weight,
of water, are at the same time separated from the
elements of the wood.
It has already been mentioned, that pure woody
fibre contains carbon and the elements of water.
Humus, however, is not produced by the decay of
pure woody fibre, but by that of wood which con-
tains foreign soluble and insoluble organic sub-
stances, besides its essential constituent.
The relative proportion of the component ele-
ments are, on this account, different in oak wood
and in beech, and the composition of both of these
differs very much from woody fibre, which is the
same in all vegetables. The difference, however, is
so trivial, that it may be altogether neglected in
the consideration of the questions which will now
be brought under discussion ; besides, the quantity
of the foreign substances is not constant, but varies
according to the season of the year.
According to the careful analysis of Gay-Lussac
and Thenard, 100 parts of oak wood, dried at 212°
(100° C.), from which all soluble substances had
been extracted by means of water and alcohol, con-
tained 52*53 parts of carbon, and *47'47 parts of
hydrogen and oxygen, in the same proportion as
they are contained in water.
Now it has been mentioned that moist wood acts
in oxygen gas exactly as if its carbon combined
310 DECAY
directly with oxygen, and that the products of this
action are carbonic acid and humus.
If the action of the oxygen were confined to the
carbon of the wood, and if nothing but carbon were
removed from it, the remaining elements would ne-
cessarily be found in the humus, unchanged except
in the particular of being combined with less car-
bon. The final result of the action would therefore
be a complete disappearance of the carbon, whilst
nothing but the elements of water would remain.
But when decaying wood is subjected to exami-
nation in different stages of its decay, the remark-
able result is obtained, that the proportion of carbon
in the different products augments. Consequently,
if we did not take into consideration the evolution
of carbonic acid under the influence of the air, the
conversion of wood into humus might be viewed
as a removal of the elements of water from the
carbon.
The analysis of mouldered oak wood, which was
taken from the interior of the trunk of an oak, and
possessed a chocolate brown colour and the struc-
ture of wood, showed that 100 parts of it contained
53*36 parts of carbon and 46*44 parts of hydrogen
and oxygen in the same relative proportions as in
water. From an examination of mouldered wood
of a light brown colour, easily reducible to a fine
powder, and taken from another oak, it appeared
that it contained 56*21 1 carbon and 43*789 water.
These indisputable facts point out the similarity
OF WOODY FIBRE. 311
of the decay of wood, with the slow combustion or
oxidation of bodies which contain a large quantity
of hydrogen. Viewed as a kind of combustion, it
would indeed be a very extraordinary process, if the
carbon combined directly with the oxygen ; for it
would be a combustion in which the carbon of the
burning body augmented constantly, instead of di-
minishing. Hence it is evident that it is the hy-
drogen which is oxidised at the expense of the
oxygen of the air; while the carbonic acid is
formed from the elements of the wood. Carbon
never combines at common temperatures with oxy-
gen, so as to form carbonic acid.
In whatever stage of decay wood may be, its ele-
ments must always be capable of being represented
by their equivalent numbers.
The following formula illustrates this fact with
great clearness :
C36 H22'O22— oak wood, according to Gay-Lussac and Thenard.*
C35 H20 O20— humus from oak wood ( Meyer) .f
C34 HIS O18— „ „ (Dr. JVilT).%
It is evident from these numbers that for every
two equivalents of hydrogen which is oxidised, two
atoms of oxygen and one of carbon are set free.
Under ordinary circumstances, woody fibre re-
quires a very long time for its decay ; but this pro-
cess is of course much accelerated by an elevated
* The calculation gives 52'5 carbon, and 47-5 water.
-}- The calculation gives 54 carbon and 46 water.
£ The calculation gives 56 carbon and 44 water.
312 DECAY
temperature and free unrestrained access of air.
The decay, on the contrary, is much retarded by
absence of moisture, and by the wood being sur-
rounded with an atmosphere of carbonic acid, which
prevents the access of air to the decaying matters.
Sulphurous acid, and all antiseptic substances,
arrest the decay of woody fibre. It is well known
that corrosive sublimate is employed for the purpose
of protecting the timber of ships from decay ; it
is a substance which completely deprives vegeta-
ble or animal matters, the most prone to decom-
position, of their property of entering into fermen-
tation, putrefaction, or decay.
But the decay of woody fibre is very much ac-
celerated by contact with alkalies or alkaline earths ;
for these enable substances to absorb oxygen, which
do not possess this power themselves ; alcohol (page
273), gallic acid, tannin, the vegetable colouring
matters (page 261), and several other substances,
are thus effected by them. Acids produce quite an
opposite effect ; they greatly retard decay.
Heavy soils, consisting of loam, retain longest
the most important condition for the decay of the
vegetable matter contained in it, viz., water ; but
their impermeable nature prevents contact with
the air.
In moist sandy soils, particularly such as are
composed of a mixture of sand and carbonate of
lime, decay proceeds very quickly, it being aided
by the presence of the slightly alkaline lime.
OF WOODY FIBRE. 313
Now let us consider the decay of woody fibre
during a very long period of time, and suppose
that its cause is the gradual removal of the hydro-
gen in the form of water, and the separation of its
oxygen in that of carbonic acid. It is evident that
if we subtract from the formula C36, H22, O22,
the 22 equivalents of oxygen, with 11 equivalents
of carbon, and 22 equivalents of hydrogen, which
are supposed to be oxidised by the oxygen of the
air, and separated in the form of water ; then from
1 atom of oak wood, 25 atoms of pure carbon will
remain as the final product of the decay. In other
words, 100 parts of oak, which contain 52*5 parts
of carbon, will leave as a residue 37 parts of car-
bon, which must remain unchanged, since carbon
does not combine with oxygen at common tempera-
tures.
But this final result is never attained in the de-
cay of wood under common circumstances ; and for
this reason, that with the increase of the proportion
of carbon in the residual humus, as in all decomposi-
tions of this kind, its attraction for the hydrogen,
which still remains in combination, also increases,
until at length the affinity of oxygen for the hydro-
gen is equalled, by that of the carbon for the
same element.
In proportion as the decay of woody fibre ad-
vances, its property of burning with flame, or in
other words, of developing carburetted hydrogen on
the application of heat, diminishes. Decayed wood
314 DECAY OF WOODY FIBRE.
burns without flame ; whence no other conclusion
can be drawn, than that the hydrogen, which an-
alysis shows to be present, is not contained in it
in the same form as in wood.
Decayed oak contains more carbon than fresh
wood, but its hydrogen and oxygen are in the same
proportion.
We would naturally expect that the flame given
out by decayed wood should be more brilliant, in
proportion to the increase of its carbon, but we
find, on the contrary, that it burns like tinder, ex-
actly as if no hydrogen were present. For the
purposes of fuel, decayed or diseased wood is of
little value, for it does not possess the property of
burning with flame, a property upon which the ad-
vantages of common wood depend. The hydro-
gen of decayed wood must consequently be sup-
posed to be in the state of water ; for had it any
other form, the characters we have described would
not be possessed by the decayed wood.
If we suppose decay to proceed in a liquid, which
contains both carbon and hydrogen, then a com-
pound containing still more carbon must be formed,
in a manner similar to the production of the crys-
talline colourless napthalin from a gaseous com-
pound of carbon and ^hydrogen. And if the com-
pound thus formed were itself to undergo further
decay, the final result must be the separation of
carbon in a crystalline form.
Science can point to no process capable of ac-
VEGETABLE MOULD. 315
counting for the origin and formation of diamonds,
except the process of decay. Diamonds cannot be
produced by the action of fire, for a high tempera-
ture, and the presence of oxygen gas, would call
into play their combustibility. But there is the
greatest reason to believe that they are formed in
the humid way, that is, in a liquid, and the process
of decay is the only cause to which then* formation
can with probability be ascribed.
Amber, fossil resin, and the acids in mellite, are
the products of vegetable matter which has suffered
decomposition. They are found in wood or brown
coal, and have evidently proceeded from the de-
composition of substances which were contained
in quite a different form in the living plants. They
are all distinguished by the proportionally small
quantity of hydrogen which they contain. The
acid from the mellite (mellitic acid) contains pre-
cisely the same proportions of carbon and oxygen
as that from amber (succinic acid) ; they differ only
in the proportion of their hydrogen. M. Bromeis*
found that succinic acid might be artificially formed
by the action of nitric acid on stearic acid, a true
process of eremacausis ; the experiment was made
in this laboratory (Giesseri).
VEGETABLE MOULD.
The term vegetable mould, in its general sig-
nification, is applied to a mixture of disintegrated
* Liebig's Annalen, Band xxxiv., heft 3.
316 VEGETABLE MOULD.
minerals, with the remains of animal and vegetable
substances. It may be considered as earth in
which humus is contained in a state of decomposi-
tion. Its action upon the air has been fully inves-
tigated by Ingenhouss and De Saussure.
When moist vegetable mould is placed in a ves-
sel full of air, it extracts the oxygen therefrom with
greater rapidity than decayed wood, and replaces
it by an equal volume of carbonic acid. When this
carbonic acid is removed and fresh air admitted,
the same action is repeated.
Cold water dissolves only To^rooth of its own
weight of vegetable mould ; and the residue left on
its evaporation consists of common salt with traces
of sulphate of potash and lime, and a minute quan-
tity of organic matter, for it is blackened when
heated to redness. Boiling water extracts several
substances from vegetable mould, and acquires a
yellow or yellowish brown colour, which is dissipated
by absorption of oxygen from the air, a black floc-
culent deposit being formed. When the coloured
solution is evaporated, a residue is left which be-
comes black on being heated to redness, and after-
wards yields carbonate of potash when treated with
water.
A solution of caustic potash becomes black when
placed in contact with vegetable mould, and the
addition of acetic acid to the coloured solution
causes no precipitate or turbidity. But dilute sul-
phuric acid throws down a light flocculent precipi-
MOULDERING OF VEGETABLE SUBSTANCES. 317
tate of a brown or black colour, from which the
acid can be removed with difficulty by means of
water. When this precipitate,, after having been
washed with water, is brought whilst still moist
under a receiver filled with oxygen, the gas is
absorbed with great rapidity ; and the same thing
takes place when the precipitate is dried in the air.
In the perfectly dry state it has entirely lost its
solubility in water, and even alkalies dissolve only
traces of it.
It is evident, therefore, that boiling water extracts
a matter from vegetable mould, which owes its solu-
bility to the presence of the alkaline salts contained
in the remains of plants. This substance is a
product of the incomplete decay of woody fibre.
Its composition is intermediate between woody fibre
and humus into which it is converted, by being
exposed in a moist condition to the action of the
air.
ON THE MOULDERING OF BODIES. — PAPER,
BROWN COAL, AND MINERAL COAL.
The decomposition of wood, woody fibre, and all
vegetable bodies when subjected to the action of
water, and excluded from the air, is termed moul-
dering.
Wood- or brown-coal and mineral coal, are the
remains of vegetables of a former world ; their
appearance and characters show, that they are pro-
318 DECOMPOSITION OF WOOD, COAL, ETC.
ducts of the processes of decomposition termed
decay and putrefaction. We can easily ascertain by
analysis the manner in which their constituents
have been changed, if we suppose the greater
part of their bulk to have been formed from woody
fibre.
But it is necessary before we can obtain a distinct
idea of the manner in which coal is formed, to con-
sider a peculiar change which woody fibre suffers
by means of moisture, when partially or entirely
excluded from the air.
It is known, that when pure woody fibre, as linen,
for example, is placed in contact with water, con-
siderable heat is evolved, and the substance is con-
verted into a soft friable mass which has lost all
coherence. This substance was employed in the
fabrication of paper before the use of chlorine,
as an agent for bleaching. The rags employed
for this purpose were placed in heaps, and it was
observed, that on their becoming warm a gas was
disengaged, and their weight diminished from 18
to 25 per cent.
When sawdust moistened with water is placed
in a closed vessel, carbonic acid gas is evolved in
the same manner as when air is admitted. A true
putrefaction takes place, the wood assumes a white
colour, loses its peculiar texture, and is converted
into a rotten friable matter.
The white decayed wood found in the interior
of trunks of dead trees which have been in
IN CONTACT WITH WATER. 319
contact with water, is produced in the way just
mentioned.
An analysis of wood of this kind, obtained from
the interior of the trunk of an oak, yielded, after
having been dried at 212°,
Carbon 47-11 . . 48'14
Hydrogen 6*31 . . 6'06
Oxygen 45-31 . . 44'43
Ashes 1-27 . . 1«37
100-00 100-00
Now, on comparing the proportions obtained
from these numbers with the composition of oak
wood, according to the analysis of Gay-Lussac and
Thenard, it is immediately perceived, that a certain
quantity of carbon has been separated from the
constituents of wood, whilst the hydrogen is, on the
contrary, increased. The numbers obtained by the
analysis correspond very nearly to the formula
C33 H27 O24. (The calculation from this formula
gives in 100 parts 47*9 carbon, 6'1 hydrogen, and
46 oxygen.)
The elements of water have, therefore, become
united with the wood, whilst carbonic acid is dis-
engaged by the absorption of a certain quantity of
oxygen.
If the elements of 5 atoms of water and ,3 atoms of
oxygen be added to the composition of the woody
fibre of the oak, and 3 'atoms of carbonic acid
deducted, the exact formula for white mouldered
wood is obtained.
320 DECOMPOSITION OF WOOD, COAL, ETC.
Wood C36 H22 O22
To this add 5 atoms of water , . . H 5 O 5
3 atoms of oxygen .... O 3
C36 H27 O30
Subtract from this 3 atoms Carbonic acid C 3 O 6
C33 H27 O24
The process of mouldering is, therefore, one of
putrefaction and decay, proceeding simultaneously,
in which the oxygen of the air and the component
parts of water take part. But the composition of
mouldered wood must change according as the
access of oxygen is more or less prevented. White
mouldered beech-wood yielded on analysis 47'67
carbon, 5*67 hydrogen, and 46*68 oxygen ; this
corresponds to the formula C33 H25 O24.
The decomposition of wood assumes, therefore,
two different forms, according as the access of the
air is free or restrained. In both cases carbonic acid
is generated; and in the latter case, a certain
quantity of water enters into chemical combination.
It is highly probable that in this putrefactive
process, as well as in all others, the oxygen of the
water assists in the formation of the carbonic acid.
Wood coal (brown coal of Werner) must have
been produced by a process of decomposition
similar to that of mouldering. But it is not easy to
obtain wood coal suited for analysis, for it is gene-
rally impregnated with resinous or earthy sub-
stances, by which the composition of those parts
which have been formed from woody fibre is essen-
tially changed.
PRODUCTION OF WOOD-COAL. 321
The wood coal which forms extensive layers
in the Wetterau (a district in Hesse Darmstadt.)
is distinguished from that found in other places, by
possessing the structure of wood unchanged, and by
containing no bituminous matter. This coal was
subjected to analysis, a piece being selected upon
which the annual circle could be counted. It was
obtained from the vicinity of Laubach ; 100 parts
contained
Carbon . -. 57-28
Hydrogen . . 6*03
Oxygen . . 36'10
Ashes . . 0-59
10000
The large amount of carbon, and small quan-
tity of oxygen, constitute the most obvious differ-
ence between this analysis and that of wood.
It is evident that the w^od which has undergone
the change into coal must have parted with a
certain portion of its oxygen. The proportion of
these numbers are expressed by the formula C33
H21 016. (The calculation gives 57*5 carbon and
5'98 hydrogen.)
When these numbers are compared with those
obtained by the analysis of oak, it would appear
that the brown coal was produced from woody
fibre by the separation of one equivalent of hydro-
gen, and the elements of three equivalents of car-
bonic acid.
322 CONVERTION OF WOOD
1 atom wood . . . C36 H22 O22
Minus 1 atom hydrogen and 3 atoms > r,0 TJ, ~-
arbonicacid > C3 Hl °6
WOOD COAL. C33 H2t O16 ;
All varieties of wood coal, from whatever strata
they may be taken, contain more hydrogen than
wood does, and less oxygen than is necessary to
form water with this hydrogen ; consequently they
must all be produced by the same process of decom-
position. The excess of hydrogen is either hydro-
gen of the wood which has remained in it unchanged,
or it is derived from some exterior source. The
analysis of wood coal from Ringkuhl, near Cassel,
where it is seldom found in pieces with the
structure of wood, gave, when dried at 2 1 2°,
Carbon 62'60 . . 63*83
Hydrogen 5 "02 • . 4*80
Oxygen 26*52 . . 25-51
Ashes 5-86 . 5.86
100-00 100-00
The proportions derived from these numbers cor-
respond very closely to the formula, C32 H 1 5 O9,
or they represent the constituents of wood, from
which the elements of carbonic acid, water, and 2
equivalents hydrogen have been separated.
C36 H22 O22 = Wood.
Subtract C4 H7 O13 zz: 4 atoms carbonic acid + 5 atoms of water
+ 2 atoms of hydrogen.
C82 HI5 O9 = Wood Coal from Ringkuhl.
INTO BROWN OR WOOD-COAL. 323
The formation of both these specimens of wood
coal appears from these formulae to have taken
place under circumstances which did not entirely
exclude the action of the air, and consequent oxi-
dation and removal of a certain quantity of hydro-
gen. Now the Laubacher coal is covered with a
layer of basalt, and the coal of Ringkuhl was taken
from the lowest seam of layers, which possess a
thickness of from 90 to 120 feet ; so that both may
be considered as well protected from the air.
During the formation of brown coal, the ele-
ments of carbonic acid have been separated from
the wood either alone, or at the same time with a
certain quantity of water. It is quite possible that
the difference in the process of decomposition may
depend upon the high temperature and pressure
under which the decomposition took place. At
least, a piece of wood assumed the character and
appearance of Laubacher coal, after being kept
for several weeks in the boiler of a steam engine,
and had then precisely the same composition. The
change in this case was effected in water, at a tem-
perature of from 334° to 352° F. ( 1 50°— 160° C.), and
under a corresponding pressure. The ashes of the
wood amounted to 0*5 1 per cent. ; a little less, there-
fore, than those of the Laubacher coal; but this must
be ascribed to the peculiar circumstances under
which it was formed. The ashes of plants exa-
mined by Berthier amounted always to much more
than this.
Y 2
324 CONVERSION OF WOOD
The peculiar process by which the decomposi-
tion of these extinct vegetables has been effected,
namely, a disengagement of carbonic acid from
their substance, appears still to go on at great
depths in all the layers of wood coal. At all events
it is remarkable that springs impregnated with
carbonic acid occur in many places, in the country
between Meissner, in the electorate of Hesse, and
the Eifel, which are known to possess large layers of
wood coal. These springs of, mineral water are
produced on the spot at which they are found ; the
springs of common water meeting with carbonic
acid during their ascent, and becoming impreg-
nated with it.
In the vicinity of the layers of wood coal at Salz-
hausen (Hesse Darmstadt) an excellent acidulous
spring of this kind existed a few years ago, and sup-
plied all the inhabitants of that district ; but it was
considered advantageous to surround the sides of
the spring with sandstone, and the consequence
was, that all the outlets to the carbonic acid were
closed, for this gas generally gains access to the
water from the sides of the spring. From that
time to the present this valuable mineral water has
disappeared, and in its place is found a spring of
common water.
Springs of water impregnated with carbonic
acid occur at Schwalheim, at a very short distance
from the layers of wood coal at Dorheim. M. Wil-
helmi observed some time since, that they are
INTO BROWN OR WOOD-COAL. 325
formed of common spring water which ascends
from below, and of carbonic acid which issues from
the sides of the spring. The same fact has been
shown to be the case in the famed Fachinger
spring, by M. Schapper.
The carbonic acid gas from the springs in the
Eifel is, according to Bischof, seldom mixed with
nitrogen or oxygen, and is probably produced in
a manner similar to that just described. At any
rate the air does not appear to take any part in
the formation of these acidulous springs. Their
carbonic acid has evidently not been formed either
by a combustion at high or low temperatures ;
for if it were so, the gas resulting from the com-
bustion would necessarily be mixed with f of
nitrogen, but it does not contain a trace of this
element. The bubbles of gas which escape from
these springs are absorbed by caustic potash, with
the exception of a residuum too small to be appre-
ciated.
The wood coal of Dorheim and Salzhausen must
have been formed in the same way as that of the
neighbouring village of Laubach ; and since the
latter contains the exact elements of woody fibre,
minus a certain quantity of carbonic acid, its com-
position indicates very plainly the manner in which
it has been produced.
The coal of the upper bed is subjected to an in-
cessant decay by the action of the air, by means
326 CONVERSION OF WOOD
of which its hydrogen is removed in the same
manner as in the decay of wood. This is recognised
by the way in which it burns, and by the formation
of carbonic acid in the mines.
The gases which are formed in mines of wood-
coal, and cause danger in their working, are not
combustible or inflammable as in mines of mineral
coal ; but they consist generally of carbonic acid
gas, and are very seldom intermixed with combus-
tible gases.
Wood-coal from the middle bed of the strata at
Ringkuhl gave on analysis 65*40 - 64'01 carbon
and 4*75 — 4*76 * hydrogen ; the proportion of
carbon here is the same as in specimens procured
from greater depths, but that of the hydrogen is
much less.
Wood and mineral coal are always accompanied by
iron pyrites (sulphuret of iron) or zinc blende
(sulphuret of zinc); which minerals are still formed
from salts of sulphuric acid, with iron or zinc,
during the putrefaction of all vegetable matter. It
is possible that the oxygen of the sulphates in
the layers of wood-coal is the means by which the
removal of the hydrogen is effected, since wood-
coal contains less of this element than wood.
According to the analysis of Richardson and
* The analysis of brown coal from Ringkuhl, as well as all those of the
same substance given in this work, have been executed in this laboratory
by M. Kuhnert of Cassel.
INTO MINERAL COAL. 327
Regnault, the composition of the combustible
materials in splint coal from Newcastle, and cannel
coal from Lancashire, is expressed by the formula
C24 H13 O. When this is com pared with the com-
position of woody fibre, it appears that these coals
are formed from its elements, by the removal
of a certain quantity of carburetted hydrogen
and carbonic acid in the form of combustible
oils. The composition of both of these coals is
obtained by the subtraction of 3 atoms of carbu-
retted hydrogen, 3 atoms of water, and 9 atoms of
carbonic acid from the formula of wood.
C36 H22 O22=: wood
3 atoms of carburetted hydrogen C3 H6
3 atoms of water . . H3 O3
9 atoms of carbonic acid C9 O18
Mineral coal
C12 H9 O21
O24 H13 O
Carburetted hydrogen generally accompanies all
mineral coal ; other varieties of coal contain volatile
oils which may be separated by distillation with
water. (Reichenbach.) The origin of naphtha is
owing to a similar process of decomposition. Cak-
ing coal from Caresfield, near Newcastle, contains
the elements of cannel coal, minus the consti-
tuents of olefiant gas C4 H4.
The inflammable gases which stream out of clefts
in the strata of mineral coal, or in rocks of the coal
formations, always contain carbonic acid, according
to a recent examination by Bischojf, and also car-
buretted hydrogen, nitrogen, and olefiant gas ; the
328 FORMATION OF COAL.
last of which had not been observed, until its exist-
ence in these gases was pointed out tyBischoff. The
analysis of fire-damp after it had been treated with
caustic potash showed its constituents to be,
Gas from an
abandoned Gerhard spas- Gas from a
mine near Sa8e near Lu~ mhie near
Wallesweiler. "enthal. Liekwege.
Vol. Vol. Vol.
Light carburetted hydrogen &/-S6 83-08 89-10
Olefiantgas 6-32 1-98 16-11
Nitrogen gas 2*32 14-1)4 4-79
100-00 ' 100-00 100-00
The evolution of these gases proves that changes
are constantly proceeding in the coal.
It is obvious from this, that a continual removal
of oxygen in the form of carbonic acid is effected
from layers of wood-coal, in consequence of which
the wood must approach gradually to the composi-
tion of mineral coal. Hydrogen, on the contrary,
is disengaged from the constituents of mineral coal
in the form of a compound of carbo -hydrogen ; a
complete removal of all the hydrogen would convert
coal into anthracite.
The formula C36 H22 O22, which is given for
wood, has been chosen as the empirical expression
of the analysis, for the purpose of bringing all the
transformations which woody fibre is capable of
undergoing under one common point of view.
Now, although the correctness of this formula
must be doubted, until we know with certainty the
true constitution of woody fibre, this cannot have
POISONS, CONTAGIONS, MIASMS. 329
the smallest influence on the account given of the.
changes to which woody fibre must necessarily be
subjected in order to be converted into wood or
mineral coal. The theoretical expression refers to
the quantity, the empirical merely to the relative
proportion in which the elements of a body are
united. Whatever form the first may assume, the
empirical expression must always remain un-
changed.
ON POISONS, CONTAGIONS, AND MIASMS.
A great many chemical compounds, some derived
from inorganic nature, and others formed in animals
and plants, produce peculiar changes or diseases in
the living animal organism. They destroy the vital
functions of individual organs ; and when their
action attains a certain degree of intensity, death is
the consequence.
The action of inorganic compounds, such as acids,
alkalies, metallic oxides, and salts, can in most cases
be easily explained. They either destroy the con-
tinuity of particular organs, or they enter into com-
bination with their substance. The action of sul-
phuric, muriatic, and oxalic acids, hydrate of
potash, and all those substances which produce the
direct destruction of the organs with which they
come into contact, may be compared to a piece
of iron, which can cause death by inflicting an
injury on particular organs, either when heated to
redness, or when in the form of a sharp knife.
330 POISONS, CONTAGIONS. MIASMS.
Such substances are not poisons in the limited
sense of the word, for their injurious action depends
merely upon their condition.
The action of the proper inorganic poisons is
owing, in most cases, to the formation of a chemical
compound by the union of the poison with the
constituents of the organ upon which it acts ; it is
owing to an exercise of a chemical affinity more
powerful than the vitality of the organ.
It is well to consider the action of inorganic
substances in general, in order to obtain a clear
conception of the mode of action of those which
are poisonous. We find that certain soluble com-
pounds, when presented to different parts of the
body, are absorbed by the blood, whence they are
again eliminated by the organs of secretion, either
in a changed or in an unchanged state.
Iodide of potassium, sulpho-cyanuret of potas-
sium, ferro-cyanuret of potassium, chlorate of pot-
ash, silicate of potash, and all salts with alkaline
bases, when administered internally to man and
animals in dilute solutions, or applied externally,
may be again detected in the blood, sweat, chyle,
gall, and splenic veins ; but all of them are finally
excreted from the body through the urinary pas-
sages.
Each of these substances, in its transit, produces
a peculiar disturbance in the organism — in other
words, they exercise a medicinal action upon it, but
they themselves suffer no decomposition. If any
EFFECTS OF SALTS ON THE ORGANISM. 331
of these substances enter into combination with
any part of the body, the union cannot be of a
permanent kind; for their re-appearance in the
urine shows that any compounds thus formed must
have been again decomposed by the vital processes.
Neutral citrates, acetates, and tartrates of the
alkalies, suffer change in their passage through the
organism. Their bases can indeed be detected in
the urine, but the acids have entirely disappeared,
and are replaced by carbonic acid which has united
with the bases. (Gilbert Blane and Wohler.)
The conversion of these salts of organic acids
into carbonates, indicates that a considerable quan-
tity of oxygen must have united with their ele-
ments. In order to convert 1 equivalent of acetate
of potash into the carbonate of the same base, 8
equivalents of oxygen must combine with it, of
which either 2 or 4 equivalents (according as an
acid or neutral salt is produced) remain in com-
bination with the alkali ; whilst the remaining 6 or
4 equivalents are disengaged as free carbonic acid.
There is no evidence presented by the organism
itself, to which these salts have been administered,
that any of its proper constituents have yielded so
great a quantity of oxygen as is necessary for their
conversion into carbonates. Their oxidation can,
therefore, only be ascribed to the oxygen of the
air.
During the passage of these salts through the
lungs, their acids take part in the peculiar process
332 POISONS, CONTAGIONS, MIASMS.
of eremacausis which proceeds in that organ ; a
certain quantity of the oxygen gas inspired unites
with their constituents, and converts their hydro-
gen into water, and their carbon into carbonic
acid. Part of this latter product (1 or 2 equiva-
lents) remains in combination with the alkaline
base, forming a salt which suffers no further change
by the process of oxidation ; and it is this salt
which is separated by the kidneys or liver.
It is manifest that the presence of these organic
salts in the blood must produce a change in the
process of respiration. A part of the oxygen in-
spired, which usually combines with the constitu-
ents of the blood, must, when they are present,
combine with their acids, and thus be prevented
from performing its usual office. The immediate
consequence of this must be the formation of ar-
terial blood in less quantity, or in other words, the
process of respiration must be retarded.
Neutral acetates, tartrates, and citrates placed
in contact with the air, and at the same time with
animal or vegetable bodies in a state of eremacausis,
produce exactly the same effects as we have de-
scribed them to produce in the lungs. They par-
ticipate in the process of decay, and are converted
into carbonates just as in the living body. If im-
pure solutions of these salts in water are left exposed
to the air for any length of time, their acids are
gradually decomposed, and at length entirely dis
appear.
EFFECTS OF SALTS ON THE ORGANISM. 333
Free mineral acids, or organic acids which are
not volatile, and salts of mineral acids with alka-
line bases, completely arrest decay when added to
decaying matter in sufficient quantity ; and when
their quantity is small, the process of decay is pro-
tracted and retarded. They produce in living
bodies the same phenomena as the neutral organic
salts, but their action depends upon a different
cause.
The absorption by the blood of a quantity of an
inorganic salt sufficient to arrest the process of
eremacausis in the lungs, is prevented by a very
remarkable property of all animal membranes,
skin, cellular tissue, muscular fibre, &c. ; namely,
by their incapability of being permeated by con-
centrated saline solutions. It is only when these
solutions are diluted to a certain degree with water
that they are absorbed by animal tissues.
A dry bladder remains more or less dry in satu-
rated solutions of common salt, nitre, ferro-cyanuret
of potassium, sulpho-cyanuret of potassium, sul-
phate of magnesia, chloride of potassium, and sul-
phate of soda. These solutions run off its surface
in the same manner as water runs from a plate of
glass besmeared with tallow.
Fresh flesh, over which salt has been strewed, is
found after 24 hours' swimming in brine, although
not a drop of water has been added. The water
has been yielded by muscular fibre itself, and having
334 POISONS, CONTAGIONS, MIASMS.
dissolved the salt in immediate contact with it, and
thereby lost the power of penetrating animal sub-
stances, it has on this account separated from the
flesh. The water still retained by the flesh con-
tains a proportionally small quantity of salt, having
that degree of dilution at which a saline fluid is
capable of penetrating animal substances.
This property of animal tissues is taken advan-
tage of in domestic economy for the purpose of re-
moving so much water from meat that a sufficient
quantity is not left to enable it to enter into pu-
trefaction.
In respect of this physical property of animal
tissues, alcohol resembles the inorganic salts. It
is incapable of moistening, that is, of penetrating
animal substances, and possesses such an affinity
for water as to extract it from moist substances.
When a solution of a salt, in a certain degree of
dilution, is introduced into the stomach, it is ab-
sorbed ; but a concentrated saline solution, in place
of being itself absorbed, extracts water from the
organ, and a violent thirst ensues. Some inter-
change of water and salt takes place in the stomach ;
the coats of this viscus yield water to the solution, a
part of which having previously become sufficiently
diluted, is, on the other hand, absorbed. But the
greater part of the concentrated solution of salt
remains unabsorbed, and is not removed by the
urinary passages ; it consequently enters the intes-
INORGANIC POISONS. 335
tines and intestinal canal, where it causes a dilution
of the solid substance deposited there, and thus
acts as a purgative.
Each of the salts just mentioned possess this
purgative action, which depends on a physical pro-
perty shared by all of them ; but besides this they
exercise a medicinal action, because every part of
the organism with which they come in contact
absorbs a certain quantity of them.
The composition of the salts has nothing to do
with their purgative action ; it is quite a matter of
indifference as far as the mere production of this
action is concerned (not as to its intensity), whether
the base be potash or soda, or in many cases lime
and magnesia; and whether the acid be phos-
phoric, sulphuric, nitric, or hydrochloric.
Besides these salts, the action of which does not
depend upon their power of entering into combi-
nation with the component parts of the organism ;
there is a large class of others which, when intro-
duced into the living body, effect changes of a very
different kind, and produce diseases or death, ac-
cording to the nature of these changes, without
effecting a visible lesion of any organs.
These are the true inorganic poisons, the action
of which depends upon their power of forming
permanent compounds with the substance of the
membranes, and muscular fibre.
Salts of lead, iron, bismuth, copper, and mer-
cury, belong to this class.
336 POISONS, CONTAGIONS, MIASMS.
When solutions of these salts are treated with a
sufficient quantity of albumen, milk, muscular
fibre, and animal membranes, they enter into com-
bination with those substances, and lose their own
solubility ; while the water in which they were dis-
solved loses all the salt which it contained.
The salts of alkaline bases extract water from
animal substances ; whilst the salts of the heavy
metallic oxides are, on the contrary, extracted from
the water, for they enter into combination with the
animal matters.
Now, when these substances are administered to
an animal, they lose their solubility by entering
into combination with the membranes, cellular
tissue, and muscular fibre ; but in very fewr
cases can they reach the blood. All experiments
instituted for the purpose of determining whether
they pass into the urine have failed to detect
them in that secretion. In fact, during their pas-
sage through the organism, they come into contact
with many substances by which they are retained.
The action of corrosive sublimate and arsenious
acid is very remarkable in this respect. It is
known that these substances possess, in an eminent
degree, the property of entering into combination
with all parts of animal and vegetable bodies, ren-
dering them at the same time insusceptible of
decay or putrefaction. Wood and cerebral sub-
stance are both bodies which undergo change with
great rapidity and facility when subject to the
INORGANIC POISONS. 33/
influence of air and water ; but if they are digested
for some time with arsenious acid or corrosive sub-
limate, they may subsequently be exposed to all the
influence of the atmosphere without altering in
colour or appearance.
It is further known that those parts of a body,
which come in contact with these substances during
poisoning, and which therefore enter into combi-
nation with them, do not afterwards putrefy ; so that
there can be no doubt regarding the cause of their
poisonous qualities.
It is obvious that if arsenious acid and corrosive
sublimate are not prevented by the vital principle
from entering into combination with the component
parts of the body, and consequently from rendering
them incapable of decay and putrefaction, they must
deprive the organs of the principal property which
appertains to their vital condition, viz. that of suf-
fering and effecting transformations ; or, in other
words, organic life must be destroyed. If the
poisoning is merely superficial, and the quantity of
the poison so small, that only individual parts of
the body which are capable of being regenerated
have entered into combination with it, then
eschars are produced — a phenomenon of a secondary
kind — the compounds of the dead tissues with the
poison being thrown off by the healthy parts. From
these considerations it may readily be inferred that
all internal signs of poisoning are variable and un-
certain ; for cases may happen, in which no apparent
z
338 POISONS, CONTAGIONS, MIASMS.
indication of change can be detected by simple
observations of the parts, because, as has been
already remarked, death may occur without the
destruction of any organs.
When arsenious acid is administered in solution,
it may enter into the blood. If a vein is exposed
and surrounded with a solution of this acid, every
blood-globule will combine with it, that is, will
become poisoned.
The compounds of arsenic, which have not the
property of entering into combination with the
tissues of the organism, are without influence on
life, even in large doses. Many insoluble basic
salts of arsenious acid are known not to be poison-
ous. The substance called alkargen, discovered by
Bunsen, which contains a very large quantity of
arsenic, and approaches very closely in composition
to the organic arsenious compounds found in the
body, has not the slightest injurious action upon
the organism.
These considerations enable us to fix with toler-
able certainty the limit at which the above sub-
stances cease to act as poisons. For since their
combination with organic matters must be regu-
lated by chemical laws, death will inevitably
result, when the organ in contact with the poison
finds sufficient of it to unite with atom for
atom ; whilst if the poison is present in smaller
quantity, a part of the organ will retain its vital
functions.
INORGANIC POISONS. 339
According to the experiments of Mulder* the
equivalent in which fibrin combines with muriatic
acid, and with the oxides of lead and copper, is ex-
pressed by the number 6361. It may be assumed
therefore approximatively, that a quantity of fibrin
corresponding to the number 6361 combines with
1 equivalent of arsenious acid, or 1 equivalent of
corrosive sublimate.
When 6361 parts of anhydrous fibrin are com-
bined with 30,000 parts of water, it is in the state
in which it is contained in muscular fibre or blood
in the human body. 100 grains of fibrin in this
condition would form a neutral compound of equal
equivalents with 3^0- grains of arsenious acid, and 5
grains of corrosive sublimate.
The atomic weight of the albumen of eggs and
of the blood deduced from the analysis of the com-
pound which it forms with oxide of silver is 7447,
and that of animal gelatin 5652.
100 grains of albumen containing all the water
with which it is combined in the living body, should
consequently combine with 1 \ grain of arsenious
acid.
These proportions, which may be considered as
the highest which can be adopted, indicate the
remarkably high atomic weights of animal sub-
stances, and at the same time teach us what very
small quantities of arsenious acid or corrosive subli-
mate are requisite to produce deadly effects.
* PoggendorfF's Annalen, Band xl. S. 259.
z 2
340 POISONS, CONTAGIONS, MIASMS.
All substances administered as antidotes in cases
of poisoning, act by destroying the power which
arsenious acid and corrosive sublimate possess, of
entering into combination with animal matters,
and of thus acting as poisons. Unfortunately no
other body surpasses them in that power, and the
compounds which they form can only be broken
up by affinities so energetic, that their action is as
injurious as that of the above-named poisons them-
selves. The duty of the physician consists, there-
fore, in his causing those parts of the poison which
may be free and still uncombined, to enter into
combination with some other body, so as to pro-
duce a compound incapable of being decomposed
or digested in the same conditions. Hydrated
peroxide of iron is an invaluable substance for this
purpose.
When the action of arsenious acid or corrosive
sublimate is confined to the surface of an organ,
those parts only are destroyed which enter into
combination with it ; an eschar is formed which is
gradually thrown off.
Soluble salts of silver would be quite as deadly
a poison as corrosive sublimate, did not a cause
exist in the human body by which their action is
prevented, unless their quantity is very great. This
cause is the presence of common salt in all animal
liquids. Nitrate of silver, it is well known, com-
bines with animal substances, in the same manner
as corrosive sublimate, and the compounds formed
INORGANIC POISONS. 341
by both; are exactly similar in the character of
being incapable of decay or putrefaction.
When nitrate of silver in a state of solution is ap-
plied to skin or muscular fibre, it combines with them
instantaneously ; animal substances dissolved in any
liquid are precipitated by it, and rendered insolu-
ble, or as it is usually termed — they are coagulated.
The compounds thus formed are colourless, and so
stable that they cannot be decomposed by other
powerful chemical agents. They are blackened
by exposure to light, like all other compounds
of silver, in consequence of a part of the oxide of
silver which they contain being reduced to the
metallic state. Parts of the body which have united
with salts of silver, no longer belong to the living
organism, for their vital functions have been ar-
rested by combination with oxide of silver ; and if
they are capable of being reproduced, the neigh-
bouring living structures throw them off in the
form of an eschar.
When nitrate of silver is introduced into the
stomach, it meets with common salt and free mu-
riatic acid ; and if its quantity is not too great, it
is immediately converted into chloride of silver — a
substance which is absolutely insoluble in pure
water. In a solution of salt or muriatic acid, how-
ever, chloride of silver does dissolve in extremely
minute quantity; and it is this small part which
exercises a medicinal influence when nitrate of sil-
ver is administered ; the remaining chloride of silver
342 POISONS, CONTAGIONS, MIASMS.
is eliminated from the body in the ordinary way.
Solubility is necessary to give efficacy to any sub-
stance in the human body.
The soluble salts of lead possess many properties
in common with the salts of silver and mercury ; but
all compounds of lead with organic matters are
capable of decomposition by dilute sulphuric acid.
The disease called painter's colic is unknown in all
manufactories of white lead in which the workmen
are accustomed to take as a preservative sulphuric
acid-lemonade (a solution of sugar rendered acid
by sulphuric acid).
The organic substances which have combined
in the living body with metallic oxides or metallic
salts, lose their property of imbibing water and re-
taining it, without at the same time being rendered
incapable of permitting liquids to penetrate through
their pores. A strong contraction and shrinking of
a surface is the general effect of contact with these
metallic bodies. But corrosive sublimate, and seve-
ral of the salts of lead, possess a peculiar property,
in addition to those already mentioned. When
they are present in excess, they dissolve the first
formed insoluble compounds, and thus produce an
effect quite the reverse of contraction, namely, a
softening of the part of the body on which they
have acted.
Salts of oxide of copper, even when in combina-
tion with the most powerful acids, are reduced by
many vegetable substances, particularly such as
ORGANIC POISONS. 343
sugar and honey, either into metallic copper, or
into the red suboxide, neither of which enters into
combination with animal matter. It is well known
that sugar has been long employed as the most
convenient antidote for poisoning by copper.
With respect to some other poisons, namely,
hydrocyanic acid and the organic bases strychnia
and brucia, we are acquainted with no facts calcu-
lated to elucidate the nature of their action. It
may, however, be presumed with much certainty,
that experiments upon their mode of action on
different animal substances, would very quickly
lead to the most satisfactory conclusions regarding
the cause of their poisonous effects.
There is a peculiar class of substances, which are
generated during certain processes of decomposi-
tion, and which act upon the animal economy as
deadly poisons, not on account of their power of
entering into combination with it, or by reason of
their containing a poisonous material, but solely by
virtue of their peculiar condition.
In order to attain to a clear conception of the
mode of action of these bodies, it is necessary to
call to mind the cause on which we have shown the
phenomena of fermentation, decay, and putrefaction,
to depend.
This cause may be expressed by the following
law, long since proposed by La Place and Berthollet,
although its truth with respect to chemical phe-
nomena has only lately been proved. " A molecule set
344 POISONS, CONTAGIONS^ MIASMS.
in motion by any power can impart its onm motion
to another molecule with which it may be in contact."
This is a law of dynamics, the operation of which
is manifest in all cases, in which the resistance
(force, affinity, or cohesion) opposed to the motion
is not sufficient to overcome it.
We have seen that ferment or yeast is a body in
the state of decomposition, the atoms of which,
consequently, are in a state of motion or transposi-
tion. Yeast placed in contact with sugar, com-
municates to the elements of that compound the
same state, in consequence of which, the consti-
tuents of the sugar arrange themselves into new and
simpler forms, namely, into alcohol and carbonic
acid. In these new compounds the elements are
united together by stronger affinities than they
were in the sugar, and therefore under the con-
ditions in which they were produced further de-
composition is arrested.
We know, also, that the elements of sugar assume
totally different arrangements, when the substances
which excite their transposition are in a different
state of decomposition from the yeast just men-
tioned. Thus, when sugar is acted on by rennet or
putrefying vegetable juices, it is not converted into
alcohol and carbonic acid, but into lactic acid,
mannite, and gum.
Again, it has been shown, that yeast added to a
solution of pure sugar gradually disappears, but that
when added to vegetable juices which contain gluten
ORGANIC POISONS. 345
as well as sugar, it is reproduced by the decompo-
sition of the former substance.
The yeast with which these liquids are made
to ferment, has itself been originally produced from
gluten.
The conversion of gluten into yeast in these
vegetable juices is dependent on the decomposition
(fermentation) of sugar ; for, when the sugar has
completely disappeared, any gluten which may still
remain in the liquid, does not suffer change from
contact with the newly-deposited yeast, but retains
all the characters of gluten.
Yeast is a product of the decomposition of gluten ;
but it passes into a second stage of decomposition
when in contact with water. On account of its
being in this state of further change, yeast excites
fermentation in a fresh solution of sugar, and if this
second saccharine fluid should contain gluten,
(should it be wort, for example,) yeast is again
generated in consequence of the transposition of the
elements of the sugar exciting a similar change in
this gluten.
After this explanation, the idea that yeast repro-
duces itself as seeds reproduce seeds, cannot for a
moment be entertained.
From the foregoing facts it follows, that a body
in the act of decomposition (it may be named the
exciter), added to a mixed fluid in which its consti-
tuents are contained, can reproduce itself in that
fluid, exactly in the same manner as new yeast is
346 POISONS, CONTAGIONS, MIASMS.
produced when yeast is added to liquids containing
gluten. This must be more certainly effected when
the liquid acted upon contains the body by the
metamorphosis of which the exciter has been
originally formed.
It is also obvious, that if the exciter be able to
impart its own state of transformation to one only
of the component parts of the mixed liquid acted
upon, its own reproduction may be the consequence
of the decomposition of this one body.
This law may be applied to organic substances
forming part of the animal organism. We know
that all the constituents of these substances are
formed from the blood, and that the blood by its
nature and constitution is one of the most complex
of all existing matters.
Nature has adapted the blood for the reproduc-
tion of every individual part of the organism ; its
principal character consists in its component parts
being subordinate to every attraction. These are
in a perpetual state of change or transformation,
which is effected in the most various ways through
the influence of the different organs.
The individual organs, such as the stomach,
cause all the organic substances conveyed to them
which are capable of transformation to assume new
forms. The stomach compels the elements of these
substances to unite into a compound fitted for the
formation of the blood. But the blood possesses
no power of causing transformations ; on the con-
PUTRID POISONS. 347
trary, its principal character consists in its readily
suffering transformations ; and no other matter can
be compared in this respect with it.
Now it is a well-known fact, that when blood,
cerebral substance, gall, pus, and other substances
in a state of putrefaction, are laid upon fresh
wounds ; vomiting, debility, and at length death, are
occasioned. It is also well known that bodies in
anatomical rooms frequently pass into a state of
decomposition which is capable of imparting itself
to the living body, the smallest cut with a knife
which has been used in their dissection producing
in these cases dangerous consequences.
The poison of bad sausages belongs to this class
of noxious substances.
Several hundred cases are known in which death
has occurred from the use of this kind of food.
In Wiirtemberg especially these cases are very
frequent, for there the sausages are prepared from
very various materials.
Blood, liver, bacon, brains, milk, meal and bread,
are mixed together with salt and spices ; the mix-
ture is then put into bladders or intestines, and
after being boiled is smoked.
When these sausages are well prepared they may
be preserved for months, and furnish a nourishing
savoury food ; but when the spices and salt are
deficient, and particularly when they are smoked
too late or not sufficiently, they undergo a peculiar
kind of putrefaction which begins at the centre of
348 POISONS, CONTAGIONS, MIASMS.
the sausage. Without any appreciable escape of
gas taking place they become paler in colour, and
more soft and greasy in those parts which have
undergone putrefaction, and they are found to
contain free lactic acid or lactate of ammonia ;
products which are universally formed during the
putrefaction of animal and vegetable matters.
The cause of the poisonous nature of these
sausages was ascribed at first to hydrocyanic acid,
and afterwards to sebacic acid, although neither of
these substances had been detected in them. But
sebacic acid is no more poisonous than ben zoic
acid, with which it has so many properties in com-
mon ; and the symptoms produced are sufficient to
show that hydrocyanic acid is not the poison.
The death which is the consequence of poisoning
by putrefied sausages succeeds very lingering and
remarkable symptoms. There is a gradual wasting
of muscular fibre, and of all the constituents of
the body similarly composed ; the patient becomes
much emaciated, dries to a complete mummy, and
finally dies. The carcase is stiff as if frozen, and is
not subject to putrefaction. During the progress
of the disease the saliva becomes viscous and ac-
quires an offensive smell.
Experiments have been made for the purpose of
ascertaining the presence of some matter in the
sausages to which their poisonous action could be
ascribed ; but no such matter has been detected.
Boiling water and alcohol completely destroy the
PUTRID POISONS. 349
poisonous properties of the sausages, without them-
selves acquiring similar properties.
Now this is the peculiar character of all sub-
stances which exert an action by virtue of their
existing condition — of those bodies the elements of
which are in the state of decomposition or trans-
position ; a state which is destroyed by boiling
water and alcohol without the cause of the influ-
ence being imparted to those liquids ; for a state of
action or power cannot be preserved in a liquid.
Sausages, in the state here described, exercise an
action upon the organism, in consequence of the
stomach and other parts with which they come in
contact not having the power to arrest their de-
composition ; and entering the blood in some way
or other, while still possessing their whole power,
they impart their peculiar action to the constituents
of that fluid.
The poisonous properties of decayed sausages
are not destroyed by the stomach as those of the
small-pox virus are. All the substances in the
body capable of putrefaction are gradually decom-
posed during the course of the disease, and after
death nothing remains except fat, tendons, bones,
and a few other substances which are incapable of
putrefying in the conditions afforded by the body.
It is impossible to mistake the modus operandi
of this poison, for Colin has clearly proved that
muscle, urine, cheese, cerebral substance, and other
matters, in a state of putrefaction, communicate
350 POISONS, CONTAGIONS, MIASMS.
their own state of decomposition to substances
much less prone to change of composition than the
blood. When placed in contact with a solution of
sugar, they cause its putrefaction, or the trans-
position of its elements into carbonic acid and
alcohol.
When putrefying muscle or pus is placed upon a
fresh wound, it occasions disease and death. It is
obvious that these substances communicate their
own state of putrefaction to the sound blood from
which they mere produced, exactly in the same
manner as gluten in a state of decay or putrefac-
tion causes a similar transformation in a solution of
sugar.
Poisons of this kind are even generated by the
body itself in particular diseases. In small-pox,
plague, and syphilis, substances of a peculiar nature
are formed from the constituents of the blood.
These matters are capable of inducing in the blood
of a healthy individual a decomposition similar to
that of which they themselves are the subjects ; in
other Words, they produce the same disease. The
morbid virus appears to reproduce itself just as
seeds appear to reproduce seeds.
The mode of action of a morbid virus exhibits
such a strong similarity to the action of yeast upon
liquids containing sugar and gluten, that the two
processes have been long since compared to one
another, although merely for the purpose of illus-
tration. But when the phenomena attending the
MORBID POISONS. 351
action of each respectively are considered more
closely, it will in reality be seen that their influence-
depends upon the same cause.
In dry air, and in the absence of moisture, all
these poisons remain for a long time unchanged ;
but when exposed to the air in the moist condition,
they lose very rapidly their peculiar properties.
In the former case, those conditions are afforded
which arrest their decomposition without destroying
it ; in the latter, all the circumstances necessary for
the completion of their decomposition are pre-
sented.
The temperature at which water boils, and contact
with alcohol, render such poisons inert. Acids,
salts of mercury, sulphurous acid, chlorine, iodine,
bromine, aromatic substances, volatile oils, and par-
ticularly empyreumatic oils, smoke, and a decoction
of coffee, completely destroy their contagious pro-
perties, in some cases combining with them or
otherwise effecting their decomposition. Now all
these agents, without exception, retard fermenta-
tion, putrefaction, and decay, and when present in
sufficient quantity, completely arrest these pro-
cesses of decomposition.
A peculiar matter to which the poisonous action
is due, cannot, we have seen, be extracted from
decayed sausages ; and it is equally impossible to
obtain such a principle from the virus of small-pox
or plague, and for this reason, that their peculiar
power is due to an active condition recognisable
352 POISONS, CONTAGIONS, MIASMS.
by our senses, only through the phenomena which
it produces.
In order to explain the effects of contagious mat-
ters, a peculiar principle of life has been ascribed
to them — a life similar to that possessed by the
germ of a seed, which enables it under favourable
conditions to develop and multiply itself. It would
be impossible to find a more correct figurative re-
presentation of these phenomena ; it is one which
is applicable to contagions, as well as to ferment?
to animal and vegetable substances in a state of
fermentation, putrefaction, or decay, and even to a
piece of decaying wood, which by mere contact
with fresh wood, causes the latter to undergo gra-
dually the same change and become decayed and
mouldered.
If the property possessed by a body of producing
such a change in any other substance as causes the
reproduction of itself, with all its properties, be
regarded as life, then, indeed, all the above pheno-
mena may be ascribed to life. But in that case
they must not be considered as the only processes
due to vitality, for the above interpretation of the
expression embraces the majority of the pheno-
mena which occur in organic chemistry. Life would,
according to that view, be admitted to exist in every
body in which chemical forces act.
If a body A, for example, oxamide (a substance
scarcely soluble in water, and without the slightest
taste), be brought into contact with another com-
MORBID POISONS. 353
pound B, which is to be reproduced ; and if this
second body be oxalic acid dissolved in water, then
the following changes are observed to take place : —
The oxamide is decomposed by the oxalic acid,
provided the conditions necessary for their exercis-
ing an action upon one another are present. The
elements of water unite with the constituents of
oxamide, and ammonia is one product formed, and
oxalic acid the other, both in exactly the proper
proportions to combine and form a neutral salt.
Here the contact of oxamide and oxalic acid in-
duces a transformation of the oxamide, which is de-
composed into oxalic acid and ammonia. The oxalic
acid thus formed, as well as that originally added,
are shared by the ammonia — or in other words, as
much free oxalic acid exists after the decomposi-
tion as before it, and is of course still possessed of
its original power. It matters not whether the free
oxalic acid is that originally added, or that newly
produced ; it is certain that it has been reproduced
in an equal quantity by the decomposition.
If we now add to the same mixture a fresh por-
tion of oxamide, exactly equal in quantity to that
first used, and treat it in the same manner, the
same decomposition is repeated ; the free oxalic
acid enters into combination, whilst another portion
is liberated. In this manner a very minute quan-
tity of oxalic acid may be made to effect the de-
composition of several hundred pounds of oxamide ;
A A
354 POISONS, CONTAGIONS, MIASMS.
and one grain of the acid to reproduce itself in
unlimited quantity.
We know that the contact of the virus of small-
pox causes such a change in the blood, as gives
rise to the reproduction of the poison from the
constituents of the fluid. This transformation is
not arrested until all the particles of the blood
which are susceptible of the decomposition have
undergone the metamorphosis. We have just seen
that the contact of oxalic acid with oxamide caused
the production of fresh oxalic acid, which in its
turn exercised the same action on a new portion
of oxamide. The transformation was only arrested
in consequence of the quantity of oxamide present
being limited. In their form both these transfor-
mations belong to the same class. But no one but
a person quite unaccustomed to view such changes
will ascribe them to a vital power, although we
admit they correspond remarkably to our common
conceptions of life ; they are really chemical pro-
cesses dependent upon the common chemical forces.
Our notion of life involves something more than
mere reproduction, namely, the idea of an active
power exercised ~by virtue of a definite form, and
production and generation in a definite form. By
chemical agency we can produce the constituents of
muscular fibre, skin, and hair ; but we can form by
their means no organised tissue, no organic cell.
The production of organs, the co-operation of a
THEIR MODE OF ACTION. 355
system of organs, and their power not only to
produce their component parts from the food pre-
sented to them, but to generate themselves in their
original form and with all their properties,, are cha-
racters belonging exclusively to organic life ; and
constitute a form of reproduction independent of
chemical powers.
The chemical forces are subject to the invisible
cause by which this form is produced. Of the
existence of this cause itself we are made aware
only by the phenomena which it produces. Its
laws must be investigated just as we investigate
those of the other powers which effect motion and
changes in matter.
The chemical forces are subordinate to this cause
of life, just as they are to electricity, heat, mecha-
nical motion and friction. By the influence of the
latter forces, they suffer changes in their direction,
an increase or diminution of their intensity, or a
complete cessation or reversal of their action.
Such an influence and no other is exercised by
the vital principle over the chemical forces ; but in
every case where combination or decomposition
takes place, chemical affinity and cohesion are in
action.
The vital principle is only known to us through
the peculiar form of its instruments, that is, through
the organs in which it resides. Hence, whatever
kind of energy a substance may possess, if it is
amorphous and destitute of organs from which the
A A2
356 POISONS, CONTAGIONS, MIASMS.
impulse, motion or change proceeds, it does not
live. Its energy depends in this case on a chemical
action. Light, heat, electricity, or other influences
may increase, diminish, or arrest this action, but
they are not its efficient cause.
In the same way the vital principle governs the
chemical powers in the living body. All those
substances to which we apply the general name of
food, and all the bodies formed from them in the
organism, are chemical compounds. The vital
principle has, therefore, no other resistance to over-
come, in order to convert these substances into
component parts of the organism, than the chemical
powers by which their constituents are held toge-
ther. If the food possessed life, not merely the
chemical forces, but this vitality, would offer resist-
ance to the vital force of the organism it nourished.
All substances adapted for assimilation are bodies
of a very complex constitution ; their atoms are
highly complex, and are held together only by a
weak chemical action. They are formed by the
union of two or more simpler compounds ; and in
proportion as the number of their atoms augments,
their disposition to enter into new combination is
diminished ; that is, they lose the power of acting
chemically upon other bodies.
Their complex nature, however, renders them
more liable to be changed, by the agency of exter-
nal causes, and thus to suffer decomposition. Any
external agency, in many cases even mechanical
THEIR MODE OF ACTION. 357
friction, is sufficient to cause a disturbance in the
equilibrium of the attraction of their constituents;
they arrange themselves either into new, more sim-
ple, and permanent combinations, or if a foreign
attraction exercise its influence upon it, they arrange
themselves in accordance with that attraction.
The special characters of food, that is of sub-
stances fitted for assimilation, are absence of active
chemical properties, and the capability of yielding
to transformations.
The equilibrium in the chemical attractions of
the constituents of the food is disturbed by the
vital principle, as we know it may be by many
other causes. But the union of its elements, so as
to produce new combinations and forms, indicates
the presence of a peculiar mode of attraction, and
the existence of a power distinct from all other
powers of nature, namely, the vital principle.
All bodies of simple composition possess a greater
or less disposition to form combinations. Thus
oxalic acid is one of the simplest of the organic
acids, while stearic acid is one of the most complex ;
and the former is the strongest, the latter one of
the weakest in respect to active chemical character.
By virtue of this disposition, simple compounds
produce changes in £very body which offers no
resistance to their action ; they enter into combi-
nation and cause decomposition.
The vital principle opposes to the continual
action of the atmosphere, moisture and tempera-
358 POISONS, CONTAGIONS, MIASMS.
ture upon the organism, a resistance which is, in a
certain degree, invincible. It is by the constant
neutralisation and renewal of these external influ-
ences that life and motion are maintained.
The greatest wonder in the living organism is the
fact that an unfathomable wisdom has made the
cause of a continual decomposition or destruction,
namely, the support of the process of respiration,
to be the means of renewing the organism, and of
resisting all the other atmospheric influences, such
as those of moisture and changes of temperature.
When a chemical compound of simple constitu-
tion is introduced into the stomach, or any other
part of the organism, it must exercise a chemical
action upon all substances with which it comes in
contact; for we know the peculiar character of
such a body to be an aptitude and power to enter
into combinations and effect decompositions.
The chemical action of such a compound is of
course opposed by the vital principle. The results
produced depend upon the strength of their
respective actions ; either an equilibrium of both
powers is attained, a change being effected without
the destruction of the vital principle, in which case
a medicinal effect is occasioned ; or the acting body
yields to the superior force of vitality, that is, it is
digested ; or lastly, the chemical action obtains the
ascendancy and acts as a poison.
Every substance may be considered as nutriment,
which loses its former properties when acted on by
THEIR MODE OF ACTION.. 359
the vital principle, and does not exercise a chemical
action upon the living organ.
Another class of bodies change the direction, the
strength, and intensity of the resisting force (the
vital principle), and thus exert a modifying influ-
ence upon the functions of its organs. They^.
produce a disturbance in the system, either by their
presence, and by themselves undergoing a change ;
these are medicaments.
A third class of compounds are called poisons,
when they possess the property of uniting with
organs or with their component parts, and when
their power of effecting this is stronger than the
resistance offered by the vital principle.
The quantity of a substance and its condition
must, obviously, completely change the mode of
its chemical action.
Increase of quantity is known to be equivalent to
superior affinity. Hence a medicine administered
in excessive quantity may act as a poison, and a
poison in small doses as a medicine.
Food will act as a poison, that is, it will produce
disease, when it is able to exercise a chemical action
by virtue of its quantity ; or, when either its con-
dition or its presence retards, prevents, or arrests
the motion of any organ.
A compound acts as a poison when all the parts
of an organ with which it is brought into contact
enter into chemical combination with it, while it
360 POISONS, CONTAGIONS, MIASMS.
may operate as a medicine, when it produces only
a partial change.
No other component part of the organism can be
compared to the blood, in respect of the feeble
resistance which it offers to exterior influences.
The blood is not an organ which is formed, but an
organ in the act of formation ; indeed, it is the sum
of all the organs which are being formed. The
chemical force and the vital principle hold each
other in such perfect equilibrium, that every dis-
turbance, however trifling, or from whatever cause
it may proceed, effects a change in the blood. This
liquid possesses so little of permanence, that it can-
not be removed from the body without immediately
suffering a change, and cannot come in contact
with any organ in the body, without yielding to its
attraction.
The slightest action of a chemical agent upon the
blood exercises an injurious influence ; even the
momentary contact with the air in the lungs,
although effected through the medium of cells and
membranes, alters the colour and other qualities of
the blood. Every chemical action propagates itself
through the mass of the blood ; for example, the
active chemical condition of the constituents of a
body undergoing decomposition, fermentation, pu-
trefaction, or decay, disturbs the equilibrium
between the chemical force and the vital principle
in the circulating fluid. The former obtains the
THEIR MODE OF ACTION. 361
preponderance. Numerous modifications in the
composition and condition of the compounds pro-
duced from the elements of the blood, result from
the conflict of the vital force with the chemical
affinity, in their incessant endeavour to overcome
one another.
All the characters of the phenomena of contagion
tend to disprove the existence of life in the conta-
gious matters. They without doubt exercise an
influence very similar to some processes in the
living organism ; but the cause of this influence is
chemical action, which is capable of being subdued
by other chemical actions, by opposed agencies.
Several of the poisons generated in the body by
disease lose all their power when introduced into
the stomach, but others are not thus destroyed.
It is a fact very decisive of their chemical nature
and mode of action, that those poisons which are
neutral or alkaline, such as the poisonous matter of
the contagious fever in cattle, (typhus contagiosus
ruminantium,) or that of the small-pox, lose their
whole power of contagion in the stomach ; whilst
that of sausages, which has an acid reaction, retains
all its frightful properties under the same circum-
stances.
In the former of these cases, the free acid present
in the stomach destroys the action of the poison,
the chemical properties of which are opposed to it ;
whilst in the latter it strengthens, or at all events
does not offer any impediment to poisonous action.
362 POISONS, CONTAGIONS, MIASMS.
Microscopical examination has detected peculiar
bodies resembling the globules of the blood in malig-
nant putrefying pus, in the matter of vaccine, &c.
The presence of these bodies has given weight to
the opinion, that contagion proceeds from the
development of a diseased organic life ; and these
formations have been regarded as the living seeds
of disease.
This view, which is not capable of discussion, has
led those philosophers who are accustomed to search
for explanations of phenomena in forms, to con-
sider the yeast produced by the fermentation of
beer as possessed of life. They have imagined it
to be composed of animals or plants, which nourish
themselves from the sugar in which they are placed,
and at the same time yield alcohol and carbonic
acid as excrementitious matters*.
It would perhaps appear wonderful if bodies,
possessing a crystalline structure and geometrical
figure, were formed during the processes of fermen-
tation and putrefaction from the organic substances
and tissues of organs. We know, on the contrary,
that the complete dissolution into inorganic com-
pounds is preceded by a series of transformations,
in which the organic structures gradually resign
their forms.
Blood, in a state of decomposition, may appear
to the eye unchanged ; and, when we recognise the
globules of blood in a liquid contagious matter, the
* Annalen der Pharmacie, Band xxix. S. 93 und 100.
THEIR MODE OF ACTION. 363
utmost that we can thence infer is, that those glo-
bules have taken no part in the process of decom-
position. All the phosphate of lime may be
removed from bones, leaving them transparent
and flexible like leather, without the form of the
bones being in the smallest degree lost. Again,
bones may be burned until they be quite white, and
consist merely of a skeleton of phosphate of lime,
but they will still possess their original form. In
the same way processes of decomposition in the
blood may affect individual constituents only of
that fluid, which will become destroyed and disap-
pear, whilst its other parts will maintain the original
form.
Several kinds of contagion are propagated through
the air : so that, according to the view already men-
tioned, we must ascribe life to a gas, that is, to an
aeriform body.
All the supposed proofs of the vitality of conta-
gions are merely ideas and figurative representa-
tions, fitted to render the phenomena more easy of
apprehension by our senses, with out explaining them.
These figurative expressions, with which we are so
willingly and easily satisfied in all sciences, are the
foes of all inquiries into the mysteries of nature ;
they are like the fata morgana, which show us
deceitful views of seas, fertile fields, and luscious
fruits, but leave us languishing when we have most
need of what they promise.
It is certain that the action of contagions is the
364 POISONS, CONTAGIONS, MIASMS,
result of a peculiar influence dependent on chemi-
cal forces, and in no way connected with the vital
principle. This influence is destroyed by chemical
actions, and manifests itself wherever it is not sub-
dued by some antagonist power. Its existence is
recognised in a connected series of changes and
transformations, in which it causes all substances
capable of undergoing similar changes to parti-
cipate.
An animal substance in the act of decomposition,
or a substance generated from the component parts
of a living body by disease, communicates its own
condition to all parts of the system capable of enter-
ing into the same state, if no cause exist in these
parts by which the change is counteracted or
destroyed.
Disease is excited by contagion.
The transformations produced by the disease
assumes a series of forms.
In order to obtain a clear conception of these
transformations, we may consider the changes which
substances, more simply composed than the living
body, suffer from the influence of similar causes.
When putrefying blood or yeast in the act of trans-
formation is placed in contact with a solution of
sugar, the elements of the latter substance are
transposed, so as to form alcohol and carbonic
acid.
A piece of the rennet-stomach of a calf in a state
of decomposition occasions the elements of sugar to
THEIR MODE OF ACTION. 365
assume a different arrangement. The sugar is con-
verted into lactic acid without the addition or loss of
any element. (1 atom of sugar of grapes C12 H12
O12 yields two atoms of lactic acid =2(C6 H6 O6.)
When the juice of onions or of beet-root is made
to ferment at high temperatures, lactic acid, man-
nite, and gum are formed. Thus, according to the
different states of the transposition of the elements
of the exciting body, the elements of the sugar
arrange themselves in different manners, that is,
different products are formed.
The immediate contact of the decomposing sub-
stance with the sugar, is the cause by which its
particles are made to assume new forms and
natures. The removal of that substance occasions
the cessation of the decomposition of the sugar, so
that should its transformation be completed before
the sugar, the latter can suffer no further change.
In none of these processes of decomposition is the
exciting body reproduced ; for the conditions neces-
sary to its reproduction do not exist in the elements
of the sugar.
Just as yeast, putrefying flesh, and the stomach
of a calf, in a state of decomposition, when intro-
duced into solutions of sugar, effect the transforma-
tion of this substance, without being themselves
regenerated ; in the same manner, miasms and
certain contagious matters produce diseases in the
human organism, by communicating the state of.
decomposition, of which they themselves are the
366 POISONS, CONTAGIONS, MIASMS.
subject, to certain parts of the organism, without
themselves being reproduced in their peculiar form
and nature during the progress of the decompo-
sition.
The disease in this case is not contagious.
Now when yeast is introduced into a mixed
liquid containing both sugar and gluten, such as
wort, the act of decomposition of the sugar effects
a change in the form and nature of the gluten,
which is, in consequence, also subjected to trans-
formation. As long as some of the fermenting sugar
remains, gluten continues to be separated as yeast,
and this new matter in its turn excites fermenta-
tion in a fresh solution of sugar or wort. If the
sugar, however, should be first decomposed, the
gluten which remains in solution is not converted
into yeast. We see, therefore, that the reproduc-
tion of the exciting body here depends —
1. Upon the presence of that substance from
which it was originally formed.
2. Upon the presence of a compound which is
capable of being decomposed by contact with the
exciting body.
If we express in the same terms the reproduction
of contagious matter in contagious diseases, since
it is quite certain that they must have their origin
in the blood, we must admit that the blood of a
healthy individual contains substances, by the de-
composition of which the exciting body or conta-
gion can be produced. It must further be admitted,
THEIR MODE OF ACTION. 367
when contagion results, that the blood contains a
second constituent capable of being decomposed by
the exciting body. It is only in consequence of the
conversion of the second constituent, that the
original exciting body can be reproduced.
A susceptibility of contagion indicates the pre-
sence of a certain quantity of this second body in
the blood of a healthy individual. The susceptibility
for the disease and its intensity, must augment ac-
cording to the quantity of that body present in the
blood; and in proportion to its diminution or disap-
pearance, the course of the disease will change.
When a quantity, however small, of contagious
matter, that is of the exciting body, is introduced
into the blood of a healthy individual, it will be
again generated in the blood, just as yeast is re-
produced from wort. Its condition of transformation
will be communicated to a constituent of the blood ;
and in consequence of the transformation suffered
by this substance, a body identical with or similar
to the exciting or contagious matter will be pro-
duced from another constituent substance of the
blood. The quantity of the exciting body newly
produced must constantly augment, if its further
transformation or decomposition proceeds more
slowly than that of the compound in the blood, the
decomposition of which it effects.
If the transformation of the yeast generated in
the fermentation of wort proceeded with the same
rapidity as that of the particles of the sugar con-
368 POISONS, CONTAGIONS, MIASMS.
tained in it, both would simultaneously disappear
when the fermentation was completed. But yeast
requires a much longer time for decomposition than
sugar, so that after the latter has completely disap-
peared, there remains a much larger quantity of
yeast than existed in the fluid at the commcement
of the fermentation, — yeast which is still in a state
of incessant progressive transformation, and there-
fore possessed of its peculiar property.
The state of change or decomposition which
affects one particle of blood, is imparted to a second,
a third, and at last to all the particles of blood in
the whole body. It is communicated in like man-
ner to the blood of another individual, to that of
a third person, and so on — or in other words, the
disease is excited in them also.
It is quite certain that a number of peculiar sub-
stances exist in the blood of some men and animals,
which are absent from the blood of others.
The blood of the same individual contains, in
childhood and youth, variable quantities of sub-
stances, which are absent from it in other stages of
growth. The susceptibility of contagion by peculiar
exciting bodies in childhood, indicates a propaga-
tion and regeneration of the exciting bodies, in
consequence of the transformation of certain sub-
stances which are present in the blood, and in the
absence of which no contagion could ensue. The
form of a disease is termed benignant, when the
transformations are perfected on constituents of the
THEIR MODE OF ACTION. 369
body which are not essential to life, without the
other, parts taking a share in the decomposition ; it
is termed malignant when they affect essential
organs.
It cannot be supposed that the different changes
in the blood, by which its constituents are con-
verted into fat, muscular fibre, substance of the
brain and nerves, bones, hair, &c., and the trans-
formation of food into blood, can take place without
the simultaneous formation of new compounds,
which require to be removed from the body by the
organs of excretion.
In an adult these excretions do not vary much
either in their nature or quantity. The food taken
is not employed in increasing the size of the body,
but merely for the purpose of replacing any sub-
stances which may be consumed by the various
actions in the organism ; every motion, every mani-
festation of organic properties, and every organic
action being attended by a change in the material
of the body, and by the assumption of a new form
by its constituents.*
But in a child this normal condition of suste-
nance is accompanied by an abnormal condition of
growth and increase in the size of the body, and of
* The experiments of Barruel upon the different odours emitted
from blood on the addition of sulphuric acid, prove that peculiar sub-
stances are contained in the blood of different individuals; the blood
of a man of a fair complexion and that of a man of dark complexion
were found to yield different odours ; the blood of animals also differed
in this respect very perceptibly from that of man.
B B
370 POISONS, CONTAGIONS, MIASMS.
each individual part of it. Hence there must be
a much larger quantity of foreign substances, not
belonging to the organism, diffused through every
part of the blood in the body of a young individual.
When the organs of secretion are in proper action,
these substances will be removed from the system ;
but when the functions of those organs are impeded,
they will remain in the blood or become accumu-
lated in particular parts of the body. The skin,
lungs, and other organs, assume the functions of
the diseased secreting organs, and the accumulated
substances are eliminated by them. If, when thus
exhaled, they happen to be in the state of progres-
sive transformation, these substances are conta-
gious, that is, they are able to produce the same
state of disease in another healthy organism, pro-
vided the latter organism is susceptible of their
action — or in other words, contains a matter cap-
able of suffering the same process of decomposi-
tion.*
The production of matters of this kind, which
render the body susceptible of contagion, may be
occasioned by the manner of living, or by the nu-
triment taken by an individual. A superabundance
of strong and otherwise wholesome food may pro-
duce them, as well as a deficiency of nutriment,
* Cold meat is always in a state of decomposition, that is, in a state
of eremacausis ; it is possible that this state may be communicated to
the system of a feeble individual, and may be one of the sources of
consumption.
THEIR MODE OF ACTION. 371
uncleanliness, or even the use of decayed substances
as food.
All these conditions for contagion must be con-
sidered as accidental. Their formation and accu-
mulation in the body may be prevented, and they
may even be removed from it without disturbing
its most important functions or health. Their
presence is not necessary to life.
The action, as well as the generation of the
matter of contagion is, according to this view, a
chemical process participated in by all substances
in the living body, and by all the constituents of
those organs in which the vital principle does not
overcome the chemical action. The contagion, ac-
cordingly, either spreads itself over every part of
the body, or is confined particularly to certain or-
gans, that is, the disease attacks all the organs or
only a few of them, according to the feebleness or
intensity of their resistance.
In the abstract chemical sense, reproduction of
a contagion depends upon the presence of two
substances, one of which becomes completely de-
composed, but communicates its own state of trans-
formation to the second. The second substance
thus thrown into a state of decomposition is the
newly formed contagion.
The second substance must have been originally
a constituent of the blood : the first may be a
body accidentally present ; but it may also may be
a matter necessary to life. If both be constituents
B B 2
372 POISONS, CONTAGIONS, MIASMS.
indispensable for the support of the vital functions
of certain principal organs, death is the consequence
of their transformation. But if the absence of the
one substance which was a constituent of the blood
do not cause an immediate cessation of the func-
tions of the most important organs, if they continue
in their action, although in an abnormal condition,
convalescence ensues. In this case the products
of the transformations still existing in the blood are
used for assimilation, and at this period secretions
of a peculiar nature are produced.
When the constituent removed from the blood
is a product of an unnatural manner of living, or
when its formation takes place only at a certain
age, the susceptibility of contagion ceases upon its
disappearance.
The effects of vaccine matter indicate that an
accidental constituent of the blood is destroyed by
a peculiar process of decomposition, which does
not affect the other constituents of the circulating
fluid.
If the manner in which the precipitated yeast of
Bavarian beer acts (page 266) be called to mind,
the modus operandi of vaccine lymph can scarcely
be matter of doubt.
Both the kind of yeast here referred to and the
ordinary ferment are formed from gluten, just as
the vaccine virus and the matter of small-pox are
produced from the blood. Ordinary yeast and the
virus of human small-pox, however, effect a violent
THEIR MODE OF ACTION. 373
tumultuous transformation, the former in vegetable
juices, the latter in blood, in both of which fluids
respectively their constituents are contained, and
they are reproduced from these fluids with all their
characteristic properties. The precipitated yeast
of Bavarian beer on the other hand acts entirely
upon the sugar of the fermenting liquid and occa-
sions a very protracted decomposition of it, in
which the gluten which is also present takes no
part. But the air exercises an influence upon
the latter substance, and causes it to assume a
new form and nature, in consequence of which this
kind of yeast also is reproduced.
The action of the virus of cow-pox is analogous
to that of the low yeast ; it communicates its own
state of decomposition to a matter in the blood, and
from a second matter is itself regenerated, but by a
totally different mode of decomposition ; the pro-
duct possesses the mild form, and all the properties
of the lymph of cow-pox.
The susceptibility of infection by the virus of
human small-pox must cease after vaccination, for
the substance to the presence of which this sus-
ceptibility is owing has been removed from the
body by a peculiar process of decomposition artifi-
cially excited. But this substance may be again
generated in the same individual so that he may
again become liable to contagion, and a second or
a third vaccination will again remove the peculiar
substance from the system.
Chemical actions are propagated in no organs so
374 POISONS, CONTAGIONS, MIASMS.
easily as in the lungs, and it is well known that
diseases of the lungs are above all others frequent
and dangerous.
If it is assumed that chemical action and the
vital principle mutually balance each other in the
blood, it must further be supposed that the chemi-
cal powers will have a certain degree of preponde-
rance in the lungs, where the air and blood are in
immediate contact ; for these organs are fitted by
nature to favour chemical action ; they offer no
resistance to the changes experienced by the
venous blood.
The contact of air with venous blood is limited to
a very short period of time by the motion of the
heart, and any change beyond a determinate point
is, in a certain degree, prevented by the rapid
removal of the blood which has become arterialised.
Any disturbance in the functions of the heart, and
any chemical action from without, even though
weak, occasions a change in the process of respi-
ration. Solid substances also, such as dust from
vegetable, (meal,) animal, (wool,) and inorganic
bodies, act in the same way as they do in a satu-
rated solution of a salt in the act of crystallisation,
that is, they occasion a deposition of solid matters
from the blood, by which the action of the air upon
the latter is altered or prevented.
When gaseous and decomposing substances, or
those which exercise a chemical action, such as sul-
phuretted hydrogen and carbonic acid, obtain access
to the lungs, they meet with less resistance in this
THEIR MODE OF ACTION. 375
organ tnan in any other. The chemical process of
slow combustion in the lungs is accelerated by all
substances in a state of decay or putrefaction, by
ammonia and alkalies ; but it is retarded by empy-
reumatic substances, volatile oils, and acids.
Sulphuretted hydrogen produces immediate decom-
position of the blood, and sulphurous acid combines
with the substance of the tissues, the cells, and
membranes.
When the process of respiration is modified by
contact with a matter in the progress of decay,
when this matter communicates the state of decom-
position, of which it is the subject, to the blood,
disease is produced.
If the matter undergoing decomposition is the
product of a disease, it is called contagion ; but if it
is a product of the decay or putrefaction of animal
and vegetable substances, or if it acts by its chemi-
cal properties, (not by the state in which it is,) and
therefore enters into combination with parts of the
body, or causes their decomposition, it is termed
miasm.
Gaseous contagious matter is a miasm emitted from
blood, and capable of generating itself again in blood.
But miasm properly so called, causes disease
without being itself reproduced.
All the observations hitherto made upon gaseous
contagious matters prove, that they also are sub-
stances in a state of decomposition. When vessels
filled with ice are placed in air impregnated with
gaseous contagious matter, their outer surfaces
376 POISONS, CONTAGIONS, MIASMS.
become covered with water containing a certain
quantity of this matter in solution. This water
soon becomes turbid, and in common language
putrefies, or, to describe the change more correctly,
the state of decomposition of the dissolved conta-
gious matter is completed in the water.
All gases emitted from putrefying animal and
vegetable substances in processes of disease, gene-
rally possess a peculiar nauseous offensive smell, a
circumstance which, in most cases, proves the
presence of a body in a state of decomposition.
Smell itself may in many cases be considered as a
reaction of the nerves of smell, or as a resistance
offered by the vital powers to chemical action.
Many metals emit a peculiar odour when rubbed,
but this is the case with none of the precious
metals, — those which suffer no change when exposed
to air and moisture. Arsenic, phosphorus, musk,
the oils of linseed, lemons, turpentine, rue, and
peppermint, possess an odour only when they are
in the act of eremacausis (oxidation at common
temperatures).
The odour of gaseous contagious matters is owing
to the same cause ; but it is also generally accom-
panied by ammonia, which may be considered in
many cases as the means through which the con-
tagious matter receives a gaseous form, just as it
is the means of causing the smell of innumerable
substances of little volatility, and of many which
have no odour. (Robiquet.)*
* Ann. de Chim. et de Phys. XV. 27.
THEIR MODE OF ACTION. 377
Ammonia is very generally produced in cases of
disease ; it is always emitted in those in which con-
tagion is generated, and is an invariable product of
the decomposition of animal matter. The presence
of ammonia in the air of chambers in which diseased
patients lie, particularly of those afflicted with a
contagious disease, may be readily detected ; for
the moisture condensed by ice in the manner just
described, produces a white precipitate in a solution
of corrosive sublimate, just as a solution of am-
monia does. The ammoniacal salts also, which are
obtained by the evaporation of rain water after an
acid has been added, when treated with lime so as
to set free their ammonia, emit an odour most
closely resembling that of corpses, or the peculiar
smell of dunghills.
By evaporating acids in air containing gaseous
contagions, the ammonia is neutralised, and we
thus prevent further decomposition, and destroy the
power of the contagion, that is, its state of chemical
change. Muriatic and acetic acids, and in several
cases nitric acid, are to be preferred for this purpose
before all others. Chlorine also is a substance
which destroys ammonia and organic bodies with
much facility ; but it exerts such an injurious and
prejudicial influence upon the lungs, that it may be
classed amongst the most poisonous bodies known,
and should never be employed in places in which
men breathe.
Carbonic acid and sulphuretted hydrogen, which
378 POISONS, CONTAGIONS, MIASMS.
are frequently evolved from the earth in cellars,
mines, wells, sewers, and other places, are amongst
the most pernicious miasms. The former may he
removed from the air by alkalies ; the latter, by
burning sulphur (sulphurous acid), or by the
evaporation of nitric acid.
The characters of many organic compounds are
well worthy of the attention and study both of phy-
siologists and pathologists, more especially in rela-
tion to the mode of action of medicines and poisons.
Several of such compounds are known, which to
all appearance are quite indifferent substances, and
yet cannot be brought into contact with one
another in water without suffering a complete
transformation. All substances which thus suffer
a mutual decomposition, possess complex atoms ;
they belong to the highest order of chemical com-
pounds. For example, amygdalin, a constituent of
bitter almonds, is a perfectly neutral body, of a
slightly bitter taste, and very easily soluble in
water. But when it is introduced into a watery
solution of synaptas, (a constituent of sweet
almonds,) it disappears completely without the
disengagement of any gas, and the water is found to
contain free hydrocyanic acid, hydruret of benzule
(oil of bitter almonds), a peculiar acid and sugar,
all substances of which merely the elements existed
in the amygdalin. The same decomposition is ef-
fected when bitter almonds, which contain the
same white matter as the sweet, are rubbed into a
THEIR MODE OF ACTION. 379
powder and moistened with water. Hence it hap-
pens that bitter almonds pounded and digested in
alcohol, yield no oil of bitter almonds, containing
hydrocyanic acid, by distillation with water; for
the substance which occasions the formation of
those volatile substances, is dissolved by alcohol
without change, and is therefore extracted from the
pounded almonds. Pounded bitter almonds contain
no amygdalin, also, after having been moistened
with water, for that substance is completely decom-
posed when they are thus treated.
No volatile compounds can be detected by their
smell in the seeds of the Sinapis alba and S. nigra.
A fixed oil of a mild taste is obtained from them
by pressure, but no trace of a volatile substance.
If, however, the seeds are rubbed to a fine powder,
and subjected to distillation with water, a volatile
oil of a very pungent taste and smell passes over
along with the steam. But if, on the contrary, the
seeds are treated with alcohol previously to their
distillation with water, the residue does not yield a
volatile oil. The alcohol contains a crystalline
body called sinapin, and several other bodies.
These do not possess the characteristic pungency
of the oil, but it is by the contact of them with
water, and with the albuminous constituents of the
seeds, that the volatile oil is formed.
Thus bodies regarded as absolutely indifferent
in inorganic chemistry, on account of their pos-
sessing no prominent chemical characters, when
380 POISONS, CONTAGIONS, MIASMS.
placed in contact with one another, mutually de-
compose each other. Their constituents arrange
themselves in a peculiar manner, so as to form new
combinations ; a complex atom dividing into two or
more atoms of less complex constitution, in conse-
quence of a mere disturbance in the attraction of
their elements.
The white constituents of the almonds and mus-
tard which resemble coagulated albumen, must be
in a peculiar state in order to exert their action
upon amygdalin, and upon those constituents of
mustard from which the volatile pungent oil is
produced. If almonds, after being blanched and
pounded, are thrown into boiling water, or
treated with hot alcohol, with mineral acids, or
with salts of. mercury, their power to effect a
decomposition in amygdalin is completely des-
troyed. Synaptas is an azotised body which cannot
be preserved when dissolved in water. Its solu-
tion becomes rapidly turbid, deposits a white pre-
cipitate, and acquires the offensive smell of putre-
fying bodies.
It is exceedingly probable that the peculiar state
of transposition into which the elements of syna-
ptas are thrown when dissolved in water, may be
the cause of the decomposition of amygdalin, and
formation of the new products arising from it. The
action of synaptas in this respect is very similar to
that of rennet upon sugar.
Malt, and the germinating seeds of corn in
THEIR MODE OF ACTION. 381
general, contain a substance called diastase, which
is formed from the gluten contained in them, and
cannot be brought in contact with starch and
water, without effecting a change in the starch.
When bruised malt is strewed upon warm starch
made into a paste with water, the paste, after a few
minutes becomes quite liquid, and the water is
found to contain, in place of starch, a substance in
many respects similar to gum. But when more
malt is added and the heat longer continued, the
liquid acquires a sweet taste, and all the starch is
found to be converted into sugar of grapes.
The elements of diastase have at the same time
arranged themselves into new combinations.
The conversion of the starch contained in food
into sugar of grapes in diabetes indicates that
amongst the constituents of some one organ of the
body a substance or substances exist in a state of
chemical action, to which the vital principle of the
diseased organ opposes no resistance. The com-
ponent parts of the organ must suffer changes
simultaneously with the starch, so that the more
starch is furnished to it, the more energetic and
intense the disease must become ; while if only food
which is incapable of suffering such transformations
from the same cause is supplied, and the vital energy
is strengthened by stimulant remedies and strong
nourishment, the chemical action may finally be
subdued, or in other words, the disease cured.
The conversion of starch into sugar may also be
382 POISONS, CONTAGIONS, MIASMS.
effected by pure gluten, and by dilute mineral
acids.
From all the preceding facts, we see that very
various transpositions, and changes of composition
and properties, may be produced in complex organic
molecules, by every cause which occasions a dis-
turbance in the attraction of their elements.
When moist copper is exposed to air containing
carbonic acid, the contact of this acid increases the
affinity of the metal for the oxygen of the air in so
great a degree that they combine, and the surface
of the copper becomes covered with green car-
bonate of copper. Two bodies, which possess the
power of combining together, assume, however,
opposite electric conditions at the moment at which
they come in contact.
When copper is placed in contact with iron, a
peculiar electric condition is excited, in consequence
of which the property of the copper to unite with oxy-
gen is destroyed, and the metal remains quite bright.
When formate of ammonia is exposed to a tem-
perature of 388° F. (180° C.) the intensity and
direction of the chemical force undergo a change,
and the conditions under which the elements of
this compound are enabled to remain in the same
form cease to be present. The elements, therefore,
arrange themselves in a new form ; hydrocyanic
acid and water being the results of the change.
Mechanical motion, friction, or agitation, is suffi-
cient to cause a new disposition of the constituents
THEIR MODE OF ACTION. 383
of fulminating silver and mercury, that is, to effect
another arrangement of their elements, in conse-
quence of which, new compounds are formed.
We know that electricity and heat possess a de-
cided influence upon the exercise of chemical affi-
nity ; and that the attractions of substances for one
another are subordinate to numerous causes which
change the condition of these substances, by alter-
ing the direction of their attractions. In the same
manner, therefore, the exercise of chemical powers
in the living organism is dependent upon the vital
principle.
The power of elements to unite together, and to
form peculiar compounds, which are generated in
animals and vegetables, is chemical affinity; but
the cause by which they are prevented from arrang-
ing themselves according to the degrees of their
natural attractions — the cause, therefore, by which
they are made to assume their peculiar order and
form in the body, is the vital principle.
After the removal of the cause which forced their
union — that is, after the extinction of life — most
organic atoms retain their condition, form, and
nature, only by a vis inertitz ; for a great law of
nature proves that matter does not possess the
power of spontaneous action. A body in motion
loses its motion only when a resistance is opposed
to it ; and a body at rest cannot be put in motion
or into any action whatever, without the operation
of some exterior cause.
384 POISONS,, CONTAGIONS, MIASMS.
The same numerous causes which are opposed
to the formation of complex organic molecules,
under ordinary circumstances, occasion their de-
composition and transformations when the only
antagonist power, the vital principle, no longer
counteracts the influence of those causes. Contact
with air and the most feeble chemical action now
effect changes in the complex molecules ; even the
presence of any body the particles of which are
undergoing motion or transposition is often sufficient
to destroy their state of rest, and to disturb the
statical equilibrium in the attractions of their con-
stituent elements. An immediate consequence of
this is that they arrange themselves according to
the different degrees of their mutual attractions,
and that new compounds are formed in which che-
mical affinity has the ascendancy, and opposes any
further change, while the conditions under which
these compounds were formed remain unaltered.
385
ADDITION TO NOTE AT PAGE 17.
IF the atmosphere possessed, in its whole extent, the
same density as it does on the surface of the sea, it would
have a height of 24,555 Parisian feet; but it contains the
vapour of water, so that we may assume its height to be
one geographical mile = 22,843 Parisian feet. Now the
radius of the earth is equal to 860 geographical miles ;
hence the
Volume of the Atmosphere =9,307,500 cubic miles = cube of 210-4 miles.
Volume of Oxygen . . =1,954,578 cubic miles = cube of 125' miles.
Volume of Carbonic Acid = 3,862-7 cubic miles = cube of 15*7 miles.
The maximum of the carbonic acid contained in the
atmosphere has not here been adopted, but the mean, which
is equal to 0-000415.
A man daily consumes 45,000 cubic inches (Parisian).
A man yearly consumes 9505-2 cubic feet.
1000 million men yearly consume 9,505,200,000,000
cubic feet.
1 cubic mile is equal to 11,919,500,000,000 cubic feet.
Hence a thousand million men yearly consume 0 79745
cubic miles of oxygen. But the air is rendered incapable
of supporting the process of respiration, when the quantity
of its oxygen is decreased 12 per cent.; so that a thousand
million men would make the air unfit for respiration in a
million years. The consumption of oxygen by animals,
and by the process of combustion, is not introduced into
the calculation.
C C
386
TABLES
SHOWING THE PROPORTION BETWEEN THE HESSIAN AND
ENGLISH STANDARD OF WEIGHTS AND MEASURES.
As the numbers throughout the Work have been stated
in reference to some common measure, it has been thought
advisable not to state the English equivalents to the Hessian
numbers in the text, lest they should distract the attention
of the reader by being placed in decimals. The numbers
do not represent absolute quantities, but are merely intended
to denote a proportion to other numbers ; so that it is quite
indifferent in what standard of weights or measures they
are stated. In almost every case where the term " Hessian
pounds " are employed, the word " parts " may be substi-
tuted. For those, however, who wish to be acquainted
with the exact English quantities, a table is given below.
lib. English is equal to 0-9071 9 Ibs. Hessian; hence,
about one-tenth less than the latter.
2 Ibs. Hessian are equal to 2-20 Ibs. English.
3 ... 3-306
4 - - - 4-409
5 - 5-51
6 - - - - 6-61
7 - 7-716
8 - - - 8-818
9 - - 9-92
10 - - - 11-02
20 - - 22-04
30 - - - - 33-06
40 - - 44-09
50 - - - 55-11
60 - 66-12
70 - - 77-16
80 - - 88-18
90 - - 99-29
100 - 110-2
200 - - - 220-4
300 - - 230-6
400 - - 440-9
500 551-1
600 - - - 661-2
700 771-6
800 - - - - 881-8
900 992-9
1000 - - - - 1102-0
387
SQUARE FEET.
The Hessian acre is equal to 40,000 Hessian square feet,
or 26,917 English square feet ; 1 English square foot being
equal to 1*4864 Hessian. The following is a Table to save
the trouble of calculation. The Table is only stated to the
figure 10, but by removing the decimal point one or two
figures, the whole series given in the case of the pounds
will also be obtained.
2 Square Feet Hessian are equal to 1-345 Square Feet English.
3
4 -
5
6 -
7
8 -
9
10 -
2-011
2-691
3-363
4-036
4-709
5-382
6-054
- 6-727
CUBIC FEET.
One English cubic foot contains 1 '81218 of a Hessian
cubic foot; the Hessian and English cubic inch may be
considered as equal, one English cubic inch containing
1-048715 Hessian cubic inch.
1 cubic foot Hessian is equal to 0-551 cubic foot English.
2 feet
3
4
5
6
7
8
9
10
1-103
1-655
2-207
2-759
3-311
3-863
4.415
4-966
5-518
feet
THE END.
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