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Full text of "Organic chemistry in its applications to agriculture and physiology"

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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 

i8 9 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. 

9210 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 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 > =O il 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 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 i ts 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 f y . 

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 4550 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 P ar ^ 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 hay 5 
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 Filices 9 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 
SKO 4 . 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. (6877 F.), that a volume of car- 
bonic acid has been formed, which, at 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 cubic 4 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. 

T 2 



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 ; the 1 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 . . 137 

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, 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 Sa 8 e 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 few r 
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^ - 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 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. 



LONDON : 
BRAWIURY AND EVANS, PRINTKKS, \\HITBFRIARS. 



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