NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
Medical Officers of the Army of India.
In the second place we may cite the researches of Dr. Sidney Martin, F.R.S.,
(which are set forth in the most recent reports of the Medical Officer to the Local
Government Board), "on the growth of the Typhoid Bacillus in soil," and which,
although still in course, have resulted in the production of evidence that certain
soils, and notably cultivated garden soils, do under certain conditions provide a
favourable medium for the viability of the germ; he notes also that when the soil,
sown with the bacillus, had become so dry as to be reduced to fine powder, the
specific living contagium could be recovered therefrom. A series of experiments
made under more natural conditions by Dr. Robertson, M.O.H., Sheffield,* has
supplied evidence of equal importance as regards the persistence and viability of
the typhoid bacillus in ordinary soil.
We may include in this category the forcible evidence adduced by Dr.
Waldo in the Milroy lectures of 1900 of the relations between fæcally con
-taminated dust and the prevalence of epidemic diarrhœa, which may be read in
the light of Ballard's and Tompkyns' observations into the connexion between
certain soil conditions and the same disease, and with Klein's and Hewlett's
researches into the rôle and prevalence of the B. enteriditis sporogenes as
the exciting agent of diarrhœa and cholera nostras.†
B. Typhi in soil.
Dust and bowel
diseases.
Horton-Smith remarks, that "if we remember that the typhoid bacillus has
great power of resisting dessication, remaining alive, it may be, for over a year in
the dried condition (Schiller), it becomes easy to understand how bacilli eliminat
-ed from the body may later pass into the atmosphere in the form of dust."‡
In summing up the subject of enteric fever and soil pollution as based on the
reports made of special investigations into local outbreaks, the Medical Officer to
the Local Government Board expresses himself as follows (Report of 1898-99) :—
"The failure to make a further substantial reduction in the amount of disease and
death from this cause is likely to be owing to the maintenance in the localities in question,
of conditions which involve organic pollution of the soil, and this especially where the
means of excrement disposal known as the privy-midden system is maintained."
In the third place, we have to take account of the intimate relation that
exists between the soil and the water-supply sources, and of t he soil as the source
of air-borne, insect-borne and food-borne organisms.
As regards the ingress of micro-organisms from the upper layers of the soil
to the ground-water, much of course depends on the nature of the soil, on the
depth and range of the ground-water from the surface, and on the penetrative effects
of rainfall. The subject has not received the attention it calls for in India, and
* See "Lancet", "British Medical Journal" of September 1897.
† Medical Officer's Reports, L. G. B., for 1897-98 and 1898-99, and Trans. Jenner Institute of Preven
-tive Medicine, Vol. II, 1900.
‡ Goulstonian Lectures; "Lancet," March 24, 1900, page 826.
Pollution of water
-supplies.
Scientific Memoirs by
To a consideration of the practical measures thus indicated, a subsequent part
of this paper will be devoted. The whole tendency of the evidence adduced is to
incriminate the soil as the chief source of enteric fever and other bowel-complaints,
directly or indirectly, through the water and food supplies. A specifically polluted
soil is a constant source of danger to the inhabitants; a non-specifically polluted
soil is only one degree less dangerous as it provides a favorable medium for the
specific virus, and by its action on the individual it lowers the natural resistance to
that virus. The problem of removal and disposal involves above all thing an
avoidance of the pollution of the soil of the environment, at least so far as this
can reasonably be held to enter into direct relations with the community dwelling
thereon. It is necessary therefore, as a preliminary to the practical suggestions to
be made, to invite attention to the natural forces upon which we depend for the ulti-
mate mineralization of all waste organic matter, to the consideration of which the
writer was naturally led in the course of a series of experiments on the treatment
of the sewage of a large Indian community.
II.
One of the very first uses to which the first microscope was applied was the
discovery by van Leeuwenhoek of minute living forms in the intestinal canals
of frogs and birds, and in his own diarrhœal evacuations. This was a purely objec-
tive observation, the significance of which only ripened slowly during the next two
hundred years ; now we know that the richest hot-bed of bacteria in the animal
body is the intestine. With its alkalinity and its high and constant temperature,
putrefactive and fermentative organisms of all kinds, both aërobic and anaërobic,
find optimal conditions of existence. Escherich* has shown that in the interior
of the intestine, towards the centre of the mass that fills it, only anaerobic pro-
cesses can go on, but along the course of the walls in contact with the blood
vessels, aerobic changes can and do occur. According to the nature of the food
ingested we have a predominance of either putrefactive or fermentative changes
already set up in the alimentary canal, the first stages of those complex processes
of resolution to the ultimate forms in which Nitrogen and Carbon can re-enter the
cycle of life. The intestinal canal of the fœtus is sterile, but with the first food,
bacteria are conveyed to the intestine, an adaptation in small part to certain process-
es preparatory to assimilation, but chiefly to the ultimate resolution of the waste
products. But before we come to speak of bacterial action as specially directed
* " D i e D a r m b a k t e r i e n . "
126
Medical Officers of the Army of India.
127
to our artificial methods of sewage purification, it may be well to point out briefly
that the processes of assimilation and dissimilation in the human body, whether
we consider the specific actions of the cellular units and their ferments
or those of the normal bacterial flora of the intestinal tract, afford a clear indi--
cation of, and analogy to, the action of bacteria in our biological methods outside
the body. The elemental food substances which provide us with energy are
of precisely similar composition, if in varying proportions, to the waste organic
fluids and solids which go to make up "Sewage." The means employed and
the object are the same in both cases. In both there is a conversion of poten--
tial into kinetic energy, by the splitting up and rendering soluble of the complex
molecule (albuminous, carbohydrate or fatty) to permit of final oxidation, and
in both the agencies concerned utilize the energy obtained for their vital pur--
poses. And in the living body we see as a result the formation of end products,
in the gases and water formed and excreted by the chief emunctories, which
it is our object to arrive at by our artificial methods; but the human body can
only partially effect this dissolution, and there remains a residue of unattacked
and intermediate products, which constitute the solids and liquids of sewage
and of which the breaking-down is only partially initiated by the putrefactive
bacteria of the large intestine.* The natural agents then are present and
pass away with these remaining excretory products, and we have simply to
provide the former with the necessary conditions for their functions. Here we
have the indication of those natural methods, to which Pasteur by his
fundamental researches on fermentation supplied the key, and further, definitely
formulated the institutes of the modern technical applications of bacteriology of
which the "biological" method of the treatment of sewage is not the smallest
triumph.
It will therefore, in the first place, be no mere academic exercise to briefly
summarise our knowledge on these points; we may then deduce the first
principles which should guide us in practice, and this will lead to a brief con--
sideration of their application to the conditions which obtain, more especially in
Indian cantonments and bazaars.
All living matter is constantly undergoing decomposition, and hence must
assimilate substances that contain all the chemical elements of which it is con
-structed. In the complete drama of metabolism we find a series of acts rising by
synthesis to the most complex of known organic compounds, the proteids; and
conversely, a complementary series of processes of destruction of living substance
into its simplest inorganic compounds and elements. This drama is played upon
* See Bunge, "Physiological Chemistry," pages 304— 305, and Schäfer's "Text-book of Physiology," V
Pages 463-474.
The drama of
metabolism.
128
Scientific Memoirs by
Pasteur's work.
The rôle of oxy
-
gen.
the stage of every living organism, and although we cannot say of the vegetable
cell that it is concerned exclusively with synthetic functions, nor of the animal
cell that it maintains its vital energy solely by decomposition, yet we recognize
that, broadly, vegetable and animal mutually subserve each other's needs in the
rhythmical flow of energy which never varies in its final amount. Inasmuch
as the animal cell is unable to complete the resolution of the complex potential
compound into its final kinetic terms so as to be available for plant food, we need
a third kind of organism, half plant and half animal, to complete the cycle, and
whose metabolic relations are not so sharply differentiated as those of the higher
organised plants and animals. This link is supplied by the fungi, which
obtain their necessary Carbon and Nitrogen from more or less complex chemical
compounds, organic (and, for the most part, dead) and inorganic; they
thus subserve both plant and animal life, by rendering the food elements available,
and by the transmution of dangerous waste products. For this they are fitted by
the wide limits within which their external vital conditions can vary, and by their
rapid multiplication, for which they use up a large amount of material in a short
time, a small portion of which goes to provide for their own growth, while a
far larger proportion is decomposed by their fermentative actions and is thus
prepared for final oxidation. One of the first steps in our knowledge of their
physiology was the discovery by Pasteur that the yeast and mould fungi were, in
so far, like the higher plants, that they could assimilate their necessary Nitrogen
and Carbon from ammoniacal salts and even from nitrates, and thus these were
differentiated from the great class of fission fungi, which in their vital require
-
ments stand nearer to the animal organism. It was further shown by the same
observer that micro-organisms exhibited the most marked differences in their relation
to free oxygen which had been supposed to be a sine quâ non for all living beings
.
One great class requires free oxygen and leads to rapid oxidation of their medium,
while another can not only live without the free element, but can only fulfil their
proper functions in its absence, and that, given this condition, an extensive but
superficial decomposition of the nutrient material takes place, which represents
the fundamental dynamic phenomenon of fermentation. It is true that Pasteur's
dictum, "fermentation is life without oxygen," has, on account of later knowledge,
lost the force and truth of a universal law, and, moreover, we have learnt that the
majority of putrefactive organisms belong to the class of facultative anaërobes,
and that their vital functions vary in the presence or absence of free oxygen,*
much as the products of a smouldering kiln and a blast furnace vary. A microbe
that for its own vital advantage would better thrive in free oxygen, will, if
* See Duclaux, " Traite de Microbiologie," Tome I.
Medical Officers of the Army of India.
deprived thereof, produce a far more extensive, if not so profound, effect upon the
substratum from which it derives its vital energy. It is not therefore .that we have
to depend for an all-important process on a certain limited number of obligatory
anaërobes, but that we enlist the special faculty of the vast majority of aerobic
organisms by arranging to deprive them of a sufficiency of air for their "external"
respiratory needs. The integrity of the complex molecule is infringed by the
dislocation of its oxygen, which the aërobe will not be denied, and the combina--
tion of the atoms of the resulting products is rendered still more unstable.
We see how in the case of the alcoholic fermentation of sugar, the amount of
sugar decomposed in the unit of time is inversely proportional to the supply of
oxygen;* and Fränkel† has observed that the decomposition of albumen goes on
twice as fast in dogs when their supply of oxygen is diminished.
"The energy that all other plants and animals gain by respiration is
obtained by the fermentative organisms from a less complete disintegration of
the respirable substance, the relative smallness of the amount of energy set free
being compensated by the large quantity of substance decomposed. In other
words, the ordinary respiration is a complete combustion of a few molecules, that of
ferment organisms by deprivation of free oxygen, an incomplete combustion of
many molecules.‡ "But the products so formed are far more susceptible of oxidation
at a later stage than the original substances, and by division of labour, we derive
an enormous advantage in time and space.
While the building-up of the living-substance is brought about by several
groups of phenomena, which we can represent by the formulæ of polymerization,
anhydrosis and reduction by loss of oxygen, generally effected by the entry of
hydrogen into the molecule, so also the opposite processes of disintegration by
bacteria takes place by the loosening of the bands of polymerization, through
hydration and finally through oxidation. But while oxidation may indeed be
taken to represent the final stage, we cannot utilize it with our available
resources on substances of large molecular constitution, until the material
has been duly prepared and, as it were, "primed" for the explosion.§ No
amount of free oxygen in the first stage would avail; we see this in the
exposure of dead organic matter to the air, and we know that it would
not only inhibit the growth and functions of the true anaërobes, but it would
merely encourage the vegetative life processes of the aërobes, at the expense of
their fermentative faculty. Anaërobiosis then in the case of the great majority
of putrefactive organisms is necessary for fermentation, and acts as the chopper
to the log, or the poker to the fire, and is an essential preliminary to the work in
* Bunge, "Physiological and Pathological Chemistry," page 185.
†
V i r c h o w ' s
A r c h i v ,
V o l . L X V I I , p . 2
8 3 .
‡ F i s c h e r : " V o r l e s u n g e n ü b e r B a k t e r i e n . "
§ S e e p a g e 1
3 4 .
1 1
Specific vital ac
- t i o n s o f d i f f e r e n t o r -
ganisms.
Scientific Memoirs by
question. At the same time we recognize that another class of organisms
(obligatory aërobes) depend for their fermentative faculty on the presence of
more or less oxygen, as in the lactic and acetic fermentations ; and further, as
has already been noted, we recognise still another distinct class that not only
demand free oxygen in abundance, but require for the building up of their
albuminous molecule the simpler inorganic salts and compounds which have resulted
from previous decompositions. We can therefore no longer define the rôles of
these several classes by one simple formula ; there are a series of processes,
which require separate consideration, and which vary markedly according to the
species of the fungus and the sum total of the external conditions supplied.
We shall see immediately how these considerations apply in practice.
The understanding at which we have arrived is of the first importance, as
upon a due recognition and application of it we depend for our success in
all the technical applications of biological processes. The facts of natural
selection have abundantly shown that in the struggle for existence, living organ-
isms exhibit mutual antagonism. The conditions which favour the mould fungi,
if slightly accentuated, are unfavourable to the fission fungi ; we know how the
acid excreta of cattle present a favourable nidus for moulds to a comparative
exclusion of ordinary putrefactive schizomycetes ; and among the latter, in a
mixed infection, the sum total of the conditions determines the growth of
certain kinds and the inhibition or death of others. It is a well-established
fact of the laboratory that pathogenic organisms, which have adapted them
-selves to certain special conditions of medium, are overgrown and killed out by
saprophytes in ordinary media to which the latter have free access. And again
there is no question that the conditions favourable to anaërobes are inimical to
aërobes, and vice versâ ; it would be idle to expect the best results from the
synthetically working nitrifying organisms, and from the analytic anaërobes which
split up proteids, if both be placed under the same conditions. The organisms
which effect "top" and "bottom" fermentation in the same vat are of totally
different species and cannot interchange their rôles (Mitscherlich). But even
here we must distinguish grades of antagonism ; at opposite ends of the scale it is
direct and uncompromising ; between these points it melts away into "metabiosis,"
that is to say, different species which are adapted for different purposes, follow
one another in ordered sequence, the former preparing the viable conditions for
those that come after, until those at each end of the scale are antagonistic or
work under mutually exclusive conditions. The more or less specific distribu
-tion of all living organisms in time and place is a well known fact, familiar in its
grosser aspects, but based on vital laws which may be recognized everywhere.
130
Medical Officers of the Army of India.
131
By the recognition of these laws the modern technical applications of
bacteriology have secured their greatest triumphs, as in brewing, wine ferment
-
ation, tanning, the making of butter and cheese, &c., and they have a most important
application to scientific methods of sewage "purification." Summing up at this
stage, we see, then, that bacteria are able to construct their body-substance out
of various kinds of nutrient materials, analytically or synthetically, and at the
same time to act with marked effect upon the substratum. But vital differences
in these respects are to be noted ; some species are better adapted to one method
and one set of conditions, which arc foreign to others. In the decomposition of
dead organic matter certain species are better fitted to break down the complex
compounds present at the start, while others work up the end products to final
oxidation, the complete drama being presented in a series of integral acts, in
which each species plays a defined rôle.
A brief allusion may now be made to the special nature of the vital and
chemical actions of bacteria, in virtue of which the whole of the enormous and
never-ceasing accumulation of waste organic products is transformed and enabled
to re-enter the cycle of life.
For our present purpose, these waste products may be distinguished as
nitrogenous (urea, waste proteids and their derivatives), and non-nitrogenous
(chiefly carbohydrates). As regards the former we know that the nitrogen con
-
tained in the urea and in the solid excrement is not in a form available for
plant food. It is not until this nitrogen has been removed from the organic molecule
by the process of putrefaction, and has been united to a mineral base by the
subsequent process of nitrification, that it can be disposed of by the plant. Putre
-
faction is a purely biochemical process, which only takes place under the
fundamental conditions of all vital action—temperature, moisture, etc., for it is the
work of bacteria and of bacteria only, which possess the power of breaking
up the complex proteid molecule into simpler groups. But we must recognize
that in practice ( i.e., in dealing with sewage) we never have a purely proteid
matter to work upon ; there are also non-nitrogenous matters (cellulose, etc.),
which are resolved by a series of definite fermentations ; these actions go on
side by side, and although nitrogenous bodies are putrescible and non-nitrogen
-
ous bodies are non-putrescible, we cannot distinguish a fundamental difference in
the vital forces at work in true putrefaction and in fermentation respectively, and
as a supply of nitrogen is absolutely necessary to the agents of the fermentation,
the processes are, in practice, indivisible. Both depend on biochemical forces
inherent in the living cells, and further to some extent on their secretions
which are called "enzymes," which bring about changes in the substratum
The biochemical
forces in the
transformation
of waste pro
-
ducts.
Putrefaction.
Fermentation and
enzymes.
Scientific Memoirs by
which serve to render this soluble and so available for the supply of food and
energy to the cells. Thus sugars are "inverted" and albumen peptonized
by the enzymes, and these soluble products are thus laid open to attack by
the cells. Nitrogenous bodies then are split up by putrefaction into a large
number of simpler compounds, some of which are non-nitrogenous ; first
we get albumoses and peptones, due to the action of enzymes just as in the
case of digestion (pepsin), and these later undergo a further splitting up into
certain aromatic compounds and amido-bodies ; further, fatty and aromatic
acids (non-nitrogenous) are produced, and finally we get the inorganic end pro
-
ducts, such as free nitrogen and hydrogen, ammonia, carbonic acid, methane
and sulphuretted hydrogen. All the former complex bodies are broken down
to these last, the original substratum being radically transformed
—
(1) by assimilation of food material by the living fungi ;
( 2 ) b y t h e s e c r e t o r y p r o d u c t s e l a b o r a t e d b y t h e s e ( e n z y m e s ) ;
( 3 ) b y t h e s p e c i a l p r o t o p l a s m i c a c t i v i t y o f t h e l i v i n g c e l l s .
As a result, we recognise that so far there has been no formation of oxidized
products, that there has been no oxidation,—though there has been a constant
wandering of the "fixed" oxygen atom—and we find a parallel to the processes
of digestion, in which both nitrogenous and non-nitrogenous foods are altered and
rendered soluble before the products can enter the blood stream and be oxidized.
So far, then, we have been dealing with the action of bacteria deprived of free
oxygen (an anaërobiosis), to the significance of which we have already drawn
attention.
Side by side with this resolution of the nitrogenous waste, we find also that
the waste carbohydrates, both of the original refuse and those formed in the
breaking down of nitrogenous matters, e . g ., the organic acids and fats, are similar
-
ly broken down into simpler compounds by a series of specific fermentations,
due also to the vital activity of living bacterial cells and to the enzymes they
secrete. Carbon dioxide, free hydrogen, methane, and other gases of reduction
are the characteristic end-products of carbohydrate dissolution, and as in the
former case we arrived at the final terms of the nitrogen series, we here obtain
the final term of the carbon series by processes of reduction, hydrogen being
set free in both cases.
We have now arrived at the point where we have a series of end-products
of putrefaction and fermentation, notably ammonia, free nitrogen, marsh gas,
carbonic oxide and free hydrogen, together with certain organic acids, and some
intermediate products which vary in kind and quantity according to the activity
and length of this first stage, the whole series of changes being gradual and of a
132