A. de (Anton) Bary.

Lectures on bacteria online

. (page 1 of 18)
Online LibraryA. de (Anton) BaryLectures on bacteria → online text (page 1 of 18)
Font size
QR-code for this ebook

















Fellow of Magdalen College, Oxford



Fellow of Magdalen College and She rardian Professor of Botany
in the University of Oxford




[ All rights reserved ]





THIS translation of Professor De Bary's ' Vorlesungen iiber
Bacterien' has been prepared because there is at present
no book in English which gives in like manner ' a general
view of the subject ' of Bacteria, and ' sets forth the known
facts in the life of Bacteria in their connection with those
with which we are acquainted in other branches of natural

I. B. B.

OXFORD, 1887.


THE present work is in the main a short abridgement of a
number of lectures, some of which were delivered in a connected
series as a University course, others as occasional and separate
addresses. The form of the lectures has been occasionally
altered to meet the difference between a written treatise and free
oral delivery accompanied by demonstrations. Some things
have been omitted and others added, especially some matters of
general importance which were not published or did not become
known to me till after the delivery of the actual course.

The lectures were an attempt to introduce an audience com-
posed of persons of very different professional pursuits, medical
and non-medical, to an acquaintance with the present state of
knowledge and opinion concerning the much discussed questions
connected with Bacteria. They had, therefore, to give such a
survey of the subject as would be intelligible to all who were
not strangers to the elements of a scientific training, and
especially to set forth the known facts in the life of the
Bacteria in their connection with those with which we are
acquainted in other branches of natural history.

A survey of the present extensive literature of the subject,
and of the almost daily additions to it, shows the existence of
many serviceable and some excellent publications, but at the
same time also of much that is mistaken and obscure. The
scientific and semi-scientific converse of the day, if I may use

viii Preface.

the expression, is greatly influenced by works of the latter kind,
and the chief reason for this, if I am not mistaken, lies in the
absence of a general view of the subject itself and of its relations
to other portions of natural history; we cannot see the wood for
the trees. An attempt to give such a view would be no mere
superfluous addition to existing works, and this consideration
was a decisive reason in the judgment of myself and of those
who gave me their encouragement for afterwards transcribing
and publishing my lectures.

The present treatise, therefore, must not be expected to be
a Bacteriology, or even to report and enumerate all the details
which may be of interest and importance ; it should rather
serve only as a guide for the direction of the student through
these details.

Many readers, devoted to the study of the Bacteria, will be
familiar with the literature or with the guides to it before they
take up this book. For the sake of those who seek to gain
some knowledge of the subject from its perusal, and also for
the purpose of naming the most important sources of informa-
tion which I have made use of along with my own investigations.
I have added a few notices of publications at the end of the
volume, and have indicated by numerals in brackets the places
in the text to which the citation marked with the same number

So much by way of introduction to this little work. I trust
that it may do something to clear up existing views on the
subject of the Bacteria, and to lead the investigation of these
organisms from its present stage of storm and pressure into the
ways of quiet fruitful labour and increase of knowledge.

The above with the omission of one sentence is the word-
ing of the preface written in July, 1885, for the first edition of
this book. The kindly reception which it met with can only

Preface. ix

have been due to the circumstance that the form in which the
subject was presented in it was the one best adapted to attain
the object proposed ; it could scarcely be that there was any-
thing new in it. Hence the form and limits of the second
edition which is now demanded are alike prescribed to me ;
it must be made as like as possible to the first. This has been
done ; the original frame is unaltered, and the old matter still
appears in it in many places. On the other hand, much pro-
gress has been made in the period which has elapsed since the
work was originally composed, and some new views have been
laid down which could not be disregarded. The new edition,
therefore, will be found to contain not only some editorial
improvements in the special descriptions, but also various
important alterations.

These observations apply also to the notes at the end of the
work, except that I have introduced somewhat more critical and
explanatory remarks than in the first edition.


STRASSBURG, Oct., 1886.


I. Introduction. Bacteria or Schizomycetes and Fungi. Struc-
ture of the Bacterium-cell . . . : . . . i

II. Cell-forms, cell-unions, and cell-groupings .... 9

III. Course of development. Endosporous and Arthrosporous

Bacteria . . . ...'*. . . 15

IV, Species of Bacteria. Distinct species denied. The grounds
for this denial insufficient. Method of investigation.
Relationships of the Bacteria and their position in the
system 24

V. Origin and distribution of Bacteria . . . . . 37

VI. Vegetative processes. External conditions : temperature and
material character of the environment. Practical ap-
plication of these in cultures, in disinfection, and in
antisepsis . . . . . ' Y Y . 49

VII. Relation to and effect upon the substratum. Saprophytes
and Parasites. Saprophytes as exciting decompositions
and fermentations. Characteristic qualities of Forms
exciting fermentation . . . . . . . 64

VIII. Most important examples of Saprophytes. The nomenclature
explained. Aquatic Saprophytes: Crenothrix, Cladothrix,
Beggiatoa; other aquatic forms . . -. . .- . 7 2

IX. Saprophytes which excite fermentation. Fermentations of
urea. Nitrification. Acetous fermentation. Viscous
fermentations. Formation of lactic acid. Kefir. Bacillus
Amylobacter. Decompositions of proteid. Bacterium
Termo 83

X. Parasitic Bacteria. The phenomena of parasitism . . 107

xii Contents.


XI. Harmless parasites of warm-blooded animals. Parasites of
the intestinal canal. Sarcina. Leptothrix, Micrococci,
Spirillum, Comma-bacillus of the mucous membrane of
the mouth 115

XII. Anthrax and Fowl- cholera 122

XIII Causal connection of parasitic Bacteria with infectious
diseases, especially in warm-blooded animals.
Introduction . . . ' .

Relapsing fever



Asiatic Cholera '. - .... . . ... \

Traumatic infectious diseases . .
Erysipelas . . f . ; . .

Trachoma and xerosis ; pneumonia, leprosy, syphilis,

cattle-plague . . . . . ,, .. . 169

Malaria . . . . . . . .170

Typhoid fever and diphtheria . . . ' " ' ". ' - . 171
Infectious diseases in which the presence of contagium

vivum has not been demonstrated . . . . 1 74

XIV. Diseases caused by Bacteria in the lower animals and in

Diseases of insects . . . v ..." . _ ,' . 174

Diseases of plants . -. - , . ; : : . - . . 177

Conspectus of the Literature and Notes ..'.'.. . 181
Index of Names . . . ... . . . 191


Introduction. Bacteria or Schizomycetes and Fungi.
Structure of the Bacterium-cell (1).

THE purpose of these lectures is to give some account of the
present state of our knowledge respecting the objects included
under the name of Bacteria. It is unnecessary to enlarge upon
the manifold interest attaching to these organisms at a time when
the statement urged daily on the educated public does not fall far
short of saying, that a large part of all health and disease in the
world is dependent on Bacteria. If we are therefore spared that
customary portion of the introduction to a lecture which seeks
to impress the hearer with the importance of the subject, it be-
comes the more necessary to give prominence from the first to
the reverse side of the question ; that is to say, to call special
attention to the fact, that the problem presented to us can only
be solved by quiet scientific examination from every possible
point of view of the objects under consideration; and a study of
this kind is dry rather than exciting, or to use a common ex-
pression, interesting. But this should not deter any one who
is really desirous of acquiring some knowledge of our subject.

The order of our remarks will follow the natural arrangement
.of the subject before us; and our first task therefore will be to
''enquire what Bacteria are ; in other words, to make ourselves
acquainted with their conformation, their structure, their de-
velopment, and their origin in connection with their development.
Next, we have to enquire what they do, what good and what

2 Lectures on Bacteria. [ i.

harm they occasion, that is, we must study their vital processes
and the effects which these produce on the objects outside of

We begin with the first question, and we will first of all bestow
a moment's consideration on the name.

Bacteria, meaning rod-shaped animalcules or plantlets, from
the rod-like form which many of them exhibit, are also termed
Fission-fungi or Schizomycetes. The two expressions are not,
strictly speaking, of the same import.

The reason of this is that the word Fungi is used in two
senses. In the one it is the name for those lower flowerless
plants which are devoid of chlorophyll, the green colouring
matter of leaves, and hence exhibit certain definite peculi-
arities in the process of their nutrition. We shall speak of
these peculiarities at greater length in succeeding lectures;
at present we will only make the preliminary observation,
that all organisms devoid of chlorophyll require already formed
organic carbon-compounds for their nutrition, and cannot obtain
the necessary supplies of carbon from the carbon dioxide which
finds access to them. The construction of organic compounds
from this substance is bound up with the presence of chlorophyll
and analogous bodies.

Fungi in this sense are therefore a group characterised by
definite physiological peculiarities the mark of which is the
absence of chlorophyll, somewhat in the same way as birds and
bats may be grouped together under the head of winged

In the other sense, that of descriptive taxonomic natural
history, the term Fungi denotes a group of lower plant-forms
distinguished by definite characteristics of structure and develop-
ment, and recognised at once when we see a mushroom or a
mould. The members of this group are all as a matter of fact
devoid of chlorophyll, but they might contain chlorophyll and
yet belong to this group, just as a bird may have no apparatus
for flight and yet be allowed to be a bird. To these Fungi, as

i.] Structure of the Bacterium-cell. 3

defined by natural history and not by physiological characters
only, Bacteria are as little related in structure and development
as bats are to birds ; the relationship is even less, because there
are a few, though only a few, true Bacteria which contain chlo-
rophyll and decompose carbon dioxide, and which are therefore
not Fungi in the physiological sense.

For these reasons we shall be more strictly correct if we
speak on the present occasion of Bacteria rather than of Fission-
fungi ; but so long as we are quite clear as to the difference in
the meaning of the two words, it is a matter of no importance
which we use.

The conformation, structure, and growth of Bacteria are
extremely simple, if we put out of sight certain phenomena of
propagation and consider only the vegetative state.

Bacteria appear in the form of round or cylindrical rod-shaped,
rarely fusiform, cells of very minute size. The diameter of the
round cells or the transverse section of the cylindrical cells is in
most cases about o'ooi mm. ( = i micromillimetre = i /z) or even
less. The length of the cylindrical cells is 2-4 times the trans-
verse section, rarely more. There are only a few forms with dis-
tinctly larger dimensions. Putting aside, for later consideration,
the forms from the group of Beggiatoa, Crenothrix and their
allies, which differ to some extent in this and other respects from
the rest of the Bacteria, the greatest breadth yet observed is 4 /a,
the measurement given by Van Tieghem for the rod-shaped
cells of Bacillus crassus.

We are obliged to apply the term cells to those minute bodies,
because they grow and divide like plant-cells, and also because
all that we know of their structure agrees with the corresponding
phenomena in plant-cells. It is true that their small size does
not permit of our going at present very deeply into the minutiae
of their structure. Cell-nuclei, for instance, have not yet been
observed in them ; but this is the case in many small cells of
other plants of a low order of growth, especially Fungi, and till
recent times it was the case with respect to all fungal cells.

B 2

4 Lectures on Bacteria. [$ i.

Perseverance and constantly improving methods of research
advance our knowledge as time goes on.

The Bacterium-cell is mainly composed of a portion of
protoplasm, which in the smaller and in most also of the
larger forms appears as an entirely homogeneous translucent
substance, but in some of the larger forms it is also often finely
granular or shows a different kind of structure, which will be
further described presently. It consists, as Nencki (2) has shown
in a number of cases, chiefly of peculiar albuminoid compounds
(mycoprotein, anthrax-protein) which vary with the species, and
its behaviour, when the usual empirical reagents are applied to it,
agrees in general with that of the protoplasmic bodies of other
organisms the yellow and brownish-yellow coloration with
solutions of iodine, and the absorption of, that is to say, the
intense staining by, preparations of carmine and anilin dyes.
Yarious specific differences occur in individual cases in the
behaviour of the protoplasm to these colouring reagents, and
supply very useful marks of distinction in certain cases which
will be mentioned again on subsequent occasions.

We have already alluded to the fact that the protoplasm of
certain Bacteria described by Engelmann and van Tieghem,
for example, Bacillus virens, v. T., is coloured by chlorophyll,
being of a uniform pale leaf-green hue. In the very large
majority of cases it is colourless ; most Bacteria, not only when
isolated under the microscope but also when collected into
masses, have a pure or dirty-white colour, and in the latter case
show various shades of tint inclining to gray or yellow, &c.,
which the practised observer may even apply to the determina-
tion of species. On the other hand, there are not a few Bacteria
which exhibit lively colours when they are associated in masses,
yellow, red, green, violet, blue, brown, &c., according to the
individual. Schroter has collected together a number of such
cases. How far these colours belong to the protoplasm itself
or to its envelope, the cell-membrane, which will be described
presently, or to both, cannot in most cases be certainly ascer-

i.] Structure of the Bacterium-cell. 5

tained, because the individual cell is so small that it does not by
itself show any indications of colour. In some comparatively
large forms, those, for instance, grouped together by Zopf under
the name of Beggiatoa roseo-persicina, it can be seen that the
living protoplasmic body shares at least in the coloration, which
in this case is a bright red. Some of the colouring matters in
question have been submitted to closer examination and have
even received special names, as bacterio-purpurin, &c. In their
optical qualities they show various points of resemblance to
anilin dyes, as is indicated by the above name ; but we must
not infer from this that the chemical composition is analogous.

Among other phenomena of frequent recurrence in the
structure and contents of the protoplasm the starch-reaction
claims special attention. Bacillus Amylobacter and Spirillum
amyliferum, v. T., in certain stages of their development have
this peculiarity, that a portion of their protoplasm, distinguished
from the remainder by being somewhat more highly refringent,
when treated with watery solution of iodine assumes an indigo-
blue colour like starch-grains, or speaking more exactly like
the granulose which forms a large part of their substance. The
conditions under which this phenomenon makes its appearance
and again disappears will be discussed at greater length below.
E.Hansen'sMicrococcusPasteurianus also and usually Leptothrix
buccalis show the granulose-reaction. We may also mention in
this connection the occurrence of sulphur-granules in Beggiatoa,
referring the reader to Lecture VIII for further particulars.

The protoplasmic body of the Bacteria is surrounded by a
membrane or cell-wall. This membrane in one of the species
which have been examined, Sarcina ventriculi (see Lecture XI),
possesses, as far as is at present known, the qualities of typical
plant-cellulose-membrane; it is firm and thin, and assumes
the characteristic violet colour when treated with Schulze's
solution. But in the majority of cases there is no trace of the
characteristic coloration of cellulose. In single specimens
scattered about in a fluid the membrane appears under the

6 Lee hires on Bacteria. [ i.

microscope as a delicate line drawn round the free surface, and
forming the boundary between contiguous cells. It may even be
seen distinct from the protoplasm in the larger forms by the aid
of reagents which strongly contract the protoplasm and colour it
at the same time without affecting the membrane, for instance
alcoholic solution of iodine (see Fig. i, p\ It is plainly
shown also in the formation of spores which will be described
in Lecture III. This membrane, which lies close upon
the protoplasm, is in certain forms at least, the species of
Beggiatoa and Spirochaete for example, highly extensible and
elastic, for it is seen to follow the curves often made by the
elongated organism, and the protoplasm can alone be the active
agent in producing these. But the membrane which thus directly
covers the protoplasm is certainly in all cases only the innermost
firmer layer of a gelatinous envelope surrounding the proto-
plasmic body. This may be seen directly in not a few forms
if observed attentively under the microscope, when the cells
or small aggregations of cells lie isolated in a fluid. Large
masses of Bacteria are always more or less gelatinous or slimy
when in a sufficiently moist condition. When the cells are
dividing, the outer layers of the membrane may sometimes be
seen to swell up in succession. Hence, speaking generally, we
may say that the cells of Bacteria have gelatinous membranes,
with a thin and comparatively firm inner layer. The consistence
of the mucilage and its capability of swelling in fluids differ
in different cases, changing gradually, but this point will be
considered again presently at greater length.

The possession of gelatinous membranes of this kind is com-
mon to the Bacteria and to various other organisms of the lower
sort, of which Nostocaceae and some Sprouting and Filamentous
Fungi may be quoted as examples. In Bacteria, as in the latter
plants, the gelatinous membrane has been shown in a number
of forms which have been examined to consist of a carbohydrate
closely related to cellulose ; this is specially the case in the Bac-
terium of mother of vinegar and in Leuconostoc, the frog-spawn-

i.] Stricture of the Bacterium-cell. 7

bacterium of sugar factories. On the other hand, Nencki found
that the membranes of certain putrefactive Bacteria not distinctly
determined are in a great measure composed, like the proto-
plasm which they enclose, of the mycoprotein mentioned on
page 4. Lastly, a statement of Neisser (65) must also be men-
tioned in this place ; he suspects, from the behaviour of the
membrane or envelope of the Bacterium of xerosis conjunctiva
in the presence of reagents, that it contains a considerable amount
of fatty matter. Further investigation into these points is at all
events desirable. The membranes of Cladothrix and Crenothrix
which live in water are often coloured brown by the introduc-
tion of compounds of iron.

Many Bacteria are capable of free movement in fluids. They
rotate about their longitudinal axis, or they oscillate like a
pendulum and move rapidly forwards or backwards. Search
has consequently been made for organs of motion, and these
are supposed to have been found in certain very slender filiform
appendages, cilia or flagella, which are attached singly or in
pairs to the extremities of rod-shaped Bacteria. Such cilia are
present in many relatively large cells not belonging to the Bacteria,
and endowed like them with the power of free movement in fluids,
the swarm-cells, for example, and swarm-spores of many Algae
and some Fungi. In these cases the cilia oscillate rapidly as
long as the movement continues, causing rotation round the
longitudinal axis, and may consequently be considered to be
the active organs of motion. In the swarm-cells of the Algae
they are processes, projections as it were, from the surface of
the protoplasmic body, and belong therefore to the protoplasm.
When the protoplasm is surrounded by a membrane, the cilia
pass out through openings in the membrane. But no such
characteristic structural conditions have been observed in the
Bacteria. Delicate thread-like processes have certainly been
observed occasionally at the points above-mentioned in coloured
specimens which have been exposed to desiccation. That they
are really there and not, or at least not always, in the imagina-

8 Lectures on Bacteria. [ i.

tion of the observer only, is proved by the fact that they
appear in photographs. But in an overwhelming majority of
cases no cilia can be seen, though the Bacteria are capable of
independent movement and are examined with the best optical
aids after being killed and coloured. Where they are found,
they are as van Tieghem rightly says, not processes of the
protoplasmic body, but belong to the membrane, as is shown
by their behaviour with reagents, and must therefore be con-
sidered to be thread-like extensions of the soft gelatinous
membrane-layers. They have accordingly nothing in common
with the cilia of swarm-spores of the Algae, and cannot therefore
be regarded as organs of motion, since it was only from the
analogy of the cilia in the Algae that this function was inferred.
Such is the state of the case at least in the great majority of
species. Whether there are any exceptional cases must be deter-
mined by further investigation. It should be added, that among
lower organisms there are some comparatively large forms,
the Oscillatorieae, for example, the near relatives according to
our present knowledge of the Bacteria a point to be further
considered below which show similar movements, though no
cilia or other distinct organs of motion have been observed in
them. It follows that analogy does not require the discovery
of cilia in the Bacteria.

Vegetating Bacterium-cells multiply by successive division,
each cell forming two daughter-cells. When a cell has reached
a certain size, a fine transverse line makes its appearance in it,
dividing the cell into two equal parts. This line is subse-
quently shown by its gelatinous swelling to be the commence-
ment of a cell-membrane. This agrees with the phenomena
observed in the divisions of larger plant-cells, and there is
nothing to prevent our assuming that the details of the process
of division, which the minuteness of the object makes it impos-
sible to observe directly, are the same in both cases.

It must be acknowledged that the transverse wall which
appears as the cell divides is often so delicate as easily

ii.] Cell-forms. 9

to escape observation, and becomes visible only under the influ-

1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Online LibraryA. de (Anton) BaryLectures on bacteria → online text (page 1 of 18)