[Footnote 1: Delivered by the Rev. Dr. Dallinger, F.R.S., at the
annual meeting of the Royal Microscopical Society, Feb. 8,
1888.--_Nature._]
Retrospect may involve regret, but can scarcely involve anxiety. To
one who fully appreciates the actual, and above all the potential,
importance of this society in its bearing upon the general progress of
scientific research in every field of physical inquiry, the
responsibilities of president will not be lightly, while they may
certainly be proudly, undertaken.
I think it may be now fairly taken for granted that, as this society
has, from the outset, promoted and pointed to the higher scientific
perfection of the microscope, so now, more than ever, it is its
special function to place this in the forefront as its _raison
d'etre_. The microscope has been long enough in the hands of amateur
and expert alike to establish itself as an instrument having an
application to every actual and conceivable department of human
research; and while in the earliest days of this society it was
possible for a zealous Fellow to have seen, and been more or less
familiar with, all the applications to which it then had been put, it
is different to-day. Specialists in the most diverse areas of research
are assiduously applying the instrument to their various subjects, and
with results that, if we would estimate aright, we must survey with
instructed vision the whole ground which advancing science covers.
From this it is manifest that this society cannot hope to infold, or
at least to organically bind to itself, men whose objects of research
are so diverse.
But these are all none the less linked by one inseverable bond; it is
the microscope; and while, amid the inconceivable diversity of its
applications, it remains manifest that this society has for its
primary object the constant progress of the instrument--whether in its
mechanical construction or its optical appliances; whether the
improvements shall bear upon the use of high powers or low powers;
whether it shall be improvement that shall apply to its commercial
employment, its easier professional application, or its most exalted
scientific use; so long as this shall be the undoubted aim of the
Royal Microscopical Society, its existence may well be the pride of
Englishmen, and will commend itself more and more to men of all
countries.
This, and this only, can lift such a society out of what I believe has
ceased to be its danger, that of forgetting that in proportion as the
optical principles of the microscope are understood, and the theory of
microscopical vision is made plain, the value of the instrument over
every region to which it can be applied, and in all the varied hands
that use it, is increased without definable limit. It is therefore by
such means that the true interests of science are promoted.
It is one of the most admirable features of this society that it has
become cosmopolitan in its character in relation to the instrument,
and all the ever-improving methods of research employed with it. From
meeting to meeting it is not one country, or one continent even, that
is represented on our tables. Nay, more, not only are we made familiar
with improvements brought from every civilized part of the world,
referring alike to the microscope itself and every instrument devised
by specialists for its employment in every department of research; but
also, by the admirable persistence of Mr. Crisp and Mr. Jno. Mayall,
Jr., we are familiarized with every discovery of the old forms of the
instrument wherever found or originally employed.
The value of all this cannot be overestimated, for it will, even where
prejudices as to our judgment may exist, gradually make it more and
more clear that this society exists to promote and acknowledge
improvements in every constituent of the microscope, come from
whatever source they may; and, in connection with this, to promote by
demonstrations, exhibitions, and monographs the finest applications of
the finest instruments for their respective purposes.
To give all this its highest value, of course, the theoretical side of
our instrument must occupy the attention of the most accomplished
experts. We may not despair that our somewhat too practical past in
this respect may right itself in our own country; but meantime the
splendid work of German students and experts is placed by the wise
editors of our journal within the reach of all.
I know of no higher hope for this important society than that it may
continue in ever increasing strength to promote, criticise, and
welcome from every quarter of the world whatever will improve the
microscope in itself and in any of its applications, from the most
simple to the most complex and important in which its employment is
possible.
There are two points of some practical interest to which I desire for
a few moments to call your attention. The former has reference to the
group of organisms to which I have for so many years directed your
attention, viz., the "monads," which throughout I have called
"putrefactive organisms."
There can be no longer any doubt that the destructive process of
putrefaction is essentially a process of fermentation.
The fermentative saprophyte is as absolutely essential to the setting
up of destructive rotting or putrescence in a putrescible fluid as the
torula is to the setting up of alcoholic fermentation in a saccharine
fluid. Make the presence of torulæ impossible, and you exclude with
certainty fermentative action.
In precisely the same way, provide a proteinaceous solution, capable
of the highest putrescence, but absolutely sterilized, and placed in
an optically pure or absolutely calcined air; and while these
conditions are maintained, no matter what length of time may be
suffered to elapse, the putrescible fluid will remain absolutely
without trace of decay.
But suffer the slightest infection of the protected and pure air to
take place, or, from some putrescent source, inoculate your sterilized
fluid with the minutest atom, and shortly turbidity, offensive scent,
and destructive putrescence ensue.
As in the alcoholic, lactic, or butyric ferments, the process set up
is shown to be dependent upon and concurrent with the vegetative
processes of the demonstrated organisms characterizing these ferments;
so it can be shown with equal clearness and certainty that the entire
process of what is known as putrescence is equally and as absolutely
dependent on the vital processes of a given and discoverable series of
organisms.
Now it is quite customary to treat the fermentative agency in
putrefaction as if it were wholly bacterial, and, indeed, the
putrefactive group of bacteria are now known as saprophytes, or
saprophytic bacteria, as distinct from morphologically similar, but
physiologically dissimilar, forms known as parasitic or pathogenic
bacteria.
It is indeed usually and justly admitted that _B. termo_ is the
exciting cause of fermentative putrefaction. Cohn has in fact
contended that it is the distinctive ferment of all putrefactions, and
that it is to decomposing proteinaceous solutions what _Torula
cerevisiæ_ is to the fermenting fluids containing sugar.
In a sense, this is no doubt strictly true: it is impossible to find a
decomposing proteinaceous solution, at any stage, without finding this
form in vast abundance.
But it is well to remember that in nature putrefactive ferments must
go on to an extent rarely imitated or followed in the laboratory. As a
rule, the pabulum in which the saprophytic organisms are provided and
"cultured" is infusions, or extracts of meat carefully filtered, and,
if vegetable matter is used, extracts of fruit, treated with equal
care, and if needful neutralized, are used in a similar way. To these
may be added all the forms of gelatine, employed in films, masses and
so forth.
But in following the process of destructive fermentation as it takes
place in large masses of tissue, animal or vegetable, but far
preferably the former, as they lie in water at a constant temperature
of from 60° to 65° F., it will be seen that the fermentative process
is the work, not of one organism, nor, judging by the standard of our
present knowledge, of one specified class of vegetative forms, but by
organisms which, though related to each other, are in many respects
greatly dissimilar, not only morphologically, but also embryologically,
and even physiologically.
Moreover, although this is a matter that will want most thorough and
efficient inquiry and research to understand properly its conditions,
yet it is sufficiently manifest that these organisms succeed each
other in a curious and even remarkable manner. Each does a part in the
work of fermentative destruction; each aids in splitting up into lower
and lower compounds the elements of which the masses of degrading
tissue are composed; while, apparently, each set in turn does by vital
action, coupled with excretion, (1) take up the substances necessary
for its own growth and multiplication; (2) carry on the fermentative
process; and (3) so change the immediate pabulum as to give rise to
conditions suitable for its immediate successor. Now the point of
special interest is that there is an apparent adaptation in the form,
functions, mode of multiplication, and order of succession in these
fermentative organisms, deserving study and fraught with instruction.
Let it be remembered that the aim of nature in this fermentative
action is not the partial splitting of certain organic compounds, and
their reconstruction in simpler conditions, but the ultimate setting
free, by saprophytic action, of the elements locked up in great masses
of organic tissue--the sending back into nature of the only material
of which future organic structures are to be composed.
I have said that there can be no question whatever that _Bacterium
termo_ is the pioneer of saprophytes. Exclude _B. termo_ (and
therefore with it all its congeners), and you can obtain no
putrefaction. But wherever, in ordinary circumstances, a decomposable
organic mass, say the body of a fish, or a considerable mass of the
flesh of a terrestrial animal, is exposed in water at a temperature of
60° to 65° F., _B. termo_ rapidly appears, and increases with a simply
astounding rapidity. It clothes the tissues like a skin, and diffuses
itself throughout the fluid.
The exact chemical changes it thus effects are not at present clearly
known; but the fermentative action is manifestly concurrent with its
multiplication. It finds its pabulum in the mass it ferments by its
vegetative processes. But it also produces a visible change in the
enveloping fluid, and noxious gases continuously are thrown off.
In the course of a week or more, dependent on the period of the year,
there is, not inevitably, but as a rule, a rapid accession of spiral
forms, such as _Spirillum volutans_, _S. undula_, and similar forms,
often accompanied by _Bacterium lineola_; and the whole interspersed
still with inconceivable multitudes of _B. termo_.
These invest the rotting tissues liked an elastic garment, but are
always in a state of movement. These, again, manifestly further the
destructive ferment, and bring about a softness and flaccidity in the
decomposing tissues, while they without doubt, at the same time, have,
by their vital activity and possible secretions, affected the
condition of the changing organic mass. There can be, so far as my
observations go, no certainty as to when, after this, another form of
organism will present itself; nor, when it does, which of a limited
series it will be. But, in a majority of observed cases, a loosening
of the living investment of bacterial forms takes place, and
simultaneously with this, the access of one or two forms of my
putrefactive monads. They were among the first we worked at; and have
been, by means of recent lenses, among the last revised. Mr. S. Kent
named them _Cercomonas typica_ and _Monas dallingeri_ respectively.
They are both simple oval forms, but the former has a flagellum at
both ends of the longer axis of the body, while the latter has a
single flagellum in front.
The principal difference is in their mode of multiplication by
fission. The former is in every way like a bacterium in its mode of
self-division. It divides, acquiring for each half a flagellum in
division, and then, in its highest vigor, in about four minutes, each
half divides again.
The second form does not divide into two, but into many, and thus
although the whole process is slower, develops with greater rapidity.
But both ultimately multiply--that is, commence new generations--by
the equivalent of a sexual process.
These would average about four times the size of _Bacterium termo_;
and when once they gain a place on and about the putrefying tissues,
their relatively powerful and incessant action, their enormous
multitude, and the manner in which they glide over, under, and beside
each other, as they invest the fermenting mass, is worthy of close
study. It has been the life history of these organisms, and not their
relations as ferment, that has specially occupied my fullest
attention; but it would be in a high degree interesting if we could
discover, or determine, what besides the vegetative or organic
processes of nutrition are being effected by one, or both, of these
organisms on the fast yielding mass. Still more would it be of
interest to discover what, if any, changes were wrought in the
pabulum, or fluid generally. For after some extended observations I
have found that it is only after one or other or both, of these
organisms have performed their part in the destructive ferment, that
subsequent and extremely interesting changes arise.
It is true that in some three or four instances of this saprophytic
destruction of organic tissues, I have observed that, after the strong
bacterial investment, there has arisen, not the two forms just named,
nor either of them, but one or other of the striking forms now called
_Tetramitus rostratus_ and _Polytoma uvella_; but this has been in
relatively few instances. The rule is that _Cercomonas typica_ or its
congener precedes other forms, that not only succeed them in promoting
and carrying to a still further point the putrescence of the
fermenting substance, but appear to be aided in the accomplishment of
this by mechanical means.
By this time the mass of tissue has ceased to cohere. The mass has
largely disintegrated, and there appears among the countless bacterial
and monad forms some one, and sometimes even three forms, that while
they at first swim and gyrate, and glide about the decomposing matter,
which is now much less closely invested by _Cercomonas typica_, or
those organisms that may have acted in its place, they also resort to
an entirely new mode of movement.
One of these forms is _Heteromita rostrata_, which, it will be
remembered, in addition to a front flagellum, has also a long fiber or
flagellum-like appendage that gracefully trails as it swims. At
certain periods of its life they anchor themselves in countless
billions all over the fermenting tissues, and as I have described in
the life history of this form, they coil their anchored fiber, as does
a vorticellan, bringing the body to the level of the point of
anchorage, then shoot out the body with lightning-like rapidity, and
bring it down like a hammer on some point of the decomposition. It
rests here for a second or two, and repeats the process; and this is
taking place by what seems almost like rhythmic movement all over the
rotting tissue. The results are scarcely visible in the mass. But if a
group of these organisms be watched, attached to a small particle of
the fermenting tissue, it will be seen to gradually diminish, and at
length to disappear.
Now, there are at least two other similar forms, one of which,
_Heteromita uncinata_, is similar in action, and the other of which,
_Dallingeria drysdali_, is much more powerful, being possessed of a
double anchor, and springing down upon the decadent mass with
relatively far greater power.
Now, it is under the action of these last forms that in a period
varying from one month to two or three the entire substance of the
organic tissues disappears, and the decomposition has been designated
by me "exhausted"; nothing being left in the vessel but slightly
noxious and pale gray water, charged with carbonic acid, and a fine,
buff colored, impalpable sediment at the bottom.
My purpose is not, by this brief notice, to give an exhaustive, or
even a sufficient account, of the progress of fermentative action, by
means of saprophytic organisms, on great masses of tissue; my
observations have been incidental, but they lead me to the conclusion
that the fermentative process is not only not carried through by what
are called saprophytic bacteria, but that a _series_ of fermentative
organisms arise, which succeed each other, the earlier ones preparing
the pabulum or altering the surrounding medium, so as to render it
highly favorable to a succeeding form. On the other hand, the
succeeding form has a special adaptation for carrying on the
fermentative destruction more efficiently from the period at which it
arises, and thus ultimately of setting free the chemical elements
locked up in dead organic compounds.
That these later organisms are saprophytic, although not bacterial,
there can be no doubt. A set of experiments, recorded by me in the
proceedings of this society some years since, would go far to
establish this (_Monthly Microscopical Journal_, 1876, p. 288). But it
may be readily shown, by extremely simple experiments, that these
forms will set up fermentative decomposition rapidly if introduced in
either a desiccated or living condition, or in the spore state, into
suitable but sterilized pabulum.
Thus while we have specific ferments which bring about definite and
specific results, and while even infusions of proteid substances may
be exhaustively fermented by saprophytic bacteria, the most important
of all ferments, that by which nature's dead organic masses are
removed, is one which there is evidence to show is brought about by
the successive vital activities of a series of adapted organisms,
which are forever at work in every region of the earth.
There is one other matter of some interest and moment on which I would
say a few words. To thoroughly instructed biologists, such words will
be quite needless; but, in a society of this kind, the possibilities
that lie in the use of the instrument are associated with the
contingency of large error, especially in the biology of the minuter
forms of life, unless a well grounded biological knowledge form the
basis of all specific inference, to say nothing of deduction.
I am the more encouraged to speak of the difficulty to which I refer,
because I have reason to know that it presents itself again and again
in the provincial societies of the country, and is often adhered to
with a tenacity worthy of a better cause. I refer to the danger that
always exists, that young or occasional observers are exposed to, amid
the complexities of minute animal and vegetable life, of concluding
that they have come upon absolute evidences of the transformation of
one minute form into another; that in fact they have demonstrated
cases of heterogenesis.
This difficulty is not diminished by the fact that on the shelves of
most microscopical societies there is to be found some sort of
literature written in support of this strange doctrine.
You will pardon me for allusion again to the field of inquiry in which
I have spent so many happy hours. It is, as you know, a region of life
in which we touch, as it were, the very margin of living things. If
nature were capricious anywhere, we might expect to find her so here.
If her methods were in a slovenly or only half determined condition,
we might expect to find it here. But it is not so. Know accurately
what you are doing, use the precautions absolutely essential, and
through years of the closest observation it will be seen that the
vegetative and vital processes generally, of the very simplest and
lowliest life forms, are as much directed and controlled by immutable
laws as the most complex and elevated.
The life cycles, accurately known, of monads repeat themselves as
accurately as those of rotifers or planarians.
And of course, on the very surface of the matter, the question
presents itself to the biologist why it should not be so. The
irrefragable philosophy of modern biology is that the most complex
forms of living creatures have derived their splendid complexity and
adaptations from the slow and majestically progressive variation and
survival from the simpler and the simplest forms. If, then, the
simplest forms of the present and the past were not governed by
accurate and unchanging laws of life, how did the rigid certainties
that manifestly and admittedly govern the more complex and the most
complex come into play?
If our modern philosophy of biology be, as we know it is, true, then
it must be very strong evidence indeed that would lead us to conclude
that the laws seen to be universal break down and cease accurately to
operate where the objects become microscopic, and our knowledge of
them is by no means full, exhaustive, and clear.
Moreover, looked at in the abstract, it is a little difficult to
conceive why there should be more uncertainty about the life processes
of a group of lowly living things than there should be about the
behavior, in reaction, of a given group of molecules.
The triumph of modern knowledge is the certainty, which nothing can
shake, that nature's laws are immutable. The stability of her
processes, the precision of her action, and the universality of her
laws, is the basis of all science, to which biology forms no
exception. Once establish, by clear and unmistakable demonstration,
the life history of an organism, and truly some change must have come
over nature as a whole, if that life history be not the same to-morrow
as to-day; and the same to one observer, in the same conditions, as to
another.
No amount of paradox would induce us to believe that the combining
proportions of hydrogen and oxygen had altered, in a specified
experimenter's hands, in synthetically producing water.
We believe that the melting point of platinum and the freezing point
of mercury are the same as they were a hundred years ago, and as they
will be a hundred years hence.
Now, carefully remember that so far as we can see at all, it must be
so with life. Life inheres in protoplasm; but just as you cannot get
_abstract matter_--that is, matter with no properties or modes of
motion--so you cannot get _abstract_ protoplasm. Every piece of living
protoplasm we see has a history; it is the inheritor of countless
millions of years. Its properties have been determined by its history.
It is the protoplasm of some definite form of life which has inherited
its specific history. It can be no more false to that inheritance than
an atom of oxygen can be false to its properties.
All this, of course, within the lines of the great secular processes
of the Darwinian laws; which, by the way, could not operate at all if
caprice formed any part of the activities of nature.
But let me give a practical instance of how what appears like fact may
override philosophy, if an incident, or even a group of incidents,
_per se_ are to control our judgment.
Eighteen years ago I was paying much attention to vorticellæ. I was
observing with some pertinacity _Vorticella convallaria_; for one of
the calices in a group under observation was in a strange and
semi-encysted state, while the remainder were in full normal activity.
I watched with great interest and care, and have in my folio still the
drawings made at the time. The stalk carrying this individual calyx
fell upon the branch of vegetable matter to which the vorticellan was
attached, and the calyx became perfectly globular; and at length there
emerged from it a small form with which, in this condition, I was
quite unfamiliar; it was small, tortoise-like in form, and crept over
the branch on setæ or hair-like pedicels; but, carefully followed, I
found it soon swam, and at length got the long neck-like appendage of
_Amphileptus anser_!
Here then was the cup or calyx of a definite vorticellan form changing
into (?) an absolutely different infusorian, viz., _Amphileptus
anser_!
Now I simply reported the _fact_ to the Liverpool Microscopical
Society, with no attempt at inference; but two years after I was able
to explain the mystery, for, finding in the same pond both _V.
convallaria_ and _A. anser_, I carefully watched their movements, and
saw the _Amphileptus_ seize and struggle with a calyx of
_convallaria_, and absolutely become encysted upon it, with the
results that I had reported two years before.
And there can be no doubt but this is the key to the cases that come
to us again and again of minute forms suddenly changing into forms
wholly unlike. It is happily among the virtues of the man of science
to "rejoice in the truth," even though it be found at his expense; and
true workers, earnest seekers for nature's methods, in the obscurest
fields of her action, will not murmur that this source of danger to
younger microscopists has been pointed out, or recalled to them.
And now I bid you, as your president, farewell. It has been all
pleasure to me to serve you. It has enlarged my friendships and my
interests, and although my work has linked me with the society for
many years, I have derived much profit from this more organic union
with it; and it is a source of encouragement to me, and will, I am
sure, be to you, that, after having done with simple pleasure what I
could, I am to be succeeded in this place of honor by so distinguished
a student of the phenomena of minute life as Dr. Hudson. I can but
wish him as happy a tenure of office as mine has been.
* * * * *