While certain principles of research are common to all the sciences,
each great division requires for its investigation specialized
arrangements to insure its progress. Nothing contributes so much to the
advancement of knowledge as improvements in the means of observation,
either by the discovery of new adjuncts to research, or by a fresh
adaptation of old methods. In the industrial arts, the introduction
of a new kind of raw material, the recognition that a mixture or
blending is often more serviceable than when the substances employed
are uncombined, the discovery of new processes of treating the articles
used in manufactures, the invention of improved machinery, all lead
to the expansion of trade to the occupation of the people, and to
the development of great industrial centers. In science, also, the
invention and employment of new and more precise instruments and
appliances enable us to appreciate more clearly the signification of
facts and phenomena which were previously obscure, and to penetrate
more deeply into the mysteries of nature. They mark fresh departures in
the history of science, and provide a firm base of support from which a
continuous advance may be made and fresh conceptions of nature can be
evolved.
It is not my intention, even had I possessed the requisite knowledge,
to undertake so arduous a task as to review the progress which has
recently been made in the great body of sciences which lie within
the domain of the British Association. As my occupation in life
has required me to give attention to the science which deals with
the structure and organization of the bodies of man and animals--a
science which either includes within its scope or has intimate and
widespread relations to comparative anatomy, embryology, morphology,
zoölogy, physiology and anthropology--I shall limit myself to the
attempt to bring before you some of the more important observations
and conclusions which have a bearing on the present position of the
subject. As this is the closing year of the century it will not, I
think, be out of place to refer to the changes which a hundred years
have brought about in our fundamental conceptions of the structure of
animals. In science, as in business, it is well from time to time to
take stock of what we have been doing, so that we may realize where we
stand and ascertain the balance to our credit in the scientific ledger.
So far back as the time of the ancient Greeks it was known that the
human body and those of the more highly organized animals were not
homogeneous, but were built up of parts, the _partes dissimilares_ (τὰ
ἀνόμοια μέρη {ta anomoia merê}) of Aristotle, which differed from each
other in form, color, texture, consistency and properties. These parts
were familiarly known as the bones, muscles, sinews, blood-vessels,
glands, brain, nerves and so on. As the centuries rolled on, and
as observers and observations multiplied, a more and more precise
knowledge of these parts throughout the animal kingdom was obtained,
and various attempts were made to classify animals in accordance with
their forms and structure. During the concluding years of the last
century and the earlier part of the present, the Hunters, William and
John, in our country, the Meckels in Germany, Cuvier and St. Hilaire in
France, gave an enormous impetus to anatomical studies, and contributed
largely to our knowledge of the construction of the bodies of animals.
But whilst by these and other observers the most salient and, if I may
use the expression, the grosser characters of animal organization had
been recognized, little was known of the more intimate structure or
texture of the parts. So far as could be determined by the unassisted
vision, and so much as could be recognized by the use of a simple
lens, had indeed been ascertained, and it was known that muscles,
nerves and tendons were composed of threads or fibers, and the blood
and lymph-vessels were tubes, that the parts which we call fasciæ and
aponeuroses were thin membranes and so on.
Early in the present century, Xavier Bichat, one of the most brilliant
men of science during the Napoleonic era in France, published his
‘Anatomie Générale,’ in which he formulated important general
principles. Every animal is an assemblage of different organs, each of
which discharges a function, and acting together, each in its own way,
assists in the preservation of the whole. The organs are, as it were,
special machines situated in the general building which constitutes
the factory or body of the individual. But, further, each organ or
special machine is itself formed of tissues which possess different
properties. Some, as the blood-vessels, nerves, fibrous tissues, etc.,
are generally distributed throughout the animal body, whilst others,
as bones, muscles, and cartilage, etc., are found only in certain
definite localities. While Bichat had acquired a definite philosophical
conception of the general principles of construction and of the
distribution of the tissues, neither he nor his pupil Béclard was in a
position to determine the essential nature of the structural elements.
The means and appliances at their disposal and at that of other
observers in their generation were not sufficiently potent to complete
the analysis.
Attempts were made in the third decennium of this century to improve
the methods of examining minute objects by the manufacture of compound
lenses, and, by doing away with chromatic and spherical aberration, to
obtain, in addition to magnification of the object, a relatively large
flat field of vision with clearness and sharpness of definition. When
in January, 1830, Joseph Jackson Lister read to the Royal Society his
memoir “On Some Properties in Achromatic Object-Glasses Applicable to
the Improvement of Microscopes,” he announced the principles on which
combinations of lenses could be arranged, which would possess these
qualities. By the skill of our opticians, microscopes have now for more
than half a century been constructed which, in the hands of competent
observers, have influenced and extended biological science with results
comparable to those obtained by the astronomer through improvements in
the telescope.
In the study of the minute structure of plants and animals, the
observer has frequently to deal with tissues and organs, most of
which possess such softness and delicacy of substance and outline
that, even when microscopes of the best construction are employed,
the determination of the intimate nature of the tissue, and the
precise relation which one element of an organ bears to the other
constituent elements, is, in many instances, a matter of difficulty.
Hence additional methods have had to be devised in order to facilitate
study and to give precision and accuracy to our observations. It is
difficult for one of the younger generation of biologists, with all
the appliances of a well-equipped laboratory at his command, with
experienced teachers to direct him in his work, and with excellent
text-books, in which the modern methods are described, to realize the
conditions under which his predecessors worked half a century ago.
Laboratories for minute biological research had not been constructed,
the practical teaching of histology and embryology had not been
organized, experience in methods of work had not accumulated; each
man was left to his individual efforts, and had to puzzle his way
through the complications of structure to the best of his power.
Staining and hardening reagents were unknown. The double-bladed knife
invented by Valentin, held in the hand, was the only improvement on
the scalpel or razor for cutting thin, more or less translucent slices
suitable for microscopic examination; mechanical section-cutters and
freezing arrangements had not been devised. The tools at the disposal
of the microscopist were little more than knife, forceps, scissors,
needles; with acetic acid, glycerine and Canada balsam as reagents.
But in the employment of the newer methods of research care has to be
taken, more especially when hardening and staining reagents are used,
to discriminate between appearances which are to be interpreted as
indicating natural characters, and those which are only artificial
productions.
Notwithstanding the difficulties attendant on the study of the
more delicate tissues, the compound achromatic microscope provided
anatomists with an instrument of great penetrative power. Between the
years 1830 and 1850 a number of acute observers applied themselves with
much energy and enthusiasm to the examination of the minute structure
of the tissues and organs in plants and animals.