tries to understand how a contrivance acts, what advantage it confers
upon its possessor, and by what steps it was perfected. The minute
variations of species are as capricious as the form of the stones
which accumulate at the foot of a precipice; natural selection turns
fortuitous variations to account for the advantage of the species as
a builder might turn to account the shapes of the stones. Man himself
can employ variations for frivolous or even base purposes, as when he
produces toy-spaniels or bull-dogs.[50] The adjustments of organic
structures often move our wonder by their perfection. One reason why
they so far exceed the adjustments made by wind, frost, or moving water
is that the process has been so protracted; in a worm or an insect we
see the last stage of an adaptation which has been continuously at
work for untold geological periods. Another reason is that the thing
adapted is alive, sensitive, and capable of responding to the subtlest
imaginable influences.
_Darwinism and Non-biological Studies._—The theory of organic
evolution has already produced a visible effect upon non-biological
studies. Bagehot has applied Darwinian principles to the interpretation
of history and politics. Philologists recognise a process very like
that of natural selection in the modification of words. The usages
of language are inherited from generation to generation; one idiom
competes with another, that persisting which best suits the temper
or the convenience of the nation. Philology has like zoology its
chains of descent, its breeds or dialects, its species or languages,
its fossils (dead languages), its dominant and declining forms, its
vestiges (such as letters, still retained, though no longer sounded).
Psychology is already in part experimental and evolutionary, and seems
as if it would attach itself more and more closely to physiology,
detaching itself in the same measure from metaphysics. The change may
be attributed to two growing convictions: (1) That the experimental
method is more trustworthy than the speculative; and (2) that the mind
of man is not a thing apart, but an enhanced form of powers manifest in
the lower animals. Sociology finds its most practicable and its most
urgent sphere of work in the problems of selection and race, which are
naturally examined in the light of Darwinian principles. The new study
of Comparative Religion aims at the impartial examination of all forms
of religious experience, and is evolutionary in proportion as it is
scientific. One of its conclusions, by no means universally accepted
as yet, is the recognition of conscience as "the organised result of
the social experiences of many generations" (Galton). Comparative
Religion can already show in outline how by slow degrees magical rites
passed into polytheistic worship, how polytheism became simplified and
elevated, and how ethical motives at length became influential if not
predominant.
Pasteur's Experimental Study of Microbes.
The same difficulty arises with Pasteur as with Darwin; his life-work
has already been described often and well. Readers unversed in science
have only to turn to the _Vie de Pasteur_, written by his son-in-law,
Vallery-Radot, to find a luminous account, giving just so much detail
as makes the discoveries intelligible and interesting. If shorter
sketches are demanded, they exist. We must therefore above all things
be brief, and content ourselves with reminding the reader of facts
which, in spite of their recent date, are as well known as anything in
the history of science.
Chemists will claim Pasteur as one of their number, and we do not
dispute the claim. Trained in experimental methods by the chemical
laboratory, he devoted his best powers to the study of living things,
and, without ceasing to be a chemist, became one of the greatest of
biologists.
Pasteur's chief work was of course the experimental investigation of
living particles which float in the air—what we may call _live dust_.
Before his day such particles had been seen, named, and classified;
some few had been studied in their action and effects. Most of them
are plants of low grade, simplified to the last point for the sake of
minuteness, on which their ready dispersal depends.
_Yeast._—Van Helmont, early in the seventeenth century, when the
microscope had not yet become an instrument of research, attempted to
investigate the fermentation of beer, and made acquaintance with the
properties of the gas which is evolved, his _gas silvestre_, which
was afterwards called fixed air, or carbonic acid. Leeuwenhoek about
1680 examined yeast by his microscopes, and discovered that it is made
up of globules which often cohere, and that these globules give off
bubbles of gas. Then comes a long interval, during which nothing was
done to elucidate the process of fermentation. It was not till 1837
that Caignard-Latour and Schwann, independently of each other, showed
that yeast-globules multiply by budding, and are therefore to be set
down as living things, probably plants of a simple kind. Twenty years
more passed without sensible progress; during this time chemists were
striving to prove that the alcohol was produced by contact-action, and
that the globules were of no practical importance. By the year 1860
Pasteur was engaged upon the problem. It is well known that he arrived
at a firm conviction that living yeast-cells are essential to the
production of alcohol. It has since been discovered that the enzyme
(unorganised ferment of older writers) secreted by living yeast-cells
can change sugar into alcohol after the cells themselves have been
destroyed, and that other plants besides yeast-cells secrete the same
enzyme when deprived of oxygen.
_Bacteria._—Another and even more important chapter in the history of
air-wafted organisms was opened by the indefatigable Leeuwenhoek. In
1683 he wrote a letter to the Royal Society which makes mention for
the first time of bacteria, which he found upon his own teeth, and
described as minute rods; some of them moved with surprising agility.
For nearly two hundred years little more was done. A few bacteria
were named and classified, and there the matter rested until Schwann
proved experimentally that putrefaction is just as much the work of
living microscopic organisms as alcoholic fermentation. In 1857 and the
following years Pasteur not only confirmed the work of Schwann, which
had been received by the majority of chemists with distrust, but went
on to show that the lactic, butyric, and ammoniacal fermentations also
depend upon the activity of bacteria. The happy thought struck him
that they might be studied alive—a possibility which he soon realised
in practice, and upon which the new science of bacteriology largely
rests. From about the year 1873 he began to occupy himself seriously
with contagion, which he suspected to be connected with specific
aerial germs. Davaine and others had years before observed in the
blood of sheep and cattle which had died of "charbon" (anthrax) minute
"bâtonnets" (bacilli). Pasteur's published results induced Davaine to
ask whether his "bâtonnets" might not be the cause of "charbon." Again,
it was Pasteur's results which induced Lister to make experiments
in the field of antiseptic surgery. Pasteur wasted no time upon the
curiosities of bacterial life. His first studies on fermentation
suggested that specific diseases may be propagated by microscopic
germs, and that such cases of spontaneous generation as had hitherto
escaped refutation might be explained by the access of live dust. The
identification and biological history of the organisms interested him
only as a step towards sure methods of controlling, and, if necessary,
destroying, them; of mitigating their virulence by inoculation; of
rendering animals immune against them; or of stamping out the disease
by isolation. All this is happily too well known for repetition here.
The story, with its many dramatic incidents, can be read in the pages
of Vallery-Radot.
Hardly less important than the bacteria which destroy life or endanger
the products of human industry are the beneficent forms, some of
which have in all ages co-operated with man, while others can only
be employed by those who possess knowledge and skill. None are so
important to our welfare as the bacteria which renew the fertility of
the soil. But for the soil-bacteria farm-yard manure would be useless
to the crop, for it is they which render it fit for assimilation.
Now the bacteria of the soil have their natural enemies, the most
mischievous being certain Protozoa, such as Amœba and its kindred.
As soon as this fact was grasped, likely remedies were thought of;
indeed, one remedy was suggested without any guidance from theory by a
vine-grower of Alsace, who treated his soil with carbon disulphide to
destroy phylloxera, and found that in so doing he had notably enhanced
its fertility. Heating to the temperature of boiling water destroys
the soil-protozoa and at the same time the bulk of the soil-bacteria.
The bacteria, however, soon multiply more than ever by reason of the
absence of their enemies, and a soil cleared of protozoa yields for
a few years appreciably richer crops. Of other useful bacteria the
briefest notice must suffice. Wine, beer, cheese, and tobacco owe to
certain of them distinct flavours, for which the customer is willing to
pay high. Leather in certain stages of manufacture, indigo, and woad
require the access of other forms. If we also bear in mind the part
which yeast plays in the every-day manufacture of bread, wine, and
beer, and the part which the vinegar-mould plays in the manufacture
of acetic acid, we shall get some notion of the industrial importance
of the various micro-organisms. Not a little of the control which we
exercise over them we owe directly or indirectly to Pasteur.
The career of Pasteur exhibits a striking unity. His first research,
which dealt with a subject so remote from the ordinary studies of the
biologist as the crystalline forms of tartrates, made him acquainted
with activities, hitherto unsuspected, of minute forms of life. The
hope of aiding the industries of Lille, Orleans, and France kept
him long engaged upon ferments. If he turned aside to examine the
superstition of spontaneous generation, it was to protect his methods
from misconstruction. An apparent break in his programme of work was
forced upon him by the silkworm pestilence. It proved to be no real
break, for pébrine and flacherie were both bacterial diseases. At a
comparatively early date (1863) he wrote that his chief ambition was
to throw light on the spread of contagious diseases; he could not then
foresee that he was destined, not only to elucidate, but in a measure
to control them. Around his tomb are inscribed words, each of which
commemorates a signal service to his fellow-men: "1848, Molecular
dissymetry. 1857, Fermentations. 1862, Spontaneous generation. 1863,
Studies of wine. 1865, Silkworm diseases. 1871, Studies on beer. 1877,
Contagious diseases of animals. 1880, Vaccination against contagious
diseases. 1885, Prevention of hydrophobia." These manifold researches
form a continuous chain, each being linked to what precedes and
follows. The devotion by which all were inspired, beginning with
devotion to science and the fatherland, ended by embracing all mankind.
* * * * *
Biology, which in the sixteenth century sent out only a few feeble
shoots, has now become a mighty tree with innumerable fruit-laden
branches. The vigour of its latest outgrowths encourages confident
hopes of future expansion.
[44] Titius of Wittenberg, who published in 1766 what is commonly
called Bode's law of planetary distances, objected to the Linnean
system on the ground that it multiplied the principle of division. (_De
divisione animalium generali_, 1760.)
[45] _Origin of Species_, chap. xiii.
[46] _Geol. Survey Memoirs_, 1846.
[47] By a curious and no doubt accidental coincidence, Darwin employs
the same remarkable metaphor which had occurred to Iordanes in the
sixth century A.D. Iordanes calls the north the _officina gentium_.
[48] Introduction to _Entomology_, Introductory Letter.
[49] _Life and Letters_, Vol. I., chap. ii.
[50] Darwin, _Variation of Plants and Animals under Domestication_,
Concluding Remarks.
CHRONOLOGICAL TABLE
1200-1850
(The date of a discovery is the date of first publication, where this
is known.)
1202. Arabic numeration introduced into Europe by Leonardo of Pisa
(Liber Abaci); it spread slowly, and did not become universal till the
middle of the seventeenth century.
1214-1294. Roger Bacon.
1265-1321. Dante.
1271-1295. Travels of Marco Polo.
1304~1374. Petrarch.
1324?-1384. Wycliffe.
1340?-1400. Chaucer.
1410. Wood-engraving introduced about this time.
1423. Earliest known block-book.
1450? Mazarin Bible, printed by moveable types.
1453. Taking of Constantinople by the Turks.
1466?-1536. Erasmus.
1471-1528. Albert Durer.
1472-1543. Copernicus.
1475-1564. Michael Angelo.
1477-1576. Titian.
1483-1520. Raphael.
1483-1546. Martin Luther.
1492. First voyage of Columbus.
1497-1498. Voyage of Vasco da Gama to India by the Cape.
1516. More's _Utopia_.
1517. Luther's theses.
1519-1521. Mexico conquered by Cortez.
1519-1522. Circumnavigation of the globe by a ship of Magellan's
squadron.
1530-1536. Brunfels' _Herbarum vivæ eicones_. Confession of
Augsburg.
1532. Peru conquered by Pizarro.
1534. Society of Jesus founded by Loyola.
1539. Bock's _New Kreutterbuch_ (without figures); 2nd ed. (with
figures) 1546.
1542. Fuchs' _Historia Stirpium_.
1543. Copernicus' _De Revolutionibus Orbium Celestium_. Vesalius'
_Fabrica Humani Corporis_.
1545. Botanic garden at Padua founded.
1545-1564. Council of Trent.
1547. Botanic garden at Pisa founded.
1551. Belon's _Histoire Naturelle des estranges poissons marins_.
1551-1587. Gesner's _Historia Animalium_.
1553. Belon's _De aquatilibus_, etc., and his _Observations de
plusieurs singularitez_, etc. (Travels in the Levant.)
1554. Rondelet's _De piscibus marinis_.
1555. Belon's _Histoire de la nature des Oyseaux_. Rondelet's
_Universæ aquatilium Historiæ pars altera_.
1564-1616. Shakespeare.
1564-1642. Galileo.
1566. Revolt of the Netherlands.
1571. Battle of Lepanto (advance of the Turks checked).
1571-1630. Kepler.
1572. Massacre of St. Bartholomew.
1576. L'Obel's _Plantarum seu Stirpium Historia and Adversaria_.
1577-1580. Drake's circumnavigation.
1583. Cesalpini's _De Plantis_.
1588. The Invincible Armada.
1596-1650. Descartes.
1600. Olivier de Serres' _Théâtre d'Agriculture_.
1601. Clusius' _Rariorum plantarum Historia_.
1605. Clusius' _Exoticorum libri decem_.
1610. Galileo'smicroscope invented about this time.
1614. Napier's Logarithms.
1618-1648. Thirty Years' War.
1620. Voyage of _Mayflower_. Bacon's _Novum Organum_.
1621. Aselli re-discovers the lacteals.
1623. C. Bauhin's _Pinax Theatri Botanici_.
1626. Jardin des Plantes founded.
1628. Harvey's _De motu cordis et sanguinis_ published, the lectures
had been delivered in 1614.
1635. French Academy founded.
1638. First authenticated cure of fever by chincona bark (in Peru).
1642. New Zealand and Van Dieman's Land discovered by Tasman.
1642-1727. Newton.
1643. Barometer invented by Torricelli.
1650? Air-pump invented by Otto von Guericke. Thoracic duct discovered
by Pecquet.
1653. Lymphatic vessels discovered by Rudbeck.
1660. Royal Society founded; incorporated 1662. Boyle's _Spring of
Air and its Effects_. Ray's _Catalogus Plantarum circa Cantabrigiam
nascentium_.
1661. Boyle's _Sceptical Chemist_. Passage of blood through
capillaries observed by Malpighi.
1665. Hooke's _Micrographia_.
1666. Académie des Sciences founded. Composition of white light
discovered by Newton.
1668. Redi on the Generation of Insects.
1669. Swammerdam's _Historia Insectorum Generalis_. Malpighi's _De
Bombyce_.
1671-1677. Grew's _Anatomy of Plants_; collected in one volume, 1682.
1672-1679. Malpighi's _Anatome Plantarum_; collected in his Opera
Omnia, 1686.
1673. Malpighi's _De formatione pulli in ovo_. Leeuwenhoek's first
paper published by the Royal Society.
1675. Greenwich Observatory founded. Velocity of light determined by
Roemer.
1676. Willughby's _Ornithologia_.
1677. Spermatozoa discovered by Hamm.
1680. Yeast-cells discovered by Leeuwenhoek.
1682. Ray's _Methodus Plantarum_.
1683. Bacteria discovered by Leeuwenhoek.
1687. Newton's _Principia_.
1691-1694. Camerarius on the sexes of flowering plants.
1702. Hydra discovered by Leeuwenhoek.
1711-1776. Hume.
1723-1790. Adam Smith.
1725. Vico's _Scienza Nuova_.
1734-1742. Réaumur's _Histoire des Insectes_.
1736-1810. Watt.
1737. Linnæus's _Systema Naturæ_; last edition by Linnæus, 1766.
Linnæus's _Genera Plantarum_.
1737-1738. Swammerdam's _Biblia Naturæ_ published; written long
before.
1738. Linnæus's _Classes Plantarum_.
1740-1761. Roesel von Rosenhof's _Insecten-Belustigungen_ begun.
1744. Trembley's _Polype d'eau douce_ (Hydra).
1745. Bonnet's _Traité d'Insectologie_ (aphids, Nais).
1748. Montesquieu's _Esprit des Lois_.
1749-1804. Buffon's _Histoire Naturelle_, the last volumes posthumous.
1752. Identity of lightning and electricity demonstrated by Franklin.
1753. British Museum founded.
1755. Black's experiments on carbonic acid and alkalis.
1759. C. F. Wolff's _Theoria Generationis_.
1760. Lyonet's _Traité Anatomique_, etc. (larva of goat-moth).
1770. New South Wales discovered by Captain Cook.
1775. Priestley's experiments on the restoration by green leaves
of air vitiated by combustion or respiration, and on
"dephlogisticated air" (oxygen). Adam Smith's _Wealth of Nations_.
1777. Spallanzani's experiments on the spontaneous generation of
minute organisms.
1781. Uranus discovered by Herschel. Leroy's _Lettres sur les Animaux_
(first collected edition).
1784. Cavendish's _Experiments on Air_ (composition of water).
1785. Hutton's _Theory of the Earth_.
1787-1789. Lavoisier's _Méthode de nomenclature chimique_ (1787) and
_Traité élémentaire de chimie_ (1789).
1789. First French Revolution. A. L. de Jussieu's _Genera Plantarum_.
White's _Natural History of Selborne_.
1790. Goethe's _Metamorphosen der Pflanzen_.
1791. Galvani's experiments on animal electricity.
1792. Sprengel's _Entdeckte Geheimniss der Natur_. F. Huber's
_Nouvelles Observations sur les Abeilles_.
1796. Cuvier on recent and fossil elephants.
1798. Jenner's _Inquiry_ (vaccination against small-pox). Lithography
invented by Senefelder.
1799. William Smith's _Order of the Strata and their Embedded Organic
Remains_.
1799-1825. Laplace's _Mécanique Celeste_.
1800. Volta's electric pile.
1807. Dalton's Atomic theory. Davy's decomposition of potash and soda.
1811. Motor and sensory roots of spinal nerves discovered by Bell.
1812. Cuvier's _Ossemens Fossiles_.
1816. Cuvier's _Règne Animal_.
1819. Electro-magnetism discovered by Œrsted. Chamisso's _De Salpa_.
1823-1831. Pollen-tubes traced to the ovule (Amici, Brongniart, Robert
Brown).
1827. Discovery of mammalian ovum by Baer.
1828-1837. Baer's _Entwickelungs-geschichte_.
1830-1832. Lyell's _Principles of Geology_.
1835. Cell-division in plants observed by Mohl.
1837. Caignard-Latour's demonstration that alcoholic fermentation is
due to living organisms.
1839. Schwann and Schleiden's cell-theory.
1840-1849. Joule's determination of the mechanical equivalent of heat.
1841. Faraday's discovery of electric induction.
1846. Discovery of Neptune by Leverrier and Adams. Agassiz and
Buckland's announcement of extensive glaciation in Scotland.
1848. Discovery of the antheridia of ferns by Suminsky.
1849-151. Hofmeister's comparative studies of the higher cryptogams
and the flowering plants.
1809-1851. Charles Darwin.
1822-1895. Louis Pasteur.
THE SUB-DIVISIONS OF BIOLOGY
Morphology:
Anatomy.
Minute Anatomy.
Comparative Anatomy.
Embryology.
Physiology (including adaptations to the conditions of life).
Psychology of Animals.
Classification.
Geographical Distribution.
Palæontology.
All these divisions, except Psychology, apply both to plants and
animals. Many other modes of division have been proposed.
BIBLIOGRAPHY
[It will be readily understood that the literature of Biology is
enormous, as a single fact will show. Half a century ago Dr. Hagen
compiled a list of books and papers relating to Entomology alone.
Though far from complete, it filled a thousand pages, and if brought
down to the present date would probably fill a thousand more. The
student who tries to follow in some detail the history of any branch of
Biology must read books in half-a-dozen languages, and work continually
in large public libraries. We shall attempt no more in this place than
to mention a few books which can be procured and read by those whose
leisure and knowledge of the subject are limited.]
History of Biology or its Sub-Divisions.
Carus, V. _Geschichte der Zoologie_. 1864 foll.
The French translation by Hagenmuller and Schneider (1880) will be
preferred by some.
Cuvier, G. _Histoire des Sciences Naturelles_. Publiée par M. de
Saint-Agy. Two vols., 1841. Taken down from Cuvier's lectures, but not
revised by him.
Though far from trustworthy (the first volume especially), this
history mentions many interesting facts, and suggests inquiries which
may be pursued with advantage.
Foster, Sir M. _Lectures on the History of Physiology_. Cambridge
Natural Science Manuals, 1901.
Green, J. R. _History of Botany_, 1860-1900. A continuation of
Sachs's History. Clarendon Press, 1909.
Sachs, J. _History of Botany_, 1530-60. English translation.
Clarendon Press, 1889.
An outline of the History of Palæontology is prefixed to Zittel's
_Handbuch der Palæontologie_, Bd. 1. (1876-80). English
translation, 1900-2.
The ninth edition of the _Encyclopædia Britannica_ often contains
useful references. See for example the articles Biology, Embryology,
Medicine, Parasitism, and Zoology.
Biographical dictionaries are of course indispensable. _The Dictionary
of National Biography_, the _Biographie_ _Universelle_, the
_Nouvelle Biographie Universelle_, the _Allgemeine Deutsche
Biographie_, and the _Biographie Nationale de Belgique_ will be
frequently consulted.
* * * * *
Among the old authors who can be read for pleasure as well as for
profit the present writer would include:—
Baker, H. _The Microscope Made Easy._ Second ed., 1743.—_Employment
for the Microscope._ 1753.
Belon, P. _Observations de plusieurs singularitez et choses mémorables
trouvées en Grece, Asie, Judée, Egypte, Arabie, et autres pays
estranges._ 1553.
—— _Histoire de la nature des Oyseaux._ 1555.
Buffon, Comte de. _Histoire Naturelle._ Forty-four vols., of which
thirty-six appeared during Buffon's lifetime. 1749-1804. Selected
passages only.
Cuvier, G. _Ossemens Fossiles._ 1812. Fourth ed. in ten vols., besides
two of plates, 1834-36. Selected passages only.
Hooke, R. _Micrographia._ 1665.
Huber, F. _Nouvelles observations sur les Abeilles._ 1792. Second ed.,
two vols., 1814.
—— J. P. _Recherches sur les mœurs des Fourmis indigènes._ 1810.
Le Roy, G. _Lettres sur les Animaux._ 1781. Reprinted, 1862.
Linnæus, C., and his Pupils. _Amœnitates Academicæ._ Seven vols.,
1749-69.
Contain interesting discussions here and there among much that is now
valueless.
—— _Lachesis Lapponica; or, A Tour in Lapland._ Translated by Sir J.
E. Smith from the original diary. Two vols., 1811.
Ray, J. _Catalogus Plantarum circa Cantabrigiam nascentium._ 1660.
Réaumur, R. A. F. de. _Histoire des Insectes._ Six vols. 1734-42.
Redi, F. _Experiments on the Generation of Insects._ Translated from
the Italian edition of 1688 by Mab Bigelow. Chicago, 1909.
Roesel von Rosenhof, A. J. _Insecten-belustigungen._ 1746-61.
Turner, W. _On Birds._ 1544. Translated by A. H. Evans, 1903.
INDEX
AFFINITY, 17, 51
Agassiz, 122
Albrecht, 61
Aldrovandi, 13
America, discovery of, 24, 112