_After Aristotle_
All Aristotle's surviving biological works refer primarily to the animal
creation. His work on plants is lost or rather has survived as the
merest corrupted fragment. We are fortunate, however, in the possession
of a couple of complete works by his pupil and successor Theophrastus
(372-287), which may not only be taken to represent the Aristotelian
attitude towards the plant world, but also give us an inkling of the
general state of biological science in the generation which succeeded
the master.
[Illustration: Fig. 7. ARISTOTLE
From HERCULANEUM
Probably work of fourth century B. C.]
These treatises of Theophrastus are in many respects the most complete
and orderly of all ancient biological works that have reached our time.
They give an idea of the kind of interest that the working scientist of
that day could develop when inspired rather by the genius of a great
teacher than by the power of his own thoughts. Theophrastus is a
pedestrian where Aristotle is a creature of wings, he is in a relation
to the master of the same order that the morphologists of the second
half of the nineteenth century were to Darwin. For a couple of
generations after the appearance of the _Origin of Species_ in 1859 the
industry and ability of naturalists all over the world were occupied in
working out in detail the structure and mode of life of living things
on the basis of the Evolutionary philosophy. Nearly all the work on
morphology and much of that on physiology since his time might be
treated as a commentary on the works of Darwin. These volumes of
Theophrastus give the same impression. They represent the remains--alas,
almost the only biological remains--of a school working under the
impulse of a great idea and spurred by the memory of a great teacher. As
such they afford a parallel to much scientific work of our own day,
produced by men without genius save that provided by a vision and a hope
and an ideal. Of such men it is impossible to write as of Aristotle.
Their lives are summed up by their actual achievement, and since
Theophrastus is an orderly writer whose works have descended to us in
good state, he is a very suitable instance of the actual standard of
achievement of ancient biology. 'Without vision the people perish' and
the very breath of life of science is drawn, and can only be drawn, from
that very small band of prophets who from time to time, during the ages,
have provided the great generalizations and the great ideals. In this
light let us examine the work of Theophrastus.
In the absence of any adequate system of classification, almost all
botany until the seventeenth century consisted mainly of descriptions of
species. To describe accurately a leaf or a root in the language in
ordinary use would often take pages. Modern botanists have invented an
elaborate terminology which, however hideous to eye and ear, has the
crowning merit of helping to abbreviate scientific literature. Botanical
writers previous to the seventeenth century were substantially without
this special mode of expression. It is partly to this lack that we owe
the persistent attempts throughout the centuries to represent plants
pictorially in herbals, manuscript and printed, and thus the possibility
of an adequate history of plant illustration.
Theophrastus seems to have felt acutely the need of botanical terms,
and there are cases in which he seeks to give a special technical
meaning to words in more or less current use. Among such words are
_carpos_ = fruit, _pericarpion_ = seed vessel = pericarp, and _metra_,
the word used by him for the central core of any stem whether formed of
wood, pith, or other substance. It is from the usage of Theophrastus
that the exact definition of fruit and pericarp has come down to us.[18]
We may easily discern also the purpose for which he introduces into
botany the term _metra_, a word meaning primarily the _womb_, and the
vacancy in the Greek language which it was made to fill. '_Metra_,' he
says, 'is that which is in the middle of the wood, being third in order
from the bark and [thus] like to the marrow in bones. Some call it the
_heart_ (καρδιαν {kardian}), others the _inside_ (εντεριωνην
{enteriônên}), yet others call only the innermost part of the metra
itself the heart, while others again call this _marrow_.'[19] He is thus
inventing a word to cover all the different kinds of core and importing
it from another study. This is the method of modern scientific
nomenclature which hardly existed for botanists even as late as the
sixteenth century of our era. The real foundations of our modern
nomenclature were laid in the later sixteenth and in the seventeenth
century by Cesalpino and Joachim Jung.
[18] It is possible that Theophrastus derived the word pericarp from
Aristotle. Cp. _De anima_, ii. 1, 412 b 2. In the passage το φυλλον
περικαρπιου σκεπασμα, το δε περικαρπιον καρπου {to phyllon
perikarpiou skepasma, to de perikarpion karpou}, in the _De anima_
the word does not, however, seem to have the full technical force
that Theophrastus gives to it.
[19] _Historia plantarum_, i. 2, vi.
Theophrastus understood the value of developmental study, a conception
derived from his master. 'A plant', he says, 'has power of germination
in all its parts, for it has life in them all, wherefore we should
regard them not for what they are but for what they are becoming.'[20]
The various modes of plant reproduction are correctly distinguished in a
way that passes beyond the only surviving earlier treatise that deals
in detail with the subject, the Hippocratic work _On generation_. 'The
manner of generation of trees and plants are these: spontaneous, from a
seed, from a root, from a piece torn off, from a branch or twig, from
the trunk itself, or from pieces of the wood cut up small.'[21] The
marvel of germination must have awakened admiration from a very early
date. We have already seen it occupying a more ancient author, and it
had also been one of the chief preoccupations of Aristotle. It is thus
not remarkable that the process should impress Theophrastus, who has
left on record his views on the formation of the plant from the seed.
[20] _Ibid._ i. 1, iv.
[21] _Historia plantarum_, ii. 1, i.
'Some germinate, root and leaves, from the same point, some
separately from either end of the seed. Thus wheat, barley, spelt,
and all such cereals [germinate] from either end, corresponding to
the position [of the seed] in the ear, the root from the stout
lower part, the shoot from the upper; but the two, root and stem,
form a single continuous whole. The bean and other leguminous
plants are not so, but in them root and stem are from the same
point, namely, their place of attachment to the pod, where, it is
plain, they have their origin. In some cases there is a process, as
in beans, chick peas, and especially lupines, from which the root
grows downward, the leaf and stem upward.... In certain trees the
bud first germinates within the seed, and, as it increases in size,
the seeds split--all such seeds are, as it were, in two halves;
again, all those of leguminous plants have plainly two lobes and
are double--and then the root is immediately thrust out. But in
cereals, the seeds being in one piece, this does not happen, but
the root grows a little before [the shoot].
'Barley and wheat come up monophyllous, but peas, beans, and chick
peas polyphyllous. All leguminous plants have a single woody root,
from which grow slender side roots ... but wheat, barley, and the
other cereals have numerous slender roots by which they are matted
together.... There is a contrast between these two kinds; the
leguminous plants have a single root and have many side-growths
above from the [single] stem ... while the cereals have many roots
and send up many shoots, but these have no side-shoots.'[22]
[22] _Historia plantarum_, viii. 1, i.
There can be no doubt that here is a piece of minute observation on the
behaviour of germinating seeds. The distinction between dicotyledons and
monocotyledons is accurately set forth, though the stress is laid not so
much on the cotyledonous character of the seed as on the relation of
root and shoot. In the dicotyledons root and shoot are represented as
springing from the same point, and in monocotyledons from opposite poles
in the seed.
No further effective work was done on the germinating seed until the
invention of the microscope, and the appearance of the work of Highmore
(1613-85),[23] and the much more searching investigations of Malpighi
(1628-94)[24] and Grew (1641-1712)[25] after the middle of the
seventeenth century. The observations of Theophrastus are, however, so
accurate, so lucid, and so complete that they might well be used as
legends for the plates of these writers two thousand years after him.
[23] Nathaniel Highmore, _A History of Generation_, London, 1651.
[24] Marcello Malpighi, _Anatome plantarum_, London, 1675.
[25] Nehemiah Grew, _Anatomy of Vegetables begun_, London, 1672.
Much has been written as to the knowledge of the sex of plants among the
ancients. It may be stated that of the sexual elements of the flower no
ancient writer had any clear idea. Nevertheless, sex is often attributed
to plants, and the simile of the _Loves of Plants_ enters into works of
the poets. Plants are frequently described as male and female in ancient
biological writings also, and Pliny goes so far as to say that some
students considered that all herbs and trees were sexual.[26] Yet when
such passages can be tested it will be found that these so-called males
and females are usually different species. In a few cases a sterile
variety is described as the male and a fertile as the female. In a small
residuum of cases diœcious plants or flowers are regarded as male and
female, but with no real comprehension of the sexual nature of the
flowers. There remain the palms, in which the knowledge of plant sex had
advanced a trifle farther. 'With dates', says Theophrastus, 'the males
should be brought to the females; for the males make the fruit persist
and ripen, and this some call by analogy _to use the wild fig_
(ολυνθαζειν {olynthazein}).[27] The process is thus: when the male is in
the flower they at once cut off the spathe with the flower and shake the
bloom, with its flower and dust, over the fruit of the female, and, if
it is thus treated, it retains the fruit and does not shed it.'[28] The
fertilizing character of the spathe of the male date palm was familiar
in Babylon from a very early date. It is recorded by Herodotus[29] and
is represented by a frequent symbol on the Assyrian monuments.
[26] Pliny, _Naturalis historia_, xiii. 4.
[27] The curious word ολυνθαζειν {olynthazein}, here translated _to
use the wild fig_, is from ολυνθος {olynthos}, a kind of wild fig
which seldom ripens. The special meaning here given to the word is
explained in another work of Theophrastus, _De causis plantarum_,
ii. 9, xv. After describing caprification in figs, he says το δε επι
των φοινικων συμβαινον ου ταυτον μεν, εχει δε τινα ὁμοιοτητα τουτω
δι' ὁ καλουσιν ολυνθαζειν αυτους {to de epi tôn phoinikôn symbainon
ou tauton men, echei de tina homoiotêta toutô di' ho kalousin
olynthazein autous} 'The same thing is not done with dates, but
something analogous to it, whence this is called ολυνθαζειν'
{olynthazein'}.
[28] _Historia plantarum_, ii. 8, iv.
[29] Herodotus i. 193.
The comparison of the fertilization of the date palm to the use of the
wild fig refers to the practice of Caprification. Theophrastus tells us
that there are certain trees, the fig among them, which are apt to shed
their fruit prematurely. To remedy this 'the device adopted is
caprification. Gall insects come out of the wild figs which are hanging
there, eat the tops of the cultivated figs, and so make them swell'.[30]
These gall-insects 'are engendered from the seeds'.[31] Theophrastus
distinguished between the process as applied to the fig and the date,
observing that 'in both [fig and date] the male aids the female--for
they call the fruit-bearing [palm] _female_--but whilst in the one there
is a union of the two sexes, in the other things are different'.[32]
[30] _Historia plantarum_, ii. 8, i.
[31] _Ibid._ ii. 8, ii.
[32] _Historia plantarum_, ii. 8, iv.
Theophrastus was not very successful in distinguishing the nature of the
primary elements of plants, though he was able to separate root, stem,
leaf, stipule, and flower on morphological as well as to a limited
extent on physiological grounds. For the root he adopts the familiar
definition, the only one possible before the rise of chemistry, that it
'is that by which the plant draws up nourishment',[33] a description
that applies to the account given by the pre-Aristotelian author of the
work περι γονης {peri gonês}, _On generation_. But Theophrastus shows by
many examples that he is capable of following out morphological
homologies. Thus he knows that the ivy regularly puts forth roots from
the shoots between the leaves, by means of which it gets hold of trees
and walls,[34] that the mistletoe will not sprout except on the bark of
living trees into which it strikes its roots, and that the very peculiar
formation of the mangrove tree is to be explained by the fact that 'this
plant sends out roots from the shoots till it has hold on the ground and
roots again: and so there comes to be a continuous circle of roots round
the tree, not connected with the main stem, but at a distance from
it'.[35] He does not succeed, however, in distinguishing the real nature
of such structures as bulbs, rhizomes, and tubers, but regards them all
as roots. Nor is he more successful in his discussion of the nature of
stems. As to leaves, he is more definite and satisfactory, though wholly
in the dark as to their function; he is quite clear that the pinnate
leaf of the rowan tree, for instance, is a leaf and not a branch.
[33] _Ibid._ i. 1, ix.
[34] _Ibid._ iii. 18, x.
[35] _De causis plantarum_, ii. 23.
Notwithstanding his lack of insight as to the nature of sex in flowers,
he attains to an approximately correct idea of the relation of flower
and fruit. Some plants, he says, 'have [the flower] around the fruit
itself as vine and olive; [the flowers] of the latter, when they drop,
look as though they had a hole through them, and this is taken for a
sign that it has blossomed well; for if [the flower] is burnt up or
sodden, the fruit falls with it, and so it does not become pierced. Most
flowers have the fruit case in the middle, or it may be the flower is on
the top of the pericarp as in pomegranate, apple, pear, plum, and myrtle
... for these have their seeds below the flower.... In some cases again
the flower is on top of the seeds themselves as in ... all thistle-like
plants'.[36] Thus Theophrastus has succeeded in distinguishing between
the hypogynous, perigynous, and epigynous types of flower, and has
almost come to regard its relation to the fruit as the essential floral
element.
[36] _Historia plantarum_, i. 13, iii.
[Illustration: Fig. 8. THEOPHRASTUS
From VILLA ALBANI
Copy (second century A. D.?) of earlier work]
Theophrastus has a perfectly clear idea of plant distribution as
dependent on soil and climate, and at times seems to be on the point of
passing from a statement of climatic distribution into one of real
geographical regions. The general question of plant distribution long
remained at, if it did not recede from, the position where he left it.
The usefulness of the manuscript and early printed herbals in the West
was for centuries marred by the retention of plant descriptions prepared
for the Greek East and Latin South, and these works were saved from
complete ineffectiveness only by an occasional appeal to nature.
With the death of Theophrastus about 287 B. C. pure biological science
substantially disappears from the Greek world, and we get the same type
of deterioration that is later encountered in other scientific
departments. Science ceases to have the motive of the desire to know,
and becomes an applied study, subservient to the practical arts. It is
an attitude from which in the end applied science itself must suffer
also. Yet the centuries that follow were not without biological writers
of very great ability. In the medical school of Alexandria anatomy and
physiology became placed on a firm basis from about 300 B. C., but
always in the position subordinate to medicine that they have since
occupied. Two great names of that school, Herophilus and Erasistratus,
we must consider elsewhere.[37] Their works have disappeared and we have
the merest fragments of them. In the last pre-Christian and the first
two post-Christian centuries, however, there were several writers,
portions of whose works have survived and are of great biological
importance. Among them we include Crateuas, a botanical writer and
illustrator, who greatly developed, if he did not actually introduce,
the method of representing plants systematically by illustration rather
than by description. This method, important still, was even more
important when there was no proper system of botanical nomenclature.
Crateuas by his paintings of plants, copies of which have not improbably
descended to our time, began a tradition which, fixed about the fifth
century, remained almost rigid until the re-discovery of nature in the
sixteenth. He was physician to Mithridates VI Eupator (120-63 B. C.),
but his work was well known and appreciated at Rome, which became the
place of resort for Greek talent.[38]
[37] See the companion chapter on _Greek Medicine_.
[38] The surviving fragments of the works of Crateuas have recently
been printed by M. Wellmann as an appendix to the text of
Dioscorides, _De materia medica_, 3 vols., Berlin, 1906-17, iii. pp.
144-6. The source and fate of his plant drawings are discussed in
the same author's _Krateuas_, Berlin, 1897.
Celsus, who flourished about 20 B. C., wrote an excellent work on
medicine, but gives all too little glimpse of anatomy and physiology.
Rufus of Ephesus, however, in the next century practised dissection of
apes and other animals. He described the decussation of the optic nerves
and the capsule of the crystalline lens, and gave the first clear
description that has survived of the structure of the eye. He regarded
the nerves as originating from the brain, and distinguished between
nerves of motion and of sensation. He described the oviduct of the sheep
and rightly held that life was possible without the spleen.
The second Christian century brings us two writers who, while
scientifically inconsiderable, acted as the main carriers of such
tradition of Greek biology as reached the Middle Ages, Pliny and
Dioscorides. Pliny (A. D. 23-79), though a Latin, owes almost everything
of value in his encyclopaedia to Greek writings. In his _Natural
History_ we have a collection of current views on the nature, origin,
and uses of plants and animals such as we might expect from an
intelligent, industrious, and honest member of the landed class who was
devoid of critical or special scientific skill. Scientifically the work
is contemptible, but it demands mention in any study of the legacy of
Greece, since it was, for centuries, a main conduit of the ancient
teaching and observations on natural history. Read throughout the ages,
alike in the darkest as in the more enlightened periods, copied and
recopied, translated, commented on, extracted and abridged, a large part
of Pliny's work has gradually passed into folk-keeping, so that through
its agency the gipsy fortune-teller of to-day is still reciting garbled
versions of the formulae of Aristotle and Hippocrates of two and a half
millennia ago.
The fate of Dioscorides (flourished A. D. 60) has been not dissimilar.
His work _On Materia Medica_ consists of a series of short accounts of
plants, arranged almost without reference to the nature of the plants
themselves, but quite invaluable for its terse and striking descriptions
which often include habits and habitats. Its history has shown it to be
one of the most influential botanical treatises ever penned. It provided
most of the little botanical knowledge that reached the Middle Ages. It
furnished the chief stimulus to botanical research at the time of the
Renaissance. It has decided the general form of every modern
pharmacopœia. It has practically determined modern plant nomenclature
both popular and scientific.
Translated into nearly every language from Anglo-Saxon and Bohemian to
Arabic and Hebrew, appearing both abstracted and in full in innumerable
beautifully illuminated manuscripts, some of which are still among the
fairest treasures of the great national libraries, Dioscorides, the
drug-monger, appealed to scholasticized minds for centuries. The
frequency with which fragments of him are encountered in papyri shows
how popular his work was in Egypt in the third and fourth centuries. One
of the earliest datable Greek codices in existence is a glorious volume
of Dioscorides written in capitals,[39] thought worthy to form a wedding
gift for a lady who was the daughter of one Roman emperor and the
betrothed of a second.[40] The illustrations of this fifth-century
manuscript are a very valuable monument for the history of art and the
chief adornment of what was once the Royal Library at Vienna[41] (figs.
9-10). Illustrated Latin translations of Dioscorides were in use in the
time of Cassiodorus (490-585). A work based on it, similarly
illustrated, but bearing the name of Apuleius, is among the most
frequent of mediaeval botanical documents and the earliest surviving
specimen is contemporary with Cassiodorus himself.[42] After the
revival of learning Dioscorides continued to attract an immense amount
of philological and botanical ability, and scores of editions of his
works, many of them nobly illustrated, poured out of the presses of the
sixteenth and seventeenth centuries.
[Illustration: Fig. 9
ΣΟΓΚΟΣ ΤΡΥΦΕΡΟΣ {SOGKOS TRYPHEROS} = _Crepis paludosa_, _Mœn._]
[Illustration: Fig. 10
ΓΕΡΑΝΙΟΝ {GERANION} = _Geranium pyrenaicum_, _L._
Fifth-century drawings from JULIANA ANICIA M.S., copied from originals
of first century B. C. (?)]
[39] The manuscript in question is Med. Graec. 1 at what was the
Royal Library at Vienna. It is known as the _Constantinopolitanus_.
After the war it was taken to St. Mark's at Venice, but either has
been or is about to be restored to Vienna. A facsimile of this grand
manuscript was published by Sijthoff, Leyden, 1906.
[40] The lady in question was Juliana Anicia, daughter of Anicius
Olybrius, Emperor of the West in 472, and his wife Placidia,
daughter of Valentinian III. Juliana was betrothed in 479 by the
Eastern Emperor Zeno to Theodoric the Ostrogoth, but was married,
probably in 487 when the manuscript was presented to her, to
Areobindus, a high military officer under the Byzantine Emperor
Anastasius.
[41] The importance of this manuscript as well as the position of
Dioscorides as medical botanist is discussed by Charles Singer in an
article 'Greek Biology and the Rise of Modern Biology', _Studies in
the History and Method of Science_, vol. ii, Oxford, 1921.
[42] This manuscript is at the University Library at Leyden, where
it is numbered Voss Q 9.
But the greatest biologist of the late Greek period, and indeed one of
the greatest biologists of all time, was Claudius Galen of Pergamon (A.
D. 131-201). Galen devoted himself to medicine from an early age, and in
his twenty-first year we hear of him studying anatomy at Smyrna under
Pelops. With the object of extending his knowledge of drugs he early
made long journeys to Asia Minor. Later he proceeded to Alexandria,
where he improved his anatomical equipment, and here, he tells us, he
examined a human skeleton. It is indeed probable that his direct
practical acquaintance with human anatomy was limited to the skeleton
and that dissection of the human body was no longer carried on at
Alexandria in his time. Thus his physiology and anatomy had to be
derived mainly from animal sources. He is the most voluminous of all
ancient scientific writers and one of the most voluminous writers of
antiquity in any department. We are not here concerned with the medical
material which mainly fills these huge volumes, but only with the
physiological views which not only prevailed in medicine until Harvey
and after, but also governed for fifteen hundred years alike the
scientific and the popular ideas on the nature and workings of the
animal body, and have for centuries been embedded in our speech. A
knowledge of these physiological views of Galen is necessary for any
understanding of the history of biology and illuminates many literary
allusions of the Middle Ages and Renaissance.
Between the foundation of the Alexandrian school and the time of Galen,
medicine was divided among a great number of sects. Galen was an
eclectic and took portions of his teaching from many of these schools,
but he was also a naturalist of great ability and industry, and knew
well the value of the experimental way. Yet he was a somewhat windy
philosopher and, priding himself on his philosophic powers, did not
hesitate to draw conclusions from evidence which was by no means always
adequate. The physiological system that he thus succeeded in building up
we may now briefly consider (fig. 11).
[Illustration: FIG. 11. Illustrating Galen's physiological teaching.]
The basic principle of life, in the Galenic physiology, is a _spirit_,
_anima_ or _pneuma_, drawn from the general world-soul in the act of
respiration. It enters the body through the _rough artery_ (τραχεια
αρτηρια {tracheia artêria}, _arteria aspera_ of mediaeval notation), the
organ known to our nomenclature as the trachea. From this trachea the
pneuma passes to the lung and then, through the _vein-like artery_
(αρτηρια φλεβωδης {artêria phlebôdês}, _arteria venalis_ of mediaeval
writers, the pulmonary vein of our nomenclature), to the left ventricle.
Here it will be best to leave it for a moment and trace the vascular
system along a different route.
Ingested food, passing down the alimentary tract, was absorbed as chyle
from the intestine, collected by the portal vessel, and conveyed by it
to the liver. That organ, the site of the innate heat in Galen's view,
had the power of elaborating the chyle into venous blood and of imbuing
it with a spirit or pneuma which is innate in all living substance, so
long as it remains alive, the _natural spirits_ (πνευμα φυσικον {pneuma
physikon}, _spiritus naturalis_ of the mediaevals). Charged with this,
and also with the nutritive material derived from the food, the venous
blood is distributed by the liver through the veins which arise from it
in the same way as the arteries from the heart. These veins carry
nourishment and _natural spirits_ to all parts of the body. _Iecur fons
venarum_, the liver as the source of the veins, remained through the
centuries the watchword of the Galenic physiology. The blood was held to
ebb and flow continuously in the veins during life.
Now from the liver arose one great vessel, the hepatic vein, from
division of which the others were held to come off as branches. Of
these branches, one, our _common vena cava_, entered the right side of
the heart. For the blood that it conveyed to the heart there were two
fates possible. The greater part remained awhile in the ventricle,
parting with its impurities and vapours, exhalations of the organs,
which were carried off by the _artery-like vein_ (φλεπς αρτηριωδης
{phleps artêriôdês}, the mediaeval _vena arterialis_, our pulmonary
artery) to the lung and then exhaled to the outer air. These impurities
and vapours gave its poisonous and suffocating character to the breath.
Having parted thus with its impurities, the venous blood ebbed back
again from the right ventricle into the venous system. But for a small
fraction of the venous blood that entered the right ventricle another
fate was reserved. This small fraction of venous blood, charged still
with the _natural spirits_ derived from the liver, passed through minute
channels in the septum between the ventricles and entered the left
chamber. Arrived there, it encountered the external pneuma and became
thereby elaborated into a higher form of spirit, the _vital spirits_
(πνευμα ζωτικον {pneuma zôtikon}, _spiritus vitalis_), which is
distributed together with blood by the arterial system to various parts
of the body. In the arterial system it also ebbed and flowed, and might
be seen and felt to pulsate there.
But among the great arterial vessels that sent forth arterial blood thus
charged with vital spirits were certain vessels which ascended to the
brain. Before reaching that organ they divided up into minute channels,
the _rete mirabile_ (πλεγμα μεγιστον θαυμα {plegma megiston thauma}),
and passing into the brain became converted by the action of that organ
into a yet higher type of spirits, the _animal spirits_ (πνευμα ψυχικον
{pneuma psychikon}, _spiritus animalis_), an ethereal substance
distributed to the various parts of the body by the structures known
to-day as nerves, but believed then to be hollow channels. The three
fundamental faculties (δυναμεις {dynameis}), the _natural_, the _vital_,
and the _animal_, which brought into action the corresponding functions
of the body, thus originated as an expression of the primal force or
pneuma.
This physiology, we may emphasize, is not derived from an investigation
of human anatomy. In the human brain there is no _rete mirabile_, though
such an organ is found in the calf. In the human liver there is no
_hepatic vein_, though such an organ is found in the dog. Dogs, calves,
pigs, bears, and, above all, Barbary apes were freely dissected by Galen
and were the creatures from which he derived his physiological ideas.
Many of Galen's anatomical and physiological errors are due to his
attributing to one creature the structures found in another, a fact that
only very gradually dawned on the Renaissance anatomists.
The whole knowledge possessed by the world in the department of
physiology from the third to the seventeenth century, nearly all the
biological conceptions till the thirteenth, and most of the anatomy and
much of the botany until the sixteenth century, all the ideas of the
physical structure of living things throughout the Middle Ages, were
contained in a small number of these works of Galen. The biological
works of Aristotle and Theophrastus lingered precariously in a few rare
manuscripts in the monasteries of the East; the total output of hundreds
of years of Alexandrian and Pergamenian activities was utterly
destroyed; the Ionian biological works, of which a sample has by a
miracle survived, were forgotten; but these vast, windy, ill-arranged
treatises of Galen lingered on. Translated into Latin, Syriac, Arabic,
and Hebrew, they saturated the intellectual world of the Middle Ages.
Commented on by later Greek writers, who were themselves in turn
translated into the same list of languages, they were yet again served
up under the names of such Greek writers as Oribasius, Paul of Aegina,
or Alexander of Tralles.
What is the secret of the vitality of these Galenic biological
conceptions? The answer can be given in four words. _Galen is a
teleologist_; and a teleologist of a kind whose views happened to fit in
with the prevailing theological attitude of the Middle Ages, whether
Christian, Moslem, or Jewish. According to him everything which exists
and displays activity in the human body originates in and is formed by
an intelligent being and on an intelligent plan, so that the organ in
structure and function is the result of that plan. 'It was the Creator's
infinite wisdom which selected the best means to attain his beneficent
ends, and it is a proof of His omnipotence that he created every good
thing according to His design, and thereby fulfilled His will.'[43]
[43] A good instance of Galen's teleological point of view is
afforded by his classical description of _the hand_ in the περι
χρειας των εν ανθρωπου σωματι μοριων {peri chreias tôn en anthrôpou
sômati moriôn}, _On the uses of the parts of the body of man_, i. 1.
This passage is available in English in a tract by Thomas Bellott,
London, 1840.
After Galen there is a thousand years of darkness, and biology ceases to
have a history. The mind of the Dark Ages turned towards theology, and
such remains of Neoplatonic philosophy as were absorbed into the
religious system were little likely to be of aid to the scientific
attitude. One department of positive knowledge must of course persist.
Men still suffered from the infirmities of the flesh and still sought
relief from them. But the books from which that advice was sought had
nothing to do with general principles nor with knowledge as such. They
were the most wretched of the treatises that still masqueraded under the
names of Hippocrates and Galen, mostly mere formularies, antidotaries,
or perhaps at best symptom lists. And, when the depression of the
western intellect had passed its worst, there was still no biological
material on which it could be nourished.
The prevailing interest of the barbarian world, at last beginning to
settle into its heritage of antiquity, was with Logic. Of Aristotle
there survived in Latin dress only the _Categories_ and the _De
interpretatione_, the merciful legacy of Boethius, the last of the
philosophers. Had a translation of Aristotle's _Historia animalium_ or
_De generatione animalium_ survived, had a Latin version of the
Hippocratic work _On generation_ or of the treatises of Theophrastus _On
plants_ reached the earlier Middle Ages, the whole mental history of
Europe might have been different and the rediscovery of nature might
have been antedated by centuries. But this was a change of heart for
which the world had long to wait; something much less was the earliest
biological gift of Greece. The gift, when it came, came in two forms,
one of which has not been adequately recognized, but both are equally
her legacy. These two forms are, firstly, the well-known work of the
early translators and, secondly, the tardily recognized work of certain
schools of minor art.
The earliest biological treatises to become accessible in the west were
rendered not from Greek but from Arabic.[44] The first of them was
perhaps the treatise περι μυων κινησεως {peri myôn kinêseôs}, _On
movement of muscles_ of Galen, a work which contains more than its title
suggests and indeed sets forth much of the Galenic physiological system.
It was rendered into Latin from the Arabic of Joannitius (Hunain ibn
Ishaq, 809-73), probably about the year 1200, by one Mark of Toledo. It
attracted little attention, but very soon after biological works of
Aristotle began to become accessible. The first was probably the
fragment _On plants_. The Greek original of this is lost, and besides
the Latin, only an Arabic version of a former Arabic translation of a
Syriac rendering of a Greek commentary is now known! Such a work
appeared from the hand of a translator known as Alfred the Englishman
about 1220 or a little later. Neither it nor another work from the same
translator, _On the motion of the heart_, which sought to establish the
primacy of that organ on Aristotelian grounds, can be said to contain
any of the spirit of the master.[45]
[44] The early European translations from the Arabic are tabulated
with unparalleled learning by M. Steinschneider, 'Die Europäischen
Uebersetzungen aus dem Arabischen bis Mitte des 17. Jahrhunderts',
in the _Sitzungsberichte der kais. Akad. der Wissenschaften in
Wien_, cxlix and cli, Vienna, 1904 and 1905.
[45] C. H. Haskins, 'The reception of Arabic science in England,'
_English Historical Review_, London, 1915, p. 56.
A little better than these is the work of the wizard Michael the Scot
(1175?-1234?). Roger Bacon tells us that Michael in 1230 'appeared [at
Oxford], bringing with him the works of Aristotle in natural history and
mathematics, with wise expositors, so that the philosophy of Aristotle
was magnified among the Latins'.[46] Scott produced his work _De
animalibus_ about this date and he included in it the three great
biological works of Aristotle, all rendered from an inferior Arabic
version.[47] Albertus Magnus (1206-80) had not as yet a translation
direct from the Greek to go upon for his great commentary on the
_History of animals_, but he depended on Scott. The biological works of
Aristotle were rendered into Latin direct from the Greek in the year
1260 probably by William of Moerbeke.[48] Such translations, appearing
in the full scholastic age when everything was against direct
observation, cannot be said to have fallen on a fertile ground. They
presented an ordered account of nature and a good method of
investigation, but those were gifts to a society that knew little of
their real value.[49]
[46] Roger Bacon, _Opus majus_, edited by J. H. Bridges, 3 vols.,
London, 1897-1900. Vol. iii, p. 66.
[47] On the Aristotelian translations of Scott see A. H. Querfeld,
_Michael Scottus und seine Schrift, De secretis naturae_, Leipzig,
1919; and C. H. Haskins, 'Michael Scot and Frederick II' in _Isis_,
ii. 250, Brussels, 1922.
[48] J. G. Schneider, _Aristotelis de animalibus historiae_,
Leipzig, 1811, p. cxxvi. L. Dittmeyer, _Guilelmi Moerbekensis
translatio commentationis Aristotelicae de generatione animalium_,
Dillingen, 1915. L. Dittmeyer, _De animalibus historia_, Leipzig,
1907.
[49] The subject of the Latin translations of Aristotle is traversed
by A. and C. Jourdain, _Recherches critiques sur l'âge des
traductions latines d'Aristote_, 2nd ed., Paris, 1843; M. Grabmann,
_Forschungen uber die lateinischen Aristoteles Ubersetzungen des
XIII. Jahrhunderts_, Münster i/W., 1916; and F. Wüstenfeld, _Die
Ubersetzungen arabischer Werke in das Lateinische seit dem XI.
Jahrhundert_, Göttingen, 1877.
Yet the advent of these texts was coincident with a returning desire to
observe nature. Albert, with all his scholasticism, was no contemptible
naturalist. He may be said to have begun first-hand plant study in
modern times so far as literary records are concerned. His book _De
vegetabilibus_ contains excellent observations, and he is worthy of
inclusion among the fathers of botany. In his vast treatise _De
animalibus_, hampered as he is by his learning and verbosity, he shows
himself a true observer and one who has absorbed something of the spirit
of the great naturalist to whose works he had devoted a lifetime of
study and on which he professes to be commenting. We see clearly the
leaven of the Aristotelian spirit working, though Albert is still a
schoolman. We may select for quotation a passage on the generation of
fish, a subject on which some of Aristotle's most remarkable
descriptions remained unconfirmed till modern times. These descriptions
impressed Albert in the same way as they do the modern naturalist. To
those who know nothing of the stimulating power of the Aristotelian
biological works, Albert's description of the embryos of fish and his
accurate distinction of their mode of development from that of birds, by
the absence of an allantoic membrane in the one and its presence in the
other, must surely be startling. Albert depends on Aristotle--a
third-hand version of Aristotle--but does not slavishly follow him.
'Between the mode of development (_anathomiam generationis_) of birds'
and fishes' eggs there is this difference: during the development of the
fish the second of the two veins which extend from the heart [as
described by Aristotle in birds] does not exist. For we do not find the
vein which extends to the outer covering in the eggs of birds which some
wrongly call the navel because it carries the blood to the exterior
parts; but we do find the vein that corresponds to the yolk vein of
birds, for this vein imbibes the nourishment by which the limbs
increase.... In fishes as in birds, channels extend from the heart first
to the head and the eyes, and first in them appear the great upper
parts. As the growth of the young fish increases the albumen decreases,
being incorporated into the members of the young fish, and it disappears
entirely when development and formation are complete. The beating of
the heart ... is conveyed to the lower part of the belly, carrying pulse
and life to the inferior members.
'While the young [fish] are small and not yet fully developed they have
veins of great length which take the place of the navel-string, but as
they grow and develop, these shorten and contract into the body towards
the heart, as we have said about birds. The young fish and the eggs are
enclosed and in a covering, as are the eggs and young of birds. This
covering resembles the dura mater [of the brain], and beneath it is
another [corresponding therefore to the pia mater of the brain] which
contains the young animal and nothing else.'[50]
[50] The enormous _De Animalibus_ of Albert of Cologne is now
available in an edition by H. Stadler, _Albertus Magnus De
Animalibus Libri XXVI nach der cölner Urschrift_, 2 vols., Münster
i/W., 1916-21. The quotation is translated from vol. i, pp. 465-6.
In the next century Conrad von Megenberg (1309-98) produced his _Book of
Nature_, a complete work on natural history, the first of the kind in
the vernacular, founded on Latin versions, now rendered direct from the
Greek, of the Aristotelian and Galenic biological works. It is well
ordered and opens with a systematic account of the structure and
physiology of man as a type of the animal creation, which is then
systematically described and followed by an account of plants. Conrad,
though guided by Aristotle, uses his own eyes and ears, and with him and
Albert the era of direct observation has begun.[51]
[51] Conrad's work is conveniently edited by H. Schultz, _Das Buch
der Natur von Conrad von Megenberg, die erste Naturgeschichte in
deutscher Sprache, in Neu-Hochdeutsche Sprache bearbeitet_,
Greifswald, 1897. Conrad's work is based on that of Thomas of
Cantimpré (1201-70).
But there was another department in which the legacy of Greece found an
even earlier appreciation. For centuries the illustrations to herbals
and bestiaries had been copied from hand to hand, continuing a tradition
that had its rise with Greek artists of the first century B. C. But
their work, copied at each stage without reference to the object, moved
constantly farther from resemblance to the original. At last the
illustrations became little but formal patterns, a state in which they
remained in some late copies prepared as recently as the sixteenth
century. But at a certain period a change set in, and the artist, no
longer content to rely on tradition, appeals at last to nature. This new
stirring in art corresponds with the new stirring in letters, the
Arabian revival--itself a legacy of Greece, though sadly deteriorated in
transit--that gave rise to scholasticism. In much of the beautiful
carved and sculptured work of the French cathedrals the new movement
appears in the earlier part of the thirteenth century. At such a place
as Chartres we see the attempt to render plants and animals faithfully
in stone as early as 1240 or before. In the easier medium of parchment
the same tendency appears even earlier. When once it begins the process
progresses slowly until the great recovery of the Greek texts in the
fifteenth century, when it is again accelerated.
During the sixteenth century the energy of botanists and zoologists was
largely absorbed in producing most carefully annotated and illustrated
editions of Dioscorides and Theophrastus and accounts of animals,
habits, and structure that were intended to illustrate the writings of
Aristotle, while the anatomists explored the bodies of man and beast to
confirm or refute Galen. The great monographs on birds, fishes, and
plants of this period, ostensibly little but commentaries on Pliny,
Aristotle, and Dioscorides, represent really the first important efforts
of modern times at a natural history. They pass naturally into the
encyclopaedias of the later sixteenth century, and these into the
physiological works of the seventeenth. Aristotle was never a dead hand
in Biology as he was in Physics, and this for the reason that he was a
great biologist but was not a great physicist.
With the advance of the sixteenth century the works of Aristotle, and to
a less extent those of Dioscorides and Galen, became the great stimulus
to the foundation of a new biological science. Matthioli (1520-77), in
his commentary on Dioscorides (first edition 1544), which was one of the
first works of its type to appear in the vernacular, made a number of
first-hand observations on the habits and structure of plants that is
startling even to a modern botanist. About the same time Galenic
physiology, expressed also in numerous works in the vulgar tongue and
rousing the curiosity of the physicians, became the clear parent of
modern physiology and comparative anatomy. But, above all, the
Aristotelian biological works were fertilizers of the mind. It is very
interesting to watch a fine observer such as Fabricius ab Acquapendente
(1537-1619) laying the foundations of modern embryology in a splendid
series of first-hand observations, treating his own great researches
almost as a commentary on Aristotle. What an impressive contrast to the
arid physics of the time based also on Aristotle! 'My purpose', says
Fabricius, 'is to treat of the formation of the foetus in every animal,
setting out from that which proceeds from the egg: for this ought to
take precedence of all other discussion of the subject, both because it
is not difficult to make out Aristotle's view of the matter, and because
his treatise on the Formation of the Foetus from the egg is by far the
fullest, and the subject is by much the most extensive and
difficult.'[52]
[52] Hieronimo Fabrizio of Acquapendente, _De formato foetu_, Padua,
1604.
The industrious and careful Fabricius, with a wonderful talent for
observation lit not by his own lamp but by that of Aristotle, bears a
relation to the master much like that held by Aristotle's pupil in the
flesh, Theophrastus. The works of the two men, Fabricius and
Theophrastus, bear indeed a resemblance to each other. Both rely on the
same group of general ideas, both progress in much the same ordered calm
from observation to observation, both have an inspiration which is
efficient and stimulating but below the greatest, both are enthusiastic
and effective as investigators of fact, but timid and ineffective in
drawing conclusions.
But Fabricius was more happy in his pupils than Theophrastus, for we may
watch the same Aristotelian ideas fermenting in the mind of Fabricius's
successor, the greatest biologist since Aristotle himself, William
Harvey (1578-1657).[53] This writer's work _On generation_ is a careful
commentary on Aristotle's work on the same topic, but it is a commentary
not in the old sense but in the spirit of Aristotle himself. Each
statement is weighed and tested in the light of experience, and the
younger naturalist, with all his reverence for Aristotle, does not
hesitate to criticize his conclusions. He exhibits an independence of
thought, an ingenuity in experiment, and a power of deduction that
places his treatise as the middle term of the three great works on
embryology of which the other members are those of Aristotle and Karl
Ernst von Baer (1796-1876).[54]
[53] William Harvey, _Exercitationes de generatione animalium_,
London, 1651.
[54] Karl Ernst von Baer, _Ueber die Entwickelungsgeschichte der
Thiere_, Königsberg, 1828-37.
With the second half of the seventeenth century and during a large part
of the eighteenth the biological works of Aristotle attracted less
attention. The battle against the Aristotelian physics had been fought
and won, but with them the biological works of Aristotle unjustly passed
into the shadow that overhung all the idols of the Middle Ages.
The rediscovery of the Aristotelian biology is a modern thing. The
collection of the vast wealth of living forms absorbed the energies of
the generations of naturalists from Ray (1627-1705) and Willoughby
(1635-72) to Réaumur (1683-1757) and Linnaeus (1707-1778) and beyond to
the nineteenth century. The magnitude and fascination of the work seems
almost to have excluded general ideas. With the end of this period and
the advent of a more philosophical type of naturalist, such as Cuvier
(1769-1832) and members of the Saint-Hilaire family, Aristotle came
again to his own. Since the dawn of the nineteenth century, and since
naturalists have been in a position to verify the work of Aristotle, his
reputation as a naturalist has continuously risen. Johannes Müller
(1801-58), Richard Owen (1804-92), George Henry Lewes (1817-78), William
Ogle (1827-1912) are a few of the long line of those who have derived
direct inspiration from his biological work. With improved modern
methods of investigation the problems of generation have absorbed a
large amount of biological attention, and interest has become specially
concentrated on Aristotle's work on that topic which is perhaps, at the
moment, more widely read than any biological treatise, ancient or
modern, except the works of Darwin. That great naturalist wrote to Ogle
in 1882: 'From quotations I had seen I had a high notion of Aristotle's
merits, but I had not the most remote notion what a wonderful man he
was. Linnaeus and Cuvier have been my two gods, though in very different
ways, but they were mere schoolboys to old Aristotle.'