Greek science, however, exhibits throughout its history a peculiar
characteristic differentiating it from the modern scientific standpoint.
Most of the work of the Greek scientist was done in relation to man.
Nature interested him mainly in relation to himself. The Greek
scientific and philosophic world was an anthropocentric world, and this
comes out in the overwhelming mass of medical as distinct from
biological writings that have come down to us. Such, too, is the
sentiment expressed by the poets in their descriptions of the animal
creation:
Many wonders there be, but naught more wondrous than man:
* * * * *
The light-witted birds of the air, the beasts of the weald and the wood
He traps with his woven snare, and the brood of the briny flood.
Master of cunning he: the savage bull, and the hart
Who roams the mountain free, are tamed by his infinite art.
And the shaggy rough-maned steed is broken to bear the bit.
Sophocles, _Antigone_, verses 342 ff.
(Translation of F. Storr.)
It is thus not surprising that our first systematic treatment of animals
is in a practical medical work, the περι διαιτης {peri diaitês}, _On
diet_, of the Hippocratic Collection. This very peculiar treatise dates
from the later part of the fifth century. It is strongly under the
influence of Heracleitus (_c._ 540-475) and contains many points of view
which reappear in later philosophy. All animals, according to it, are
formed of fire and water, nothing is born and nothing dies, but there is
a perpetual and eternal revolution of things, so that change itself is
the only reality. Man's nature is but a parallel to that of the
universal nature, and the arts of man are but an imitation or reflex of
the natural arts or, again, of the bodily functions. The soul, a mixture
of water and fire, consumes itself in infancy and old age, and increases
during adult life. Here, too, we meet with that singular doctrine, not
without bearing on the course of later biological thought, that in the
foetus all parts are formed simultaneously. On the proportion of fire
and water in the body all depends, sex, temper, temperament, intellect.
Such speculative ideas separate this book from the sober method of the
more typical Hippocratic medical works with which indeed it has little
in common.
After having discussed these theoretical matters the work turns to its
own practical concerns, and in the course of setting out the natures of
foods gives in effect a rough classification of animals. These are set
forth in groups, and from among the larger groups only the reptiles and
insects are missing. The list has been described, perhaps hardly with
justification, as the _Coan classificatory system_. We have here,
indeed, no _system_ in the sense in which that word is now applied to
the animal kingdom, but we have yet some sort of definite arrangement of
animals according to their supposed natures. The passage opens with
mammals, which are divided into domesticated and wild, the latter being
mentioned in order according to size, next follow the land-birds, then
the water-fowl, and then the fishes. These fish are divided into (1) the
haunters of the shore, (2) the free-swimming forms, (3) the
cartilaginous fishes or Selachii, which are not so named but are placed
together, (4) the mud-loving forms, and (5) the fresh-water fish.
Finally come invertebrates arranged in some sort of order according to
their structure. The characteristic feature of the 'classification' is
the separation of the fish from the remaining vertebrates and of the
invertebrates from both. Of the fifty animals named no less than twenty
are fish, about a fifth of the number studied by Aristotle, but we must
remember that here only edible species are mentioned. The existence of
the work shows at least that in the fifth century there was already a
close and accurate study of animal forms, a study that may justly be
called scientific. The predominance of fish and their classification in
greater detail than the other groups is not an unexpected feature. The
Mediterranean is especially rich in these forms, the Greeks were a
maritime people, and Greek literature is full of imagery drawn from the
fisher's craft. From Minoan to Byzantine times the variety, beauty, and
colour of fish made a deep impression on Greek minds as reflected in
their art.
Much more important, however, for subsequent biological development
than such observations on the nature and habits of animals, is the
service that the Hippocratic physicians rendered to Anatomy and to
Physiology, departments in which the structure of man and of the
domesticated animals stands apart from that of the rest of the animal
kingdom. It is with the nature and constitution of man that most of the
surviving early biological writings are concerned, and in these
departments are unmistakable tendencies towards systematic arrangement
of the material. Thus we have division and description of the body in
sevens from the periphery to the centre and from the vertex to the sole
of the foot,[9] or a division into four regions or zones.[10] The
teaching concerning the four elements and four humours too became of
great importance and some of it was later adopted by Aristotle. We also
meet numerous mechanical explanations of bodily structures, comparisons
between anatomical conditions encountered in related animals,
experiments on living creatures,[11] systematic incubation of hen's eggs
for the study of their development, parallels drawn between the
development of plants and of human and animal embryos, theories of
generation, among which is that which was afterwards called
'pangenesis'--discussion of the survival of the stronger over the
weaker--almost our survival of the fittest--and a theory of inheritance
of acquired characters.[12] All these things show not only extensive
knowledge but also an attempt to apply such knowledge to human needs.
When we consider how even in later centuries biology was linked with
medicine, and how powerful and fundamental was the influence of the
Hippocratic writings, not only on their immediate successors in
antiquity, but also on the Middle Ages and right into the nineteenth
century, we shall recognize the significance of these developments.
[9] περι ἑβδομαδων {peri hebdomadôn}. The Greek text is lost. We
have, however, an early and barbarous Latin translation, and there
has recently been printed an Arabic commentary. G. Bergstrasser,
_Pseudogaleni in Hippocratis de septimanis commentarium ab Hunnino
Q. F. arabice versum_, Leipzig, 1914.
[10] περι νουσων δ {peri nousôn d}.
[11] περι καρδιης {peri kardiês}.
[12] Especially in the περι γονης {peri gonês}.
[Illustration: Fig. 5. MINOAN GOLD CUP. SIXTEENTH CENTURY B. C.]
[Illustration: Fig. 6. HORSE'S HEAD. FROM PARTHENON. 440 B. C.]
Such was the character of biological thought within the fifth century,
and a generation inspired by this movement produced some noteworthy
works in the period which immediately followed. In the treatise περι
τροφης {peri trophês}, _On nourishment_, which may perhaps be dated
about 400 B. C., we learn of the pulse for the first time in Greek
medical literature, and read of a physiological system which lasted
until the time of Harvey, with the arteries arising from the heart and
the veins from the liver. Of about the same date is a work περι καρδιης
{peri kardiês}, _On the heart_, which describes the ventricles as well
as the great vessels and their valves, and compares the heart of animals
with that of man.
A little later, perhaps 390 B. C., is the treatise περι σαρκων {peri
sarkôn}, _On muscles_, which contains much more than its title suggests.
It has the old system of sevens and, inspired perhaps by the philosophy
of Heracleitus (_c._ 540-475), describes the heart as sending air, fire,
and movement to the different parts of the body through the vessels
which are themselves constantly in movement. The infant in its mother's
womb is believed to draw in air and fire through its mouth and to eat
_in utero_. The action of the air on the blood is compared to its action
on fire. In contrast to some of the other Hippocratic treatises the
central nervous system is in the background; much attention, however, is
given to the special senses. The brain resounds during audition. The
olfactory nerves are hollow, lead to the brain, and, convey volatile
substances to it which cause it to secrete mucus. The eyes also have
been examined, and their coats and humours roughly described; an
allusion, the first in literature, is perhaps made to the crystalline
lens, and the eyes of animals are compared with those of man. There is
evidence not only of dissection but of experiment, and in efforts to
compare the resistance of various tissues to such processes as boiling,
we may see the small beginning of chemical physiology.
An abler work than any of these, but exhibiting less power of
observation is a treatise, περι γονης {peri gonês}, _On generation_,
that may perhaps be dated about 380 B. C.[13] It exhibits a writer of
much philosophic power, very anxious for physiological explanations, but
hampered by ignorance of physics. He has, in fact, the weaknesses and in
a minor degree the strength of his successor Aristotle, of whose great
work on generation he gives us a fore-taste. He sets forth in
considerable detail a doctrine of pangenesis, not wholly unlike that of
Darwin. In order to explain the phenomena of inheritance he supposes
that vessels reach the seed, carrying with them samples from all parts
of the body. He believes that channels pass from all the organs to the
brain and then to the spinal marrow (or to the marrow direct), thence to
the kidneys and on to the genital organs; he believes, too, that he
knows the actual location of one such channel, for he observes, wrongly,
that incision behind the ears, by interrupting the passage, leads to
impotence. As an outcome of this theory he is prepared to accept
inheritance of acquired characters. The embryo develops and breathes by
material transmitted from the mother through the umbilical cord. We
encounter here also a very detailed description of a specimen of
exfoliated _membrana mucosa uteri_ which our author mistakes for an
embryo, but his remarks at least exhibit the most eager curiosity.[14]
[13] The three works περι γονης {peri gonês}, περι φυσιος παιδιου
{peri physios paidiou}, περι νουσων δ {peri nousôn d}, _On
generation_, _on the nature of the embryo_, _on diseases, book IV_,
form really one treatise on generation.
[14] περι φυσιος παιδιου {peri physios paidiou}, _On the nature of
the embryo_, § 13. The same experience is described in the περι
σαρκων {peri sarkôn}, _On the muscles_.
The author of this work on generation is thus a 'biologist' in the
modern sense, and among the passages exhibiting him in this light is his
comparison of the human embryo with the chick. 'The embryo is in a
membrane in the centre of which is the navel through which it draws and
gives its breath, and the membranes arise from the umbilical cord....
The structure of the child you will find from first to last as I have
already described.... If you wish, try this experiment: take twenty or
more eggs and let them be incubated by two or more hens. Then each day
from the second to that of hatching remove an egg, break it, and examine
it. You will find exactly as I say, for the nature of the bird can be
likened to that of man. The membranes [you will see] proceed from the
umbilical cord, and all that I have said on the subject of the infant
you will find in a bird's egg, and one who has made these observations
will be surprised to find an umbilical cord in a bird's egg.'[15]
[15] περι φυσιος παιδιου {peri physios paidiou}, _On the nature of
the embryo_, § 29.
The same interest that he exhibits for the development of man and
animals he shows also for plants.
'A seed laid in the ground fills itself with the juices there
contained, for the soil contains in itself juices of every nature
for the nourishment of plants. Thus filled with juice the seed is
distended and swells, and thereby the power (= faculty ἡ δυναμις
{hê dynamis}) diffused in the seed is compressed by pneuma and
juice, and bursting the seed becomes the first leaves. But a time
comes when these leaves can no longer get nourished from the juices
in the seed. Then the seed and the leaves erupt below, for urged by
the leaves the seed sends down that part of its power which is yet
concentrated within it and so the roots are produced as an
extension of the leaves. When at last the plant is well rooted
below and is drawing its nutriment from the earth, then the whole
grain disappears, being absorbed, save for the husk, which is the
most solid part; and even that, decomposing in the earth,
ultimately becomes invisible. In time some of the leaves put forth
branches. The plant being thus produced by humidity from the seed
is still soft and moist. Growing actively both above and below, it
cannot as yet bear fruit, for it has not the quality of force and
reserve (δυναμις ισχυρη και πιαρα {dynamis ischyrê kai piara}) from
which a seed can be precipitated. But when, with time, the plant
becomes firmer and better rooted, it develops veins as passages
both upwards and downwards, and it draws from the soil not only
water but more abundantly also substances that are denser and
fatter. Warmed, too, by the sun, these act as a ferment to the
extremities and give rise to fruit after its kind. The fruit thus
develops much from little, for every plant draws from the earth a
power more abundant than that with which it started, and the
fermentation takes place not at one place but at many.'[16]
[16] περι φυσιος παιδιου {peri physios paidiou}, _On the nature of
the embryo_, § 22.
Nor does our author hesitate to draw an analogy between the plant and
the mammalian embryo. 'In the same way the infant lives within its
mother's womb and in a state corresponding to the health of the mother
... and you will find a complete similitude between the products of the
soil and the products of the womb.'
The early Greek literature is so scantily provided with illustrations
drawn from botanical study, that it is worth considering the remarkable
comparison of generation of plants from cuttings and from seeds in the
same work.
'As regards plants generated from cuttings ... that part of a
branch where it was cut from a tree is placed in the earth and
there rootlets are sent out. This is how it happens: The part of
the plant within the soil draws up juices, swells, and develops a
pneuma (πνευμα ισχει {pneuma ischei}), but not so the part without.
The pneuma and the juice concentrate the power of the plant below
so that it becomes denser. Then the lower end erupts and gives
forth tender roots. Then the plant, taking from below, draws juices
from the roots and transmits them to the part above the soil which
thus also swells and develops pneuma; thus the power from being
diffused in the plant becomes concentrated and budding, gives forth
leaves.... Cuttings, then, differ from seeds. With a seed the
leaves are borne first, then the roots are sent down; with a
cutting the roots form first and then the leaves.'[17]
[17] Ibid. § 23.
But with these works of the early part of the fourth century the first
stage of Greek biology reaches its finest development. Later
Hippocratic treatises which deal with physiological topics are on a
lower plane, and we must seek some external cause for the failure. Nor
have we far to seek. This period saw the rise of a movement that had the
most profound influence on every department of thought. We see the
advent into the Greek world of a great intellectual movement as a result
of which the department of philosophy that dealt with nature receded
before Ethics. Of that intellectual revolution--perhaps the greatest the
world has seen--Athens was the site and Socrates (470-399) the
protagonist. With the movement itself and its characteristic fruit we
are not concerned. But the great successor and pupil of its founder
gives us in the _Timaeus_ a picture of the depth to which natural
science can be degraded in the effort to give a specific teleological
meaning to all parts of the visible Universe. The book and the picture
which it draws, dark and repulsive to the mind trained in modern
scientific method, enthralled the imagination of a large part of mankind
for wellnigh two thousand years. Organic nature appears in this work of
Plato (427-347) as the degeneration of man whom the Creator has made
most perfect. The school that held this view ultimately decayed as a
result of its failure to advance positive knowledge. As the centuries
went by its views became further and further divorced from phenomena,
and the bizarre developments of later Neoplatonism stand to this day as
a warning against any system which shall neglect the investigation of
nature. But in its decay Platonism dragged science down and destroyed by
neglect nearly all earlier biological material. Mathematics, not being a
phenomenal study, suited better the Neoplatonic mood and continued to
advance, carrying astronomy with it for a while--astronomy that affected
the life of man and that soon became the handmaid of astrology;
medicine, too, that determined the conditions of man's life was also
cherished, though often mistakenly, but pure science was doomed.
But though the ethical view of nature overwhelmed science in the end,
the advent of the mighty figure of Aristotle (384-322) stayed the tide
for a time. Yet the writer on Greek Biology remains at a disadvantage in
contrast with the Historian of Greek Mathematics, of Greek Astronomy, or
of Greek Medicine, in the scantiness of the materials for presenting an
account of the development of his studies before Aristotle. The huge
form of that magnificent naturalist completely overshadows Greek as it
does much of later Biology.