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FATHERS OF BIOLOGY
BY
CHARLES McRAE, M.A., F.L.S.
FORMERLY SCHOLAR OF EXETER COLLEGE, OXFORD
PERCIVAL & CO.
_KING STREET, COVENT GARDEN_
LONDON
1890
Transcriber's Note:
Minor typographical errors have been corrected without note. Archaic
and variant spellings remain as originally printed. Greek text has
been transliterated and is shown between {braces}. The oe ligature
is shown as [oe].
PREFACE.
It is hoped that the account given, in the following pages, of the lives
of five great naturalists may not be found devoid of interest. The work
of each one of them marked a definite advance in the science of Biology.
There is often among students of anatomy and physiology a tendency to
imagine that the facts with which they are now being made familiar have
all been established by recent observation and experiment. But even the
slight knowledge of the history of Biology, which may be obtained from a
perusal of this little book, will show that, so far from such being the
case, this branch of science is of venerable antiquity. And, further, if
in the place of this misconception a desire is aroused in the reader for
a fuller acquaintance with the writings of the early anatomists the
chief aim of the author will have been fulfilled.
CONTENTS.
PAGE
HIPPOCRATES 1
ARISTOTLE 19
GALEN 45
VESALIUS 63
HARVEY 83
HIPPOCRATES.
_HIPPOCRATES._
Owing to the lapse of centuries, very little is known with certainty of
the life of Hippocrates, who was called with affectionate veneration by
his successors "the divine old man," and who has been justly known to
posterity as "the Father of Medicine."
He was probably born about 470 B.C., and, according to all accounts,
appears to have reached the advanced age of ninety years or more. He
must, therefore, have lived during a period of Greek history which was
characterized by great intellectual activity; for he had, as his
contemporaries, Pericles the famous statesman; the poets Æschylus,
Sophocles, Euripides, Aristophanes, and Pindar; the philosopher
Socrates, with his disciples Xenophon and Plato; the historians
Herodotus and Thucydides; and Phidias the unrivalled sculptor.
In the island of Cos, where he was born, stood one of the most
celebrated of the temples of Æsculapius, and in this temple--because he
was descended from the Asclepiadæ--Hippocrates inherited from his
forefathers an important position. Among the Asclepiads the habit of
physical observation, and even manual training in dissection, were
imparted traditionally from father to son from the earliest years, thus
serving as a preparation for medical practice when there were no written
treatises to study.[1]
Although Hippocrates at first studied medicine under his father, he had
afterwards for his teachers Gorgias and Democritus, both of classic
fame, and Herodicus, who is known as the first person who applied
gymnastic exercises to the cure of diseases.
The Asclepions, or temples of health, were erected in various parts of
Greece as receptacles for invalids, who were in the habit of resorting
to them to seek the assistance of the god. These temples were mostly
situated in the neighbourhood of medicinal springs, and each devotee at
his entrance was made to undergo a regular course of bathing and
purification. Probably his diet was also carefully attended to, and at
the same time his imagination was worked upon by music and religious
ceremonies. On his departure, the restored patient usually showed his
gratitude by presenting to the temple votive tablets setting forth the
circumstances of his peculiar case. The value of these to men about to
enter on medical studies can be readily understood; and it was to such
treasures of recorded observations--collected during several
generations--that Hippocrates had access from the commencement of his
career.
Owing to the peculiar constitution of the Asclepions, medical and
priestly pursuits had, before the time of Hippocrates, become combined;
and, consequently, although rational means were to a certain extent
applied to the cure of diseases, the more common practice was to resort
chiefly to superstitious modes of working upon the imagination. It is
not surprising, therefore, to find that every sickness, especially
epidemics and plagues, were attributed to the anger of some offended
god, and that penance and supplications often took the place of personal
and domestic cleanliness, fresh air, and light.
It was Hippocrates who emancipated medicine from the thraldom of
superstition, and in this way wrested the practice of his art from the
monopoly of the priests. In his treatise on "The Sacred Disease"
(possibly epilepsy), he discusses the controverted question whether or
not this disease was an infliction from the gods; and he decidedly
maintains that there is no such a thing as a sacred disease, for all
diseases arise from natural causes, and no one can be ascribed to the
gods more than another. He points out that it is simply because this
disease is unlike other diseases that men have come to regard its cause
as divine, and yet it is not really more wonderful than the paroxysms
of fevers and many other diseases not thought sacred. He exposes the
cunning of the impostors who pretend to cure men by purifications and
spells; "who give themselves out as being excessively religious, and as
knowing more than other people;" and he argues that "whoever is able, by
purifications and conjurings, to drive away such an affection, will be
able, by other practices, to excite it, and, according to this view, its
divine nature is entirely done away with." "Neither, truly," he
continues, "do I count it a worthy opinion to hold that the body of a
man is polluted by the divinity, the most impure by the most holy; for,
were it defiled, or did it suffer from any other thing, it would be like
to be purified and sanctified rather than polluted by the divinity." As
an additional argument against the cause being divine, he adduces the
fact that this disease is hereditary, like other diseases, and that it
attacks persons of a peculiar temperament, namely, the phlegmatic, but
not the bilious; and "yet if it were really more divine than the
others," he justly adds, "it ought to befall all alike."
Again, speaking of a disease common among the Scythians, Hippocrates
remarks that the people attributed it to a god, but that "to me it
appears that such affections are just as much divine as all others are,
and that no one disease is either more divine or more human than
another, but that all are alike divine, for that each has its own
nature, and that no one arises without a natural cause."
From this it will be seen that Hippocrates regarded all phenomena as at
once divine and scientifically determinable. In this respect it is
interesting to compare him with one of his most illustrious
contemporaries, namely, with Socrates, who distributed phenomena into
two classes: one wherein the connection of antecedent and consequent was
invariable and ascertainable by human study, and wherein therefore
future results were accessible to a well-instructed foresight; the
other, which the gods had reserved for themselves and their
unconditional agency, wherein there was no invariable or ascertainable
sequence, and where the result could only be foreknown by some omen or
prophecy, or other special inspired communication from themselves. Each
of these classes was essentially distinct, and required to be looked at
and dealt with in a manner radically incompatible with the other.
Physics and astronomy, in the opinion of Socrates, belonged to the
divine class of phenomena in which human research was insane, fruitless,
and impious.[2]
Hippocrates divided the causes of diseases into two classes: the one
comprehending the influence of seasons, climates, water, situation, and
the like; the other consisting of such causes as the amount and kind of
food and exercise in which each individual indulges. He considered that
while heat and cold, moisture and dryness, succeeded one another
throughout the year, the human body underwent certain analogous changes
which influenced the diseases of the period. With regard to the second
class of causes producing diseases, he attributed many disorders to a
vicious system of diet, for excessive and defective diet he considered
to be equally injurious.
In his medical doctrines Hippocrates starts with the axiom that the body
is composed of the four elements--air, earth, fire, and water. From
these the four fluids or humours (namely, blood, phlegm, yellow bile,
and black bile) are formed. Health is the result of a right condition
and proper proportion of these humours, disease being due to changes in
their quality or distribution. Thus inflammation is regarded as the
passing of blood into parts not previously containing it. In the course
of a disorder proceeding favourably, these humours undergo spontaneous
changes in quality. This process is spoken of as _coction_, and is the
sign of returning health, as preparing the way for the expulsion of the
morbid matters--a state described as the _crisis_. These crises have a
tendency to occur at certain periods, which are hence called _critical
days_. As the critical days answer to the periods of the process of
coction, they are to be watched with anxiety, and the actual condition
of the patient at these times is to be compared with the state which it
was expected he ought to show. From these observations the physician may
predict the course which the remainder of the disease will probably
take, and derive suggestions as to the practice to be followed in order
to assist Nature in her operations.
Hippocrates thus appears to have studied "the natural history of
diseases." As stated above, his practice was to watch the manner in
which the humours were undergoing their fermenting coction, the
phenomena displayed in the critical days, and the aspect and nature of
the critical discharges--not to attempt to check the process going on,
but simply to assist the natural operation. His principles and practice
were based on the theory of the existence of a restoring essence (or
{physis}) penetrating through all creation; the agent which is
constantly striving to preserve all things in their natural state, and
to restore them when they are preternaturally deranged. In the
management of this _vis medicatrix naturæ_ the art of the physician
consisted. Attention, therefore, to regimen and diet was the principal
remedy Hippocrates employed; nevertheless he did not hesitate, when he
considered that occasion required, to administer such a powerful drug as
hellebore in large doses.
The writings which are extant under the name of Hippocrates cannot all
be ascribed to him. Many were doubtless written by his family, his
descendants, or his pupils. Others are productions of the Alexandrian
school, some of these being considered by critics as wilful forgeries,
the high prices paid by the Ptolemies for books of reputation probably
having acted as inducements to such fraud. The following works have
generally been admitted as genuine:--
1. On Airs, Waters, and Places.
2. On Ancient Medicine.
3. On the Prognostics.
4. On the Treatment in Acute Diseases.
5. On Epidemics [Books I. and III.].
6. On Wounds of the Head.
7. On the Articulations.
8. On Fractures.
9. On the Instruments of Reduction.
10. The Aphorisms [Seven Books].
11. The Oath.
The works "On Fractures," "On the Articulations," "On Injuries to the
Head," and "On the Instruments of Reduction," deal with anatomical or
surgical matters, and exhibit a remarkable knowledge of osteology and
anatomy generally. It has sometimes been doubted if Hippocrates could
ever have had opportunities of gaining this knowledge from dissections
of the human body, for it has been thought that the feeling of the age
was diametrically opposed to such a practice, and that Hippocrates would
not have dared to violate this feeling. The language used, however, in
some passages in the work "On the Articulations," seems to put the
matter beyond doubt. Thus he says in one place, "But if one will strip
the point of the shoulder of the fleshy parts, and where the muscle
extends, and also lay bare the tendon that goes from the armpit and
clavicle to the breast," etc. And again, further on in the same
treatise, "It is evident, then, that such a case could not be reduced
either by succussion or by any other method, unless one were to cut open
the patient, and then, having introduced the hand into one of the great
cavities, were to push outwards from within, which one might do in the
dead body, but not at all in the living."
His descriptions of the vertebræ, with all their processes and
ligaments, as well as his account of the general characters of the
internal viscera, would not have been as free from error as they are if
he had derived all his knowledge from the dissection of the inferior
animals. Moreover, it is indisputable that, within less than a hundred
years from the death of Hippocrates, the human body was openly dissected
in the schools of Alexandria--nay, further, that even the vivisection of
condemned criminals was not uncommon. It would be unreasonable to
suppose that such a practice as the former sprang up suddenly under the
Ptolemies, and it seems, therefore, highly probable that it was known
and tolerated in the time of Hippocrates. It is not surprising, when we
remember the rude appliances and methods which then obtained, that in
his knowledge of minute anatomy Hippocrates should compare unfavourably
with anatomists of the present day. Of histology, and such other
subjects as could not be brought within his direct personal observation,
the knowledge of Hippocrates was necessarily defective. Thus he wrote of
the tissues without distinguishing them; confusing arteries, veins, and
nerves, and speaking of muscles vaguely as "flesh." But with matters
within the reach of the Ancient Physician's own careful observation, the
case is very different. This is well shown in his wonderful chapter on
the club-foot, in which he not only states correctly the true nature of
the malformation, but gives some very sensible directions for rectifying
the deformity in early life.
When human strength was not sufficient to restore a displaced limb, he
skilfully availed himself of all the mechanical powers which were then
known. He does not appear to have been acquainted with the use of
pulleys for the purpose, but the axles which he describes as being
attached to the bench which bears his name (_Scamnum Hippocratis_) must
have been quite capable of exercising the force required.
The work called "The Aphorisms," which was probably written in the old
age of Hippocrates, consists of more than four hundred short pithy
sentences, setting forth the principles of medicine, physiology, and
natural philosophy. A large number of these sentences are evidently
taken from the author's other works, especially those "On Air," etc.,
"On Prognostics," and "On the Articulations." They embody the result of
a vast amount of observation and reflection, and the majority of them
have been confirmed by the experience of two thousand years. A proof of
the high esteem in which they have always been held is furnished by the
fact that they have been translated into all the languages of the
civilized world; among others, into Hebrew, Arabic, Latin, English,
Dutch, Italian, German, and French. The following are a few examples of
these aphorisms:--
"Spontaneous lassitude indicates disease."
"Old people on the whole have fewer complaints than the young; but
those chronic diseases which do befall them generally never leave
them."
"Persons who have sudden and violent attacks of fainting without any
obvious cause die suddenly."
"Of the constitutions of the year, the dry upon the whole are more
healthy than the rainy, and attended with less mortality."
"Phthisis most commonly occurs between the ages of eighteen and
thirty-five years."
"If one give to a person in fever the same food which is given to a
person in good health, what is strength to the one is disease to the
other."
"Such food as is most grateful, though not so wholesome, is to be
preferred to that which is better, but distasteful."
"Life is short and the art long; the opportunity fleeting;
experience fallacious and judgment difficult. The physician must not
only do his duty himself, but must also make the patient, the
attendants and the externals, co-operate."
Hippocrates appears to have travelled a great deal, and to have
practised his art in many places far distant from his native island. A
few traditions of what he did during his long life remain, but
differences of opinion exist as to the truth of these stories.
Thus one story says that when Perdiccas, the King of Macedonia, was
supposed to be dying of consumption, Hippocrates discovered the disorder
to be love-sickness, and speedily effected a cure. The details of this
story scarcely seem to be worthy of credence, more especially as similar
legends have been told of entirely different persons belonging to widely
different times. There are, however, some reasons for believing that
Hippocrates visited the Macedonian court in the exercise of his
professional duties, for he mentions in the course of his writings,
among places which he had visited, several which were situated in
Macedonia; and, further, his son Thessalus appears to have afterwards
been court physician to Archelaus, King of Macedonia.
Another story connects the name of Hippocrates with the Great Plague
which occurred at Athens in the time of the Peloponnesian war. It is
said that Hippocrates advised the lighting of great fires with wood of
some aromatic kind, probably some species of pine. These, being kindled
all about the city, stayed the progress of the pestilence. Others
besides Hippocrates are, however, famous for having successfully adopted
this practice.
A third legend states that the King of Persia, pursuing the plan (which
in the two celebrated instances of Themistocles and Pausanias had proved
successful) of attracting to his side the most distinguished persons in
Greece, wrote to Hippocrates asking him to pay a visit to his court, and
that Hippocrates refused to go. Although the story is discarded by many
scholars, it is worthy of note that Ctesias, a kinsman and contemporary
of Hippocrates, is mentioned by Xenophon in the "Anabasis" as being in
the service of the King of Persia. And, with regard to the refusal of
the venerable physician to comply with the king's request, one cannot
lose sight of the fact that such refusal was the only course consistent
with the opinions he professed of a monarchical form of government.
After his various travels Hippocrates, as seems to be pretty generally
admitted, spent the latter portion of his life in Thessaly, and died at
Larissa at a very advanced age.
It is difficult to speak of the skill and painstaking perseverance of
Hippocrates in terms which shall not appear exaggerated and
extravagant. His method of cultivating medicine was in the true spirit
of the inductive philosophy. His descriptions were all derived from
careful observation of its phenomena, and, as a result, the greater
number of his deductions have stood unscathed the test of twenty
centuries.
Still more difficult is it to speak with moderation of the candour which
impelled Hippocrates to confess errors into which in his earlier
practice he had fallen; or of that freedom from superstition which
entitled him to be spoken of as a man who knew not how to deceive or be
deceived ("qui tam fallere quam falli nescit"); or, lastly, of that
purity of character and true nobility of soul which are brought so
distinctly to light in the words of the oath translated below:--
"I swear by Apollo the Physician and Æsculapius, and I call Hygeia
and Panacea and all the gods and goddesses to witness, that to the
best of my power and judgment I will keep this oath and this
contract; to wit--to hold him, who taught me this Art, equally dear
to me as my parents; to share my substance with him; to supply him
if he is in need of the necessaries of life; to regard his offspring
in the same light as my own brothers, and to teach them this Art, if
they shall desire to learn it, without fee or contract; to impart
the precepts, the oral teaching, and all the rest of the instruction
to my own sons, and to the sons of my teacher, and to pupils who
have been bound to me by contract, and who have been sworn according
to the law of medicine.
"I will adopt that system of regimen which, according to my ability
and judgment, I consider for the benefit of my patients, and will
protect them from everything noxious and injurious. I will give no
deadly medicine to any one, even if asked, nor will I give any such
counsel, and similarly I will not give to a woman the means of
procuring an abortion. With purity and with holiness I will pass my
life and practise my art.... Into whatever houses I enter I will go
into them for the benefit of the sick, keeping myself aloof from
every voluntary act of injustice and corruption and lust. Whatever
in the course of my professional practice, or outside of it, I see
or hear which ought not to be spread abroad, I will not divulge, as
reckoning that all such should be kept secret. If I continue to
observe this oath and to keep it inviolate, may it be mine to enjoy
life and the practice of the Art respected among all men for ever.
But should I violate this oath and forswear myself, may the reverse
be my lot."
FOOTNOTES:
[1] Grote's "Aristotle," vol. i. p. 3.
[2] Grote's "History of Greece," vol. i. p. 358.
ARISTOTLE.
_ARISTOTLE._
About the time that Hippocrates died, Aristotle, who may be regarded as
the founder of the science of "Natural History," was born (B.C. 384) in
Stagira, an unimportant Hellenic colony in Thrace, near the Macedonian
frontier. His father was a distinguished physician, and, like
Hippocrates, boasted descent from the Asclepiadæ. The importance
attached by the Asclepiads to the habit of physical observation, which
has been already referred to in the life of Hippocrates, secured for
Aristotle, from his earliest years, that familiarity with biological
studies which is so clearly evident in many of his works.
Both parents of Aristotle died when their son was still a youth, and in
consequence of this he went to reside with Proxenus, a native of
Atarneus, who had settled at Stagira. Subsequently he went to Athens and
joined the school of Plato. Here he remained for about twenty years, and
applied himself to study with such energy that he became pre-eminent
even in that distinguished band of philosophers. He is said to have
been spoken of by Plato as "the intellect" of the school, and to have
been compared by him to a spirited colt that required the application of
the rein to restrain its ardour.
Aristotle probably wrote at this time some philosophical works, the fame
of which reached the ears of Philip, King of Macedonia, and added to the
reputation which the young philosopher had already made with that
monarch; for Philip is said to have written to him on the occasion of
Alexander's birth, B.C. 356: "King Philip of Macedonia to Aristotle,
greeting. Know that a son has been born to me. I thank the gods not so
much that they have given him to me, as that they have permitted him to
be born in the time of Aristotle. I hope that thou wilt form him to be a
king worthy to succeed me and to rule the Macedonians."
After the death of Plato, which occurred in 347 B.C., Aristotle quitted
Athens and went to Atarneus, where he stayed with Hermias, who was then
despot of that town. Hermias was a remarkable man, who, from being a
slave, had contrived to raise himself to the supreme power. He had been
at Athens and had heard Plato's lectures, and had there formed a
friendship for Aristotle. With this man the philosopher remained for
three years, and was then compelled suddenly to seek refuge in Mitylene,
owing to the perfidious murder of Hermias. The latter was decoyed out of
the town by the Persian general, seized and sent prisoner to
Artaxerxes, by whom he was hanged as a rebel. On leaving Atarneus,
Aristotle took with him a niece of Hermias, named Pythias, whom he
afterwards married. She died young, leaving an infant daughter.
Two or three years after this, Aristotle became tutor to Alexander, who
was then about thirteen years old. The philosopher seems to have been a
favourite with both the king and the prince, and, in gratitude for his
services, Philip rebuilt Stagira and restored it to its former
inhabitants, who had either been dispersed or carried into slavery. The
king is said also to have established there a school for Aristotle. The
high respect in which Alexander held his teacher is expressed in his
saying that he honoured him no less than his own father, for while to
one he owed life, to the other he owed all that made life valuable.
In 336 B.C. Alexander, who was then only about twenty years of age,
became king, and Aristotle soon afterwards quitted Macedonia and took up
his residence in Athens once more, after an absence of about twelve
years. Here he opened a school in the Lycæum, a gymnasium on the eastern
side of the city, and continued his work there for about twelve years,
during which time Alexander was making his brilliant conquests. The
lectures were given for the most part while walking in the garden, and
in consequence, perhaps, of this, the sect received the name of the
Peripatetics. The discourses were of two kinds--the _esoteric_, or
abstruse, and the _exoteric_, or familiar; the former being delivered to
the more advanced pupils only. During the greater part of this time
Aristotle kept up correspondence with Alexander, who is said[3] to have
placed at his disposal thousands of men, who were busily employed in
collecting objects and in making observations for the completion of the
philosopher's zoological researches. Alexander is, moreover, said to
have given the philosopher eight hundred talents for the same purpose.
In spite of these marks of friendship and respect, Alexander, who was
fast becoming intoxicated with success, and corrupted by Asiatic
influences, gradually cooled in his attachment towards Aristotle. This
may have been hastened by several causes, and among others by the
freedom of speech and republican opinions of Callisthenes, a kinsman and
disciple of Aristotle, who had been, by the latter's influence,
appointed to attend on Alexander. Callisthenes proved so unpopular, that
the king seems to have availed himself readily of the first plausible
pretext for putting him to death, and to have threatened his former
friend and teacher with a similar punishment. The latter, for his part,
probably had a deep feeling of resentment towards the destroyer of his
kinsman.
Meanwhile the Athenians knew nothing of these altered relations between
Aristotle and Alexander, but continued to regard the philosopher as
thoroughly imbued with kingly notions (in spite of his writings being
quite to the contrary); so that he was an object of suspicion and
dislike to the Athenian patriots. Nevertheless, as long as Alexander was
alive, Aristotle was safe from molestation. As soon, however, as
Alexander's death became known, the anti-Macedonian feeling of the
Athenians burst forth, and found a victim in the philosopher. A charge
of impiety was brought against him. It was alleged that he had paid
divine honours to his wife Pythias and to his friend Hermias. Now, for
the latter, a eunuch, who from the rank of a slave had raised himself to
the position of despot over a free Grecian community, so far from
coupling his name (as Aristotle had done in his hymn) with the greatest
personages of Hellenic mythology, the Athenian public felt that no
contempt was too bitter. To escape the storm the philosopher retired to
Chalcis, in Eub[oe]a, then under garrison by Antipater, the Governor of
Macedonia, remarking in a letter, written afterwards, that he did so in
order that the Athenians might not have the opportunity of sinning a
second time against philosophy (the allusion being, of course, to the
fate of Socrates).
He probably intended to return to Athens again so soon as the political
troubles had abated, but in September, 322 B.C., he died at Chalcis. An
overwrought mind, coupled with indigestion and weakness of the stomach,
from which he had long suffered, was most probably the cause of death.
Some of his detractors, however, have asserted that he took poison, and
others that he drowned himself in the Eub[oe]an Euripus.
It is not easy to arrive at a just estimate of the character of
Aristotle. By some of his successors he has been reproached with
ingratitude to his teacher, Plato; with servility to Macedonian power,
and with love of costly display. How far these two last charges are due
to personal slander it is impossible to say. The only ground for the
first charge is, that he criticised adversely some of Plato's doctrines.
The manuscripts of Aristotle's works passed through many vicissitudes.
At the death of the philosopher they were bequeathed to Theophrastus,
who continued chief of the Peripatetic school for thirty-five years.
Theophrastus left them, with his own works, to a philosophical friend
and pupil, Neleus, who conveyed them from Athens to his residence at
Scepsis, in Asia Minor. About thirty or forty years after the death of
Theophrastus, the kings of Pergamus, to whom the city of Scepsis
belonged, began collecting books to form a library on the Alexandrian
plan. This led the heirs of Neleus to conceal their literary treasures
in a cellar, and there the manuscripts remained for nearly a century
and a half, exposed to injury from damp and worms. At length they were
sold to Apellicon, a resident at Athens, who was attached to the
Peripatetic sect. Many of the manuscripts were imperfect, having become
worm-eaten or illegible. These defects Apellicon attempted to remedy;
but, being a lover of books rather than a philosopher, he performed the
work somewhat unskilfully. When Athens was taken by Sylla, 86 B.C., the
library of Apellicon was transported to Rome. There various literary
Greeks obtained access to it; and, among others, Tyrannion, a grammarian
and friend of Cicero, did good service in the work of correction.
Andronicus of Rhodes afterwards arranged the whole into sections, and
published the manuscripts with a tabulated list.
The three principal works on biology which are extant are: "The History
of Animals;" "On the Parts of Animals;" "On the Generation of Animals."
The other biological works are: "On the Motion of Animals;" "On
Respiration;" "Parva Naturalia;"--a series of essays which are planned
to form an entire work on sense and the sensible.
"The History of Animals" is the largest and most important of
Aristotle's works on biology. It contains a vast amount of information,
not very methodically arranged, and spoiled by the occurrence here and
there of very gross errors. It consists of nine books.
The first book opens with a division of the body into similar and
dissimilar parts. Besides thus differing in their parts, animals also
differ in their mode of life, their actions and dispositions. Thus some
are aquatic, others terrestrial; of the former, some breathe water,
others air, and some neither. Of aquatic animals, some inhabit the sea,
and others rivers, lakes, or marshes. Again, some animals are
locomotive, and others are stationary. Some follow a leader, others act
independently. Various differences are in this way pointed out, and
there is no lack of illustration and detail, but a suspicion is excited
that the generalizations are sometimes based upon insufficient facts.
The book closes with a description of the different parts of the human
body, both internal and external. In speaking of the ear, Aristotle
seems to have been aware of what we now call the Eustachian tube, for he
says, "There is no passage from the ear into the brain, but there is to
the roof of the mouth."[4]
In the second book he passes on to describe the organs of animals. The
animals are dealt with in groups--viviparous and oviparous quadrupeds,
fish, serpents, birds, etc. The ape, elephant, chameleon, and some
others are especially noticed.
The third book continues the description of the internal organs.
References which are made to a diagram by letters, _a_, _b_, _c_, _d_,
show that the work was originally illustrated. At the close of this
book Aristotle has some remarks on milk, and mentions the occasional
appearance of milk in male animals. He speaks of a male goat at Lemnos
which yielded so much that cakes of cheese were made from it. Similar
instances of this phenomenon have been recorded by Humboldt, Burdach,
Geoffroy St. Hilaire, and others.
In the first four chapters of the fourth book the anatomy of the
invertebrata is dealt with, and the accounts given of certain mollusca
and crustacea are very careful and minute. The rest of the book is
devoted to a description of the organs of sense and voice; of sleep, and
the distinctions of sex. The accurate knowledge which Aristotle exhibits
of the anatomy and habits of marine animals, such as the Cephalopoda and
the larger Crustacea, leaves no doubt that he derived it from actual
observation. Professor Owen says, "Respecting the living habits of the
Cephalopoda, Aristotle is more rich in detail than any other zoological
author." What is now spoken of as the _hectocotylization_ of one or more
of the arms of the male cephalopod did not escape Aristotle's eye. And
while he speaks of the teeth and that which serves these animals for a
tongue, it is plain from the context that he means in the one case the
two halves of the parrot-like beak, and in the other the anterior end of
the odontophore.
Books five to seven deal with the subject of generation.
The eighth book contains a variety of details respecting animals, their
food, migrations, hibernation, and diseases; with the influence of
climate and locality upon them.
The ninth book describes the habits and instincts of animals. The
details are interesting; but there is, as usual, very little attempt at
classification. Disjointed statements and sudden digressions occur, the
subjects being treated in the order in which they presented themselves
to the author. Such curious statements as the following are met with:
"The raven is an enemy to the bull and the ass, for it flies round them
and strikes their eyes." "If a person takes a goat by the beard, all the
rest of the herd stand by, as if infatuated, and look at it." "Female
stags are captured by the sound of the pipe and by singing. When two
persons go out to capture them, one shows himself, and either plays upon
a pipe or sings, and the other strikes behind, when the first gives him
the signal." "Swans have the power of song, especially when near the end
of their life; for they then fly out to sea, and some persons sailing
near the coast of Libya have met many of them in the sea singing a
mournful song, and have afterwards seen some of them die." "Of all wild
animals, the elephant is the most tame and gentle; for many of them are
capable of instruction and intelligence, and they have been taught _to
worship the king_."
In the work "On the Parts of Animals," the author considers not only the
phenomena of life exhibited by each species, but also the cause or
causes to which these phenomena are attributable. After a general
introduction, he proceeds to enumerate the three degrees of composition,
viz.:--
(1) "Composition out of what some call the elements, such as air,
earth, water, and fire," or "out of the elementary forces, hot
and cold, solid and fluid, which form the material of all
compound substances."
(2) Composition out of these primary substances of the homogeneous
parts of animals, e.g. blood, fat, marrow, brain, flesh, and
bone.
(3) Composition into the heterogeneous parts or organs. These parts he
describes in detail, considering those belonging to sanguineous
animals first and most fully.
These divisions correspond roughly to the threefold study of structure
which we nowadays recognize as chemical, histological, and anatomical.
As examples of Aristotle's method of treatment, his descriptions of
blood, the brain, the heart, and the lung may be considered.
Of the _blood_ he says, "What are called fibres are found in the blood
of some animals, but not of all. There are none, for instance, in the
blood of deer and of roes, and for this reason the blood of such
animals as these never coagulates.... Too great an excess of water makes
animals timorous.... Such animals, on the other hand, as have thick and
abundant fibres in their blood are of a more choleric temperament, and
liable to bursts of passion.... Bulls and boars are choleric, for their
blood is exceedingly rich in fibres, and the bull's, at any rate,
coagulates more rapidly than that of any other animal.... If these
fibres are taken out of the blood, the fluid that remains will no longer
coagulate."
From these quotations it will be noted that Aristotle attributed the
coagulum to the presence of fibres, and in this he anticipated
Malpighi's discovery made in the seventeenth century. His remarks on the
proportion of coagulum and serum in different animals, which is enlarged
upon in the "History of Animals,"[5] harmonize with modern observations.
In another of his works[6] he remarks that the blood in certain diseased
conditions will not coagulate. This is known to be the case in cholera,
certain fevers, asphyxia, etc.; and the fact was probably obtained from
Hippocrates. Although Aristotle speaks here of entire absence of
coagulation in the blood of the deer and the roe, in the "History of
Animals" he admits an imperfect coagulation, for he says, "so that their
blood does not coagulate like that of other animals." The animals named
are commonly hunted, and it was probably after they had been hunted to
death that he examined them. Now, it is generally admitted that
coagulation under such circumstances is imperfect and even uncommon. The
statement as to the richness in fibres of the blood of bulls and boars
has been confirmed by some modern investigations, which have shown that
the clot bears a proportion to the strength and ferocity of the animal.
The remarks, however, as to the relative rapidity of coagulation would
appear to be contradicted by later observations, for Thackrah came to
the conclusion that coagulation commenced sooner in small and weak
animals than in strong.
Of the _brain_ Aristotle makes the following among other assertions: "Of
all parts of the body there is none so cold as the brain.... Of all the
fluids of the body it is the one that has the least blood, for, in fact,
it has no blood at all in its proper substance.... That it has no
continuity with the organs of sense is plain from simple inspection, and
still more closely shown by the fact that when it is touched no
sensation is produced.... The brain tempers the heat and seething of the
heart.... In order that it may not itself be absolutely without heat,
blood-vessels from the aorta end in the membrane which surrounds the
brain.... Of all animals man has the largest brain in proportion to his
size: and it is larger in men than in women. This is because the region
of the heart and of the lung is hotter and richer in blood in man than
in any other animal; and in men than in women. This again explains why
man alone of animals stands erect. For the heat, overcoming any opposite
inclination, makes growth take its own line of direction, which is from
the centre of the body upwards.... Man again has more sutures in his
skull than any other animal, and the male more than the female. The
explanation is to be found in the greater size of the brain, which
demands free ventilation proportionate to its bulk.... There is no brain
in the hinder part of the head.... The brain in all animals that have
one is placed in the front part of the head ... because the heart, from
which sensation proceeds, is in the front part of the body."
Although it would perhaps be difficult to find anywhere as many errors
in as few words, yet it should be observed that Aristotle here shows
himself to have been aware of the existence of the membranes of the
brain--the _pia mater_ and the _dura mater_; and elsewhere[7] he says
more explicitly, "Two membranes enclose the brain; that about the skull
is the stronger; the inner membrane is slighter than the outer one." And
further, it should be noted that he describes the latter membrane as a
vascular one. The fact of the brain substance being insensible to
mechanical irritation was known to Aristotle, and may have been learnt
from the practice of Hippocrates. Lastly, it should be remembered
that--though this may have been but a lucky guess on Aristotle's
part--the relative weight of brain to the entire body has been shown,
with few exceptions, to be greater in man than in any other animal.
In describing the _heart_ Aristotle says: "The heart lies about the
centre of the body, but rather in its upper than in its lower half, and
also more in front than behind.... In man it inclines a little towards
the left, so that it may counterbalance the chilliness of that side. It
is hollow, to serve for the reception of the blood; while its wall is
thick, that it may serve to protect the source of heat. For here, and
here alone, in all the viscera, and in fact in all the body, there is
blood without blood-vessels, the blood elsewhere being always contained
within vessels. The heart is the first of all the parts of the body to
be formed, and no sooner is it formed than it contains blood.... For no
sooner is the embryo formed than its heart is seen in motion like a
living creature, and this before any of the other parts. The heart is
abundantly supplied with sinews.... In no animal does the heart contain
a bone, certainly in none of those that we ourselves have inspected,
with the exception of the horse and a certain kind of ox. In animals of
great size the heart has three cavities; in smaller animals it has two;
and in all it has at least one."
It will be observed that here Aristotle so correctly describes the
position of the human heart as to render it probable that he is speaking
from actual inspection; although man is not the only animal in which the
heart is turned towards the left. In contrasting the heart with the
other viscera he appears to have overlooked the existence of the
coronary vessels, and to have imagined that the nutrition of the heart
was effected directly by the blood in its cavities. Although the heart
is not really the first part to appear, the observation of its very
early appearance in the embryo, which he treats more fully elsewhere,[8]
is alone enough to establish his reputation as an original observer. It
is remarkable that Aristotle should have overlooked the presence of the
valves of the heart, the structure and functions of which were fully
investigated within thirty years of his death by the anatomists of the
Alexandrian school. This is the more remarkable, as he calls attention
here, and in the "History of Animals," to the sinews or tendons
({neura}) with which, he says, the heart is supplied, and by which he
probably meant chiefly the _chordæ tendineæ_. The "bone in the heart" of
which he speaks was probably the cruciform ossification which is
normally found in the ox and the stag below the origin of the aorta. It
is found in the horse only in advanced age, or under abnormal
conditions. The statement that the heart contains no more than three
chambers has always been considered as a very gross blunder on the part
of Aristotle. Even Cuvier, who generally lavishes upon the philosopher
the most extravagant praise, sneers at this. Professor Huxley,[9]
however, has shown, by a comparison of several passages from the
"History of Animals," that what we now call the right auricle was
regarded by the author as a venous sinus, as being a part not of the
heart, but of the great vein (_i.e._ the superior and the inferior _venæ
cavæ_).
Aristotle speaks of the _lung_ as a single organ, sub-divided, but
having a common outlet--the trachea. Elsewhere[10] he says, "Canals from
the heart pass to the lung and divide in the same fashion as the
windpipe does, closely accompanying those from the windpipe through the
whole lung." His theory of respiration, as explained in his treatise on
the subject, is that it tempers the excessive heat produced in the
heart. The lung is compared to a pair of bellows. When the lung is
expanded, air rushes in; when it is contracted, the air is expelled. The
heat from the heart causes the lung to expand--cold air rushes in, the
heat is reduced, the lung collapses, and the air is expelled. The cold
air drawn into the lung reaches the bronchial tubes, and as the vessels
containing hot blood run alongside these tubes, the air cools it and
carries off its superfluous heat. Some of the air which enters the lung
gets from the bronchial tubes into the blood-vessels by transudation,
for there is no direct communication between them; and this air,
penetrating the body, rapidly cools the blood throughout the vessels.
But Aristotle did not consider the "pneuma," which thus reached the
interior of the blood-vessels, to be exactly the same thing as air--it
was "a subtilized and condensed air."[11] And this we now know to be
oxygen.
The treatise "On the Generation of Animals" is an extraordinary
production. "No ancient and few modern works equal it in
comprehensiveness of detail and profound speculative insight. We here
find some of the obscurest problems of biology treated with a mastery
which, when we consider the condition of science at that day, is truly
astounding. That there are many errors, many deficiencies, and not a
little carelessness in the admission of facts, may be readily imagined;
nevertheless at times the work is frequently on a level with, and
occasionally even rises above, the speculations of many advanced
embryologists."[12]
It commences with the statement that the present work is a sequel to
that "On the Parts of Animals;" and first the masculine and feminine
_principles_ are defined. The masculine principle is the origin of all
motion and generation; the feminine principle is the origin of the
material generated. Aristotle's philosophy of nature was teleological,
and the imperfect character of his anatomical knowledge often gives him
occasion to explain particular phenomena by final causes. Thus animals
producing soft-shelled eggs (_e.g._ cartilaginous fish and vipers) are
said to do so because they have so little warmth that the external
surface of the egg cannot be dried.