Classical and medieval

The birth of biology: 5th - 4th century BC

The Greek philosophers, voracious in their curiosity, look with interest at the range of living creatures, from the humblest plant to man himself. A Greek name is coined by a German naturalist in the early 19th century for this study of all physical aspects of natural life - biology, from bios (life) and logos (word or discourse). It is a subject with clear subdivisions, such as botany, zoology or anatomy. But all are concerned with living organisms.

The first man to make a significant contribution in biology is Alcmaeon, living in Crotona in the 5th century. Crotona is famous at the time for its Pythagorean scholars, but Alcmaeon seems not to have been of their school.

Alcmaeon is the first scientist known to have practised dissection in his researches. His aim is not anatomical, for his interest lies in trying to find the whereabouts of human intelligence. But in the course of his researches he makes the first scientific discoveries in the field of anatomy.

The subsequent Greek theory, subscribed to even by Aristotle, is that the heart is the seat of intelligence. Alcmaeon reasons that since a blow to the head can affect the mind, in concussion, this must be where reason lies. In dissecting corpses to pursue this idea, he observes passages linking the brain with the eyes (the optic nerves) and the back of the mouth with the ears (Eustachian tubes).

Aristotle may be wrong about the brain being in the heart, but in general he gives a far more complete and well observed account of biology than any other Greek philosopher.

He inaugurates scientific zoology in his reliance on careful observation. He is particularly acute in his study of marine life, having much to say on the habits of fishes, the development of the octopus family, and the nature of whales, dolphins and porpoises. He is also a pioneer in attempting a system of Aristotle. Observing an unbroken chain of gradual developments, as the life of plants shades into that of animals, he acknowledges the complexity of the subject and seems almost to glimpse the pattern of evolution.

Aristotle's notes on botany are lost, but many of his observations no doubt survive in the earliest known botanical text - nine books On the History of Plants written by Aristotle's favourite pupil, Theophrastus.

Writing in about 300 BC, Theophrastus attempts to classify plants, as well as describing their structure, habits and uses. His remarks are based on observations carried out in Greece, but he also includes information brought back from the new Classification empire in the Middle East, Persia and India, resulting from the conquests of Alexander the Great.

Human vivisection: c.300 BC

Early in the 3rd century BC two surgeons in Alexandria, Herophilus and Erasistratus, make the first scientific studies designed to discover the workings of human anatomy.

The cost of their contribution to science would be considered too high in modern times (they acquire much of their information from human vivisection, the patients being convicted criminals). But Celsus, a Roman writer on medical history, energetically justifies the suffering of the criminals as providing 'remedies for innocent people of all future ages'.

The influential errors of Galen: 2nd century AD

The newly appointed chief physician to the gladiators in Pergamum, in AD 158, is a native of the city. He is a Greek doctor by the name of Galen. The appointment gives him the opportunity to study wounds of all kinds. His knowledge of muscles enables him to warn his patients of the likely outcome of certain operations - a wise precaution recommended in Galen's advice to doctors.

But it is Galen's dissection of apes and pigs which give him the detailed information for his medical tracts on the organs of the body. Nearly 100 of these tracts survive. They become the basis of Galen's great reputation in medieval medicine, unchallenged until the anatomical work of Vesalius.

Through his experiments Galen is able to overturn many long-held beliefs, such as the theory (first proposed by the Hippocratic school in about 400 BC, and maintained even by the physicians of Alexandria) that the arteries contain air - carrying it to all parts of the body from the heart and the lungs. This belief is based originally on the arteries of dead animals, which appear to be empty.

Galen is able to demonstrate that living arteries contain blood. His error, which will become the established medical orthodoxy for centuries, is to assume that the blood goes back and forth from the heart in an ebb-and-flow motion. This theory holds sway in medical circles until the time of Harvey.

Science's siesta: 8th - 15th century AD

In the profoundly Christian centuries of the European Middle Ages the prevailing mood is not conducive to scientific enquiry. God knows best, and so He should - since He created everything. Where practical knowledge is required, there are ancient authorities whose conclusions are accepted without question - Ptolemy in the field of astronomy, Galen on matters anatomical.

A few untypical scholars show an interest in scientific research. The 13th-century Franciscan friar Roger Bacon is the most often quoted example, but his studies include alchemy and astrology as well as optics and astronomy. The practical scepticism required for science must await the Renaissance.


Leonardw's anatomical drawings: AD 1489-1515

In about 1489 Leonardo da Vinci begins a series of anatomical drawings. For accuracy of observation they are far in advance of anything previously attempted. Over the next twenty-five years he dissects about thirty human corpses, many of them at a mortuary in Rome - until in 1515 the pope, Leo X, orders him to stop.

His drawings, amounting to some 750, include studies of bone structures, muscles, internal organs, the brain and even the position of the foetus in the womb. His studies of the heart suggest that he was on the verge of discovering the concept of the Circulation of the blood.

Vesalius and the science of anatomy: AD 1533-1543

A young medical student, born in Brussels and known to history as Vesalius, attends anatomy lectures in the university of Paris. The lecturer explains human anatomy, as revealed by Galen more than 1000 years earlier, while an assistant points to the equivalent details in a dissected corpse. Often the assistant cannot find the organ as described, but invariably the corpse rather than Galen is held to be in error.

Vesalius decides that he will dissect corpses himself and trust to the evidence of what he finds. His approach is highly controversial. But his evident skill leads to his appointment in 1537 as professor of surgery and anatomy at the university of Padua.

In 1540 Vesalius gives a public demonstration of the inaccuracies of Galen's anatomical theories, which are still the orthodoxy of the medical profession.

Galen did many of his experiments on apes. Vesalius now has on display - for comparison - the skeletons of a human being and of an ape.

Vesalius is able to show that in many cases Galen's observations are indeed correct for the ape, but bear little relation to the man. Clearly what is needed is a new account of human anatomy.

Vesalius sets himself the task of providing it, illustrated in a series of dissections and drawings. He has at his disposal a method, relatively new in Europe, of ensuring accurate distribution of an image in printed form - the art of the Galen. His studies inaugurate the modern science of anatomy.

At Basel, in Switzerland, Vesalius publishes in 1543 his great work - De humani corporis fabrica (The Structure of the Human Body). There are seven volumes including numerous magnificent Galen illustrations. The book is an immediate success, though naturally it enrages the traditionalists who follow Galen. Galen's theories have, after all, the clear merit of seniority. They are by now some 1400 years old.

But for those willing to look with clear eyes, the plates in Vesalius's volumes are a revelation. For the first time human beings can peer beneath their own skins, in these strikingly clear images of what lies hidden.

Harvey and the circulation of the blood: AD 1628

A book is published in 1628 which provides one of the greatest breakthroughs in the understanding of the human body - indeed perhaps the greatest until the discovery of the structure of DNA in the 20th century.

The book consists of just fifty-two tightly argued pages. Its text is in Latin. Its title is Exercitatio anatomica de motu cordis et sanguinis in animalibus ('The Anatomical Function of the Movement of the Heart and the Blood in Animals'). Its author is William Harvey. In this book he demonstrates beyond any reasonable doubt an entirely new concept. Blood, he shows, does not drift in the body in any sort of random ebb and flow. Instead it is pumped endlessly round a very precise circuit.

Until now it has been assumed that the blood in arteries and the blood in veins are different in kind. It is well known that they are of a different colour, and there have been many theories as to what each supply of blood does.

The most commonly held belief is that arterial blood carries some sort of energy connected with air to the body (not far from the truth), and that blood in the veins distributes food from the liver (less accurate).

By a long series of dissections (from dogs and pigs down to slugs and oysters), and by a process of logical argument, Harvey is able to prove that the body contains only a single supply of blood; and that the heart is a muscle pumping it round a circuit.

This circuit, as he can demonstrate, brings the blood up from the veins into the right ventricle of the heart; sends it from there through the lungs to the left ventricle of the heart; and then distributes it through the arteries back to the various regions of the body.

After much initial opposition, Harvey's argument eventually convinces most of his contemporaries. But there are two missing ingredients. His theory implies that there must be a network of tiny blood vessels bringing the blood from the arterial system to the venous system and completing the circuit. But his dissections are not adequate to demonstrate this. It is not till four years after his death that Marcello Malpighi observes the capillaries.

And Harvey is unable to explain why the heart should circulate the blood. That explanation will have to await the discovery of Oxygen.

Malpighi and the microscope: AD 1661

Marcello Malpighi, a lecturer in theoretical medicine at the university of Bologna, has been pioneering the use of the Microscope in biology.

One evening in 1661, on a hill near Bologna, he uses the setting sun as his light source, shining it into his lens through a thin prepared section of a frog's lung. In the enlarged image it is clear that the blood is all contained within little tubes.

Malpighi thus becomes the first scientist to observe the capillaries, the tiny blood vessels in which blood circulates through flesh . They are so fine, and so numerous, that each of our bodies contains more than 100,000 kilometres of these microscopic ducts.

With their discovery, the missing link in Harvey's Circulation of the blood has been found. For the capillaries are literally the link through which oxygen-rich blood from the arteries first delivers its energy to the cells of the body and then finds its way back to the veins to be returned to the heart.

Leeuwenhoek and the microscope: AD 1674-1683

Malpighi's pioneering work with the Microscope is taken further by the Dutch researcher Anton van Leeuwenhoek. Teaching himself to grind lenses to a very high degree of accuracy and clarity (some of them providing a magnification of 300x), he uses a simple Microscope with a single lens - in effect a tiny and extremely powerful magnifying glass.

With instruments of this kind he is able to observe phenomena previously too small to be seen. In 1674 he is the first scientist to give an accurate description of red blood corpuscles. In 1677 he observes and depicts spermatozoa in the semen of a dog. In 1683 he provides a drawing of animalculae (or bacteria) seen in saliva and dental plaque.

His discoveries, published for the most part in the Philosophical Transactions of the Royal Society in London (though he himself lives in Delft), vividly suggest the excitement of being the first to wander with such enlarged vision among the minutiae of the animal kingdom.

His account of the common flea follows its development from egg to the practical perfection of its adult anatomy. His researches demonstrate for the first time that the tiniest living things have a life cycle and generative systems like any larger creature.

Microscopic anatomy: 17th - 20th century AD

With Malphighi's discovery of the capillaries, the major anatomy of the human body is known. With Leeuwenhoek's meticulous study of previously invisible aspects of living material, the subject moves into a more arcane phase - that of microscopic anatomy.

The first great milestones on this new route occur in the 1830s.

Félix Dujardin in 1835 identifies a viscous translucent substance as being common to all forms of life; it is later given the name protoplasm. Meanwhile others observe that living material is organized in a repeated structural form. Robert Brown discovers in plants, in 1831, the nucleus at the centre of every cell. In 1839 Matthias Schleiden and Theodor Swann give the first coherent account of cell formation as the building process of all life (a theme long guessed at by others, but not resolved or demonstrated).

Yet further along this journey, deep into the centre of living matter, is the discovery in 1953 of the structure of DNA.
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