LEONARDO DA VINCI (1452-1519)

1502 – Florence, Italy

‘In the Renaissance science was reinvented’

Image of the VITRUVIAN MAN

VITRUVIAN MAN

Leonardo is celebrated as the Renaissance artist who created the masterpieces ‘The Last Supper’ (1495-97) and ‘The Mona Lisa’ (1503-06). Much of his time was spent in scientific enquiry, although most of his work remained unpublished and largely forgotten centuries after his death. The genius of his designs so far outstripped contemporary technology that they were rendered literally inconceivable.

The range of his studies included astronomy, geography, palaeontology, geology, botany, zoölogy, hydrodynamics, optics, aerodynamics and anatomy. In the latter field he undertook a number of human dissections, largely on stolen corpses, to make detailed sketches of the body. He also dissected bears, cows, frogs, monkeys and birds to compare their anatomy with that of humans.

It is perhaps in his study of muscles where Leonardo’s blend of artistry and scientific analysis is best seen. In order to display the layers of the body, he developed the drawing technique of cross-sections and illustrated three-dimensional arrays of muscles and organs from different perspectives.

Leonardo’s superlative skill in illustration and his obsession with accuracy made his anatomical drawings the finest the world had ever seen. One of Leonardo’s special interests was the eye and he was fascinated by how the eye and brain worked together. He was probably the first anatomist to see how the optic nerve leaves the back of the eye and connects to the brain. He was probably the first, too, to realise how nerves link the brain to muscles. There had been no such idea in GALEN’s anatomy.

Possibly the most important contribution Leonardo made to science was the method of his enquiry, introducing a rational, systematic approach to the study of nature after a thousand years of superstition. He would begin by setting himself straightforward scientific queries such as ‘how does a bird fly?’ He would observe his subject in its natural environment, make notes on its behaviour, then repeat the observation over and over to ensure accuracy, before making sketches and ultimately drawing conclusions. In many instances he would directly apply the results of his enquiries into nature to designs for inventions for human use.

Self portrait of LEONARDO DA VINCI

LEONARDO DA VINCI

He wrote ‘Things of the mind left untested by the senses are useless’. This methodical approach to science marks a significant stepping-stone from the DARK AGES to the modern era.

1469 Leonardo apprenticed to the studio of Andrea Verrocchio in Florence

1482 -1499 Leonardo’s work for Ludovico Siorza, the Duke of Milan, included designs for weaponry such as catapults and missiles.
Pictor et iggeniarius ducalis ( painter and engineer of the Duke )’.
Work on architecture, military and hydraulic engineering, flying machines and anatomy.

1502 Returns to Florence to work for Pope Alexander VI’s son, Cesare Borgia, as his military engineer and architect.

1503 Begins to paint the ‘Mona Lisa’.

1505-07 Wrote about the flight of birds and filled his notebooks with ideas for flying machines, including a helicopter and a parachute. In drawing machines he was keen to show how individual components worked.

1508 Studies anatomy in Milan.

1509 Draws maps and geological surveys of Lombardy and Lake Isea.

1516 Journeys to France on invitation of Francis I.

1519 April 23 – Dies in Clos-Luce, near Amboise, France.

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WILLIAM HARVEY (1578-1657)

1628 – London, England

‘Circulation of the blood’

Portrait of WILLIAM HARVEY ©

WILLIAM HARVEY M.D.

As WILLIAM GILBERT had begun in physics, and FRANCIS BACON had subsequently implored, Harvey was the first to take a rational, modern, scientific approach to his observations in biology. Rather than taking the approach of the philosophers, which placed great emphasis upon thinking about what might be the case, Harvey cast aside prejudices and only ‘induced’ conclusions based on the results of experiments and dissections, which could be repeated identically again and again.

After what GALEN had begun and VESALIUS had challenged, Harvey credibly launched perhaps the most significant theory in his field of biology. He postulated and convincingly proved that blood circulated in the body via the heart – itself little more than a biological pump.

Galen had concluded that blood was made in the liver from food, which acted as a fuel, which the body used up, thereby requiring more food to keep a constant supply. Vesalius added little to this theory. Harvey, physician to Kings James I and later Charles I proved his theory of circulation through rigorous and repeated experimentation. He correctly concluded that blood was not used up, but is recycled around the body.

An illustration depicting William Harvey (April 1, 1578 - June 3, 1657), the medical doctor credited with first describing the properties of the human circulatory system, seeing a patient. ©

 

His dissections proved that the arteries took blood from the heart to the extremities of the body, able to do so because of the heart’s pump-like action. He could see that the pulses in arteries came immediately after the heart contracted, and became certain that the pulse was due to blood flowing into the vessels.
By careful observation he found that blood entered the right side of the heart and was forced into the lungs, before returning to the left side of the heart. From there it was pumped via the aorta into the arteries around the body.

Harvey realized that the amount of blood flowing around the system was too much for the liver to produce. The blood had to be circulating back to the veins; which, with their series of one-way valves, brought blood back to the heart.
Without a microscope it was impossible to see the minute capillaries that linked the arteries to the veins.

Exercitatio anatomica de motu cordis et sanguinis in animalibus William Harvey (1628)

Harvey published his findings in the 720 page ‘Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus‘ ( Anatomical Exercise on the Motion of The Heart and Blood in Animals ) at the Frankfurt Book Fair in 1628.

Initially supported by some academics, an equal number rejected his ideas. One area of weakness was that he was unable to offer a proven explanation for how the blood moved from the arteries to the veins. He speculated that the exchange took place through vessels too small for the human eye to see, which was confirmed shortly after his death with the discovery of capillaries by Marcello Malphigi with the recently invented microscope.

Even then, nobody knew what blood was doing. It would take another hundred years before ANTOINE LAVOISIER discovered oxygen and worked out what it did in the body.

In 1651, Harvey published ‘Exercitationes de Generatione Animalium‘ ( Essays on the Generation of Animals ), a work in the area of reproduction which included conjecture that rejected the ‘spontaneous generation’ theory of reproduction which had hitherto persisted. His belief that the egg was at the root of life gained acceptance long before the observational proof some two centuries later.

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Related sites
  • The Old Operating Theatre (www.thegarret.org.uk)