HISTORY OF MEDICINE
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.
Blood transfusion: AD 1665-1670
At a meeting of the recently established Royal Society in London, on 14 November 1665, an experiment is made in transferring blood from one dog to another. The artery of a small mastiff is joined by a quill to the vein of a spaniel. Another of the spaniel’s veins is opened to let out an equivalent amount of its own blood.
The mastiff bleeds to death in front of the Society. The spaniel is produced at the equivalent meeting a week later and is found to be in fine health.
Two years later, in France, a much more ambitious step is taken along these same lines. Jean Baptiste Denis, royal physician to Louis XIV, conducts a bold experiment in 1667 in Paris. In an attempt to save the life of a 15-year-old boy, weakened by too much blood-letting, he inserts into his veins, through a quill, about half a pint of the blood of a lamb.
Contemporary reports say that the condition of the boy is greatly improved.
Later in the same year, following this impressive example from Paris, the Royal Society in London becomes more bold in its experiments. Arthur Coga, a divinity student from Cambridge who is said to be slightly ‘frantic’, is hired for a transfusion. Half a pint of sheep’s blood is passed into his vein. The scientists hope that this will cool his own blood and thus make him less frantic.
Opinions differ as to whether this desirable effect is achieved. When asked why he has received sheep’s blood, rather than that of any other creature, the divinity student replies that it is because Christ is the Lamb of God.
A week later Mr Coga addresses the Society in Latin and declares that he feels much better. Later on the same day Pepys meets him at dinner and still finds him ‘cracked a little in his head’. Pepys is rather shocked to hear that Coga ‘had but 20 shillings for his suffering it, and is to have the same again tried on him’. He receives a second transfusion three weeks after the first, and apparently experiences no lasting ill effects.
Pepys says that Coga is the first healthy man to have had the experiment tried upon him, apart from a porter in France hired for the same purpose ‘by the virtuosi’. But a disaster in France is about to put an end to this run of experiments.
Following his success in 1667, Jean Baptiste Denis has given blood to several other patients with continuing success. But in 1668, after a third transfusion, one of his patients dies. Denis is sued by the widow. He loses the case, though he is cleared of murder.
The result is that the entire experiment falls into disrepute, after a turmoil of excitement lasting three years. In 1670 a law is passed in France making blood transfusion illegal. For another two centuries no more is heard of it anywhere – until it is again attempted fairly regularly in mid-19th century England, now usually with human blood. But it remains a hazardous procedure until the discovery, in 1900, of the human blood groups.
Inoculation: 17th – 18th century AD
At some time before the end of the 17th century a bold procedure, possibly practised already for several centuries in parts of Asia, becomes established in Turkish medicine. It is the use of inoculation to protect against the extremely infectious and frequently fatal disease of smallpox.
Inoculation is based on an easily observed medical fact – that those who contact an infectious disease and survive are protected against catching it again. Inoculation is a precautionary measure, though in the case of smallpox a dangerous one.
Pustulent matter from the skin of a lightly infected smallpox victim is rubbed into a fresh scratch in the skin of the person being inoculated, with the intention of inducing a mild attack of the disease. Most of those undergoing the treatment survive and are protected. The unfortunate few die.
The procedure reaches Europe because of a sequence of events in the early 18th century. In 1715 Lady Mary Wortley Montagu, a young beauty and wit in fashionable London, catches smallpox. She survives but is left with disfiguring scars. A year later her husband is appointed ambassador to the court of the Turkish sultan. She accompanies him to Istanbul, together with their three-year-old son.
In Istanbul she sees inoculation successfully carried out. Her own recent experience prompts her to a possibly reckless decision. She submits her infant son to this Turkish procedure. He survives. Back in London, in 1718, Lady Mary has a second child, a daughter. She has this child inoculated in England. She too survives.
With characteristic vigour Lady Mary now begins campaigning for this basic measure of preventive medicine. She has sufficient success for inoculation to become an increasingly common practice in England during the 18th century. But it remains, inevitably, a hazardous one – until Edward Jenner discovers a safer method.
