|
||||||||
The germ theory of diseaseEver since the earliest times infectious diseases have brought death and devastation wherever they are found across the globe. People were often desperate to find ways to prevent the spread of these diseases, which were generally incurable until the discovery of antibiotics. For centuries, however, thinking about disease was limited because no-one really understood how the causes of diseases or how they were spread. But by the 19th century ideas were beginning to change. People didn't find it easy to accept the idea that infectious diseases were brought about by an infectious agent (or 'germ') which was passed from one individual to another and caused disease. And it wasn't until people realised that infectious diseases were caused by microorganisms that they could really hope to find a cure for the diseases. Some of the steps on the way to the acceptance of germ theory are descibed below : The work of Ignaz Phillipp Semmelweiss in the mid 1850s on preventing
the death of women from childbed fever in the days after giving birth.
He realised that in the hospital where he worked the medical students
were often dissecting a dead body as part of their training and then
moving straight on to delivering a baby without washing their hands
first. He wondered if they were carrying the cause of disease on their
hands from the corpses to their patients. Then a colleague cut himself
whilst carrying out an autopsy and subsequently died from symptoms identical
to those of childbed fever. For Semmelweiss this confirmed his idea
that childbed fever was caused by an infectious agent. Some European doctors and church men thought that childbed fever was God's punishment to women for the act of giving birth. To change their point of view would mean accepting that the deadly disease was caused by an invisible something which could be transferred from patient to patient. But more than that, it was hard for doctors to admit that they themselves had spread the disease and killed their patients instead of curing them. Also handwashing probably seemed rather an odd practice at the time. There was no indoor plumbing, so getting water to wash in was not easy, the water was cold, and the chemicals used for washing eventually damaged the skin of the hands. It is difficult to imagine from the 21st century just how difficult such a simple act must have seemed in the 19th century! In 1857 Louis Pasteur proved that the air was full of microbes which would grow in the right conditions. He did a series of classic experiments with swan necked flasks which showed that the microorganisms which grew in broth, turning it cloudy and mouldy, did not appear from nowhere at the will of God but were already present in the air. Over three years of study between 1865 and 1868 Pasteur showed that a mysterious disease of silkworms which swept France could be controlled by destroying infected insects. Pasteur also showed that keeping healthy eggs away from all contact with living caterpillars made sure the eggs would produce healthy moths - the disease was caused by 'germs'. Joseph Lister was a Scottish surgeon who read some of Pasteur's work on germ theory in fermentation and made the mental leap that it might be similar 'germs' which cause infection. In 1874 he developed the use of carbolic acid to kill those germs and so prevent infection during and after surgery. In Lister's wards instruments, dressings and the surgeons themselves were sterilised in carbolic solution before an operation - and Lister's patients stayed healthy, without infection. Lister wrote to Pasteur to thank him for his help and to tell him how he had discovered a way of killing germs. Pasteur showed that the killer disease anthrax was passed from animal to animal by infectious organisms ('germs') and used these to produce a vaccine. 1n the 1870s up to 50% of all the sheep and cattle in France were dying of anthrax - Pasteur saved the French farmers from disaster. Pasteur and his team were confident that they could find a way of beating anthrax - but it proved more difficult that they thought. Anthrax is highly infectious - animals have only to graze over the burial site of anthrax victims and they have a strong chance of catching the disease. Pasteur showed that an infectious agent was being brought up from the bodies by worms as they mixed the soil. But the anthrax germ proved very hard to grow in the laboratory and making a reliable vaccine proved difficult. Then in 1881 a vet who had little time for the germ theory of disease threw down a very public challenge to Pasteur to test out his vaccine. Rather than appear unsure of his work, Pasteur accepted the challenge. His vaccine worked - his vaccinated sheep survived the injection of live anthrax spores! The vaccine had a major effect on farming for generations to come - but the proof it gave of the germ theory of disease was to have even greater implications for the health and well being of people all over the world. Robert Koch was the other key worker who helped to build up the evidence for the final complete acceptance of the germ theory. Robert Hooke had developed the first microscope in 1665 and in the years which followed cells were seen for the first time. But it was not until the later part of the 19th century that microscopes developed to the point where it was possible to see bacteria for the first time . In the 1870s and 80s Robert Koch used these new, more powerful microscopes to see and identify the bacteria which caused a number of important diseases including anthrax, tuberculosis and cholera. More than this, he observed the germs multiplying and investigated the conditions which would stop them reproducing. By the end of the 19th century the idea that infectious diseases were caused by germs was almost universally accepted.
|
||||||||
|
||||||||
ctivity
1
Finding out about Fleming
