In the 19th century, surgical hygiene got better because of asepsis. Doctors realized that dirtiness and germs cause infections, so they started to keep things cleaner and do things to kill germs in order to prevent their patients from getting infections. It became more common for people to survive after having surgery. Surgical removal of the tumor (taking the tumor out of the body by doing surgery) became the first-choice treatment for cancer. For this kind of treatment to work, the surgeon doing the operation had to be very good at removing tumors. (This meant that even if people had the same kind of cancer, they could get very different results, with some getting good treatment that worked and others getting treatment that did not work, because of differences in how good different surgeons were.)
In the late 1800s, doctors and scientists started to realize that the body is made up of many kinds of tissues, which in turn are made up of millions of cells. The discovery started the age of cellular pathology (studying cells to learn about diseases and figure out what is wrong with the body).
In the 1890s, French scientists discovered radioactive decay. Radiation therapy became the first cancer treatment that worked and did not involve surgery. It required a new multi-disciplinary approach to cancer treatment (people doing different jobs were working together to treat patients). The surgeon was no longer working by himself - he worked together with hospital radiologists (people who gave and read X-rays) to help patients. This team approach meant changes in how they worked. The different people on the team had to communicate with each other and work together, which they were not used to doing. It also meant that treatment had to be done in a hospital rather than at the patient's home. Because of this, patients' information had to be put together into files kept at the hospital (called "medical records"). Because this information was now being kept and written down, scientists were able to do the first statistical patient studies using numbers to study questions like how many people who have a certain type of cancer or get a certain treatment survive.
Another important step forward in understanding cancer happened in 1926, when Janet Lane-Claypon published a paper on cancer epidemiology. (Epidemiology is a field of study which looks at how common a disease is, what patterns the disease takes in different kinds of people, and what this means for understanding and treating the disease.) This historic paper was a comparative study, which tries to find out what causes a disease by looking at a group of people who have the disease and figuring out how they are different from another group that does not have the disease. Lane-Clayton's study looked at 1000 people who all had the same background and lifestyle (or way of living): 500 people with breast cancer and 500 control patients (people without breast cancer). These people were the same in many ways, but some got breast cancer and some did not. To figure out what might be causing certain people to get breast cancer, the study looked at what was different about these people when they were compared to (or looked at alongside) the people who did not get cancer.
Lane-Clayton's study was published by the British Ministry of Health. Her work on cancer epidemiology was continued by Richard Doll and Austin Bradford Hill. They used the same ways of studying cancer as Lane-Clayton, but they looked at a different kind of cancer: lung cancer. In 1956, they published their results in a paper called "Lung Cancer and Other Causes of Death In Relation to Smoking. A Second Report on the Mortality of British Doctors" (also called the British doctors study). Later, Richard Doll left the London Medical Research Center (MRC), and started the Oxford unit for Cancer epidemiology in 1968. By using computers, this unit was able to do something new and very important: it brought together large amounts of cancer data (pieces of information about cancer). This way of studying cancer is very important to cancer epidemiology today, and it has also been very important in shaping what we now know about cancer and what the rules and laws about the disease and public health are today. Over the past 50 years, many different people have done a lot of work to collect data from different doctors, hospitals, areas, states, and even countries. This data is used to study whether different kinds of cancer are more or less common in different areas, environments (for example, in big cities compared to the countryside), or cultures. This helps people who study cancer to figure out what makes people more or less likely to get different kinds of cancer.
Before World War II, doctors and hospitals were getting better at collecting (or getting and keeping) data about their patients who had cancer, but it was rare for this data to be shared with other doctors or hospitals. This changed after WWII, when medical research centers found out that different countries had very different number of cases of cancer. Because of this, many countries created national public health organizations (which studied public health issues in an entire country). These national public health organizations began to bring together health data from many different doctors and hospitals. This helped them figure out some of the reasons why cancer was so much more common in certain places. For example, in Japan, people studying cancer found out that people who had survived the atomic bombings of Hiroshima and Nagasaki had bone marrow that was completely destroyed. This helped them realize that diseased bone marrow could also be destroyed with radiation, which was a very important step in figuring out that leukemia (a blood cancer) can be treated with bone marrow transplants.
Since World War II, scientists have kept finding better cancer treatments. However, there are some things that still need to get better. For example, while there are good treatments for many kinds of cancer, there are still no treatments for certain kinds of cancer, or for some cancers once they progress (or get worse) to a certain stage of the disease. Also, the cancer treatments that do exist are not all standardized (there is not one agreed-upon way of giving every treatment which is used each time the treatment is given). Cancer treatments are also not available everywhere in the world. People need to keep studying cancer epidemiology and forming international partnerships (where different countries work together) to find cures and make cancer treatments available everywhere.
Photography
Photography is a way of making a picture using a camera. A person who makes pictures using a camera is called a "photographer". A picture made using a camera is called a photograph or photo. Photography became popular in the middle 19th century with Daguerreotype. Later wet plate and dry plate methods were invented. Most photography in the 20th century was on photographic film and most in the 21st uses digital cameras.
A "camera" is, in its simplest form, like a box with a hole in front of it. There is a special piece of glass in front of the hole called a lens. To take a photograph of something, the lens makes a small picture of the object inside the box. The lens does this by focusing light. A lens in a camera works like a lens in glasses (spectacles) or a magnifying glass. One type of camera called the Pinhole camera has no lens but uses a very small hole to focus light.