Which medical term means "inflammation of the membrane that lines the abdominal cavity"?

The answer is Peritonitis. It is the inflammation of the peritoneum, this is the membrane found in the inner abdominal wall. This is caused by some bacteria or fungi. Some of the symptoms are vomiting, nausea, high temperature, swollen abdomen, less urination, lack of appetite. 

It doesn’t show the symbol

When scientist examine data such as historical documents, they are using the "scientific methods"