An agent that is smaller than a virus causes scrapie. It is either a protein called a prion or it is another substance closely associated with the prion protein. Scientists still have a lot to learn about the scrapie agent and exactly how it works.
Tissue valves are made with tissues from porcine (pig) heart valves or bovine (cow) cardiac tissue because they function like human heart valves. Once the tissue is removed from the animal, it is chemically treated to preserve the tissue and prevent immulogic reactions once it is placed in a patient.
Recycled toilet paper. Toilet tissue made from recycled paper is made from both colored and white stock, with staples and pins removed. The paper goes into a huge vat called a pulper that combines it with hot water and detergents to turn it into a liquid slurry.