On Dark Carnival's Stadium Entrance, you can also have another way to summon the Horde. Also in Left 4 Dead 2, there is a new mutation mode called Versus Survival which is a mix of both Survival, and Versus mode.
A serous membrane is a thin membrane that helps body parts move more easily and reduces friction between them. Also known as serosa, these membranes are found throughout the body, usually surrounding organs. There are several medical conditions associated with the serous membane, some of which can be life threatening.
Serous fluid. In physiology, the term serous fluid or serosal fluid (originating from the Medieval Latin word serosus, from Latin serum) is used for various bodily fluids that are typically pale yellow and transparent and of a benign nature. The fluid fills the inside of body cavities.