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 membranes are continuous but when the membrane covers the wall of the body cavity it is called parietal and when the serous membrane lines an organ within the body cavity it is called visceral (viscus is Latin for organ). The word serous means watery.