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.
The mesothelium of the serous membrane forms the lining of a closed serous membrane cavity. Serous membrane lining the wall of a serous cavity is designated parietal while that covering viscera is called visceral. Connecting serous membrane runs between parietal and visceral components. The serous membranes are: