In addition to water, oxygen, and nutrients, the most important factor for maintaining life is Homeostasis. Homeostasis is best defined as a state of equilibrium in which the internal environment of the body remains relatively constant and/or is maintained. As is the case with the body, any government which wishes to survive must also maintain homeostasis. If the government cannot control or maintain the environment of its state it can cause weakness and subject the government to a number of risks, such as revolution or takeover by a foreign invader. The risks of any government which fails to maintain homeostasis are also synonymous with the risks to a body which fails to do the same as it risks shock (a revolution - sharp and sudden change in which the body operates in an attempt to return to normalcy) and the invasion of a foreign bacteria or virus (which also has the ability to topple the body).
Beyond drawing parallels to just any government, the body also mimics the way in which an ideal democracy operates. For the most part, each cell of the body is equipped with the same chemical messengers, and therefore whenever a cell needs more or less of something it triggers the release of some kind of chemical messenger or protein which is usually in turn relayed to the brain. In this sense every cell gets its own "vote" to how additional resources are spent in the body. What is important to remember here is that some organs have far more cells then others (for example the brain, which has far more cells then any other organ in the body), and when two organs are competing for the same resources, lets say the brain and a kidney, the brain would receive the needed resources because its cells far outnumber the cells of the kidney however, the kidney would not be completely disregarded, it would receive and equal amount on the cellular level but not as much in total as the brain did. A common misconception is that certain body parts are given preferential treatment over others when it comes to distribution of vital supplies which is in fact false, and helps support this model.
