The body politic
In Act I scene i, in order to calm down the rebellious plebeians, Menenius tells them the fable of the belly. He says that in the human body, the belly is the storehouse for the food, and sends nourishment to all the body's parts. By analogy, the senators (heads of state) of Rome are the belly, and the plebeians are the mutinous other parts of the body. Every benefit the plebeians receive comes from the senators, who collect it but then distribute it.
The fable refers to the concept of the body politic, a traditional way of likening the functioning of the state to that of the human body. The body politic assumes that the state has an organic nature, just as the body does, and that therefore certain political structures and actions are appropriate. A "natural?society is viewed as functioning in a manner similar to the human body. Though this idea has been used to support a variety of governmental types, in general, these governments are hierarchical and authoritarian, stressing social order and obedience to those in power.
It soon becomes clear in Coriolanus that the body politic has broken down, and neither the patricians nor the plebeians are wholly innocent or wholly at fault. If the plebeians are rebellious, the patricians are neglecting their duty to take care of and nourish the plebeians. The First Citizen emphasizes this in his speech at I.i.67?2: "Care for us? ?They ne'er cared for us yet. Suffer us to famish, and their storehouses crammed with grain ." On the individual level, Coriolanus's pride and disdain for the plebeians cuts him off from them in a manner that is destructive to both sides. This breakdown in the relationship between patricians and plebeians is as dangerous to the health of society as a breakdown in the relationship between belly and body parts would be to the health of a person.
In addition, Shakespeare suggests through imagery that the plebeians, without strong governance from the patricians, are incomplete men, like body parts separated from the whole organism. Menenius calls the First Citizen "the great toe of this assembly?(I.i.141); Coriolanus dismisses their truisms as "shreds?(I.i.194). Stretching the fragmented imagery to clothes, Coriolanus refers to their "cobbled?(patched together) shoes (I.i.182).
Hydra, or monstrous body
A variant on the body politic metaphor is the monstrous body, or Hydra, to which Coriolanus likens the plebeians. The Hydra was a mythical poisonous water-snake with many heads. This metaphor is repeated several times in the play to refer to the mob (see, for example, "the many-headed multitude at II.iii.15). If a well-ordered state is portrayed as a healthy human body, the disorder and fickleness of the plebeians is portrayed as a monstrous body ?the dangerous and unpredictable Hydra. The particular horror of the Hydra lay in the fact that if one of its heads were cut off, it would grow another or several in its place. Coriolanus's likening of the mob to the Hydra expresses the fear felt by the ruling class of both ancient Rome and Elizabethan England that the people, once given power, would prove ungovernable because of their greater number and their natures unsuited to leadership. The consequence would be, so it was thought, the destruction of the state. This view is validated in this scene by the eagerness of the tribunes to dismiss due process of law: they proclaim Coriolanus a traitor and condemn him to death without a trial.
Another variant on the metaphor of the body politic is that of the diseased body. Coriolanus refers to the mob as a disease, "measles?(III.i.78). When they express their discontent, he says they are "rubbing the poor itch of [their] opinion?so that they "Make [themselves] scabs?(I.i.151?52). Their desires, he says, are "A sick man's appetite, who desires most that / Which would increase his evil?(I.i.164?65). Typically of this ambivalent play, however, the metaphor of the unhealthy body is also used against Coriolanus. Sicinius calls Coriolanus "a disease that must be cut away?(III.i.293) and refers to his mind as "a poison?(III.i.87). Brutus dismisses Menenius's insistence on peaceful and legal processes to try Coriolanus as "cold ways?that "are very poisonous / Where the disease is violent?(III.i.219-221). This is a reference to the Renaissance doctrine of "humors?or bodily fluids, where disease was seen as an excess of hot or cold humors, and medicines that were hot or cold in nature were prescribed to cure it.