How is the theme of the power of words developed in Animal Farm?

In the first chapter, Old Major gives a speech to the other animals to inspire them and encourage a revolution. He explains that man (humans) are the cause of their miseries and determines that a revolt is necessary to improve their lives. He establishes the commandments of Animalism which set up a framework for the improvement of their lives. He then sings "Beasts of England" which is like a national anthem for the animals. The...

In the first chapter, Old Major gives a speech to the other animals to inspire them and encourage a revolution. He explains that man (humans) are the cause of their miseries and determines that a revolt is necessary to improve their lives. He establishes the commandments of Animalism which set up a framework for the improvement of their lives. He then sings "Beasts of England" which is like a national anthem for the animals. The animals are inspired and excited with Old Major's reasoning and his encouragement. The song sends them over the top. This shows the power of words in speech and in song: 

The singing of this song threw the animals into the wildest excitement. Almost before Major had reached the end, they had begun singing it for themselves. 

Throughout the novel, the experiment of Animalism grows steadily worse. As Napoleon gains more power, he has Squealer change the written commandments in order to suit his desire for more power. This is done one commandment at a time, a sly way of changing the laws subtly enough that no animals might notice. The last commandment Old Major gives in Chapter 1 is "All animals are equal." In Chapter 10, after Napoleon has already changed some commandments, he changes this to "All animals are equal. But some animals are more equal than others." In other words, the pigs are superior to all other animals. Each time Squealer changes the commandments, the law of the land changes. The living conditions of the animals change as well. This shows the power of the written word and of written laws. This shows how written words and laws directly affect lives.