In Animal Farm, the corruption of the revolution and of the principles of Animalism occurs in several ways simultaneously. The pigs break both the letter and the spirit of the Seven Commandments, then revise them, and finally get rid of them altogether.
In chapter 6, it becomes clear to all the animals that the pigs have adopted human habits, living inside the farmhouse, eating in the kitchen, and sleeping in the beds. These actions contravene the spirit of Animalism, but the last of them also breaks a specific Commandment. However, when Muriel reads out the Fourth Commandment, which forbade sleeping in a bed, she finds that the words "with sheets" have been added to the end. Squealer then tells the other animals that the pigs have removed the sheets from the beds, and now sleep between blankets.
The rules of Animalism are broken in less specific ways throughout chapters 6 and 7. The pigs engage in trade with humans, and take away the hens' eggs, which the hens regard as murder. When they rebel, Napoleon stops their rations and makes it an offense punishable by death to give them any food. These actions break the Sixth Commandment, which stipulates that no animal shall kill any other animal.