At the beginning of Chapter 10, years have passed since the initial years of the rebellion. Many of the animals who had been part of the rebellion are gone or dead. Therefore, most of the ideals and promises of the revolution are gone as well. The younger animals simply accept Napoleon's historical account and the way he runs the farm. In many ways, the animals are now worse off under Napoleon than when Mr. Jones ran the farm. The windmill is not used for the benefit of the animals. Instead, it is used to mill corn and increase profits. The pigs, under Napoleon, have become just as bad, if not worse, as the humans. The commandments have been changed so that some animals (namely, the pigs) are considered superior to the other animals:
ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS.
The pigs have begun to wear human clothing. By the end of the novel, the other animals can not tell the difference between the pigs and the humans:
The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.
The pigs had become just as corrupt as the humans they replaced. The initial motivation of the rebellion was to make the lives of the animals better. However, enjoying power as much as their human predecessors, Napoleon and the pigs became just as corrupt; therefore, the other animals could not tell the difference between pigs and humans.
The significance lies in the comment that the animals could not tell the difference between the pigs and the humans. Reflect back to the speech by Old Major where he warns the animals that in fighting against man they must never take on human vices and resemble them.