In Chapter 12, having run away from Dr. Moreau's house, Prendick finds himself among the Beast Folk. He uses a simile to describe one of the creatures:
THEN SOMETHING cold touched my hand. I started violently, and saw close to me a dim pinkish thing, looking more like a flayed child than anything else in the world. The creature had exactly the mild but repulsive features of a sloth, the same low forehead and slow gestures.
This creature, who Prendick will later refer to as the Pink Sloth Creature, first looks to him "like a flayed child," meaning a child whose skin has been stripped off. This horrifying simile emphasizes the disgust Prendick feels toward the Beast Folk. The reader has likely never seen a flayed child, but imagining this sight evokes the level of disgust and horror Prendick wants to share. The simile also emphasizes that Prendick sees the Beast Folk as human-like first, before he recognizes their animal qualities. This creature looks to him first like a child, and only then like a sloth. This difficulty placing the Beast Folk among animals may in part be because he does not yet know what Moreau's process is. He still believes the Beast Folk are humans who have undergone surgical modifications to look more like animals. His difficulty identifying the Beast Folk by their animal origins is also a testament to how drastically Moreau has modified them. This creature is not immediately recognizable as a sloth walking upright because vivisection has so altered the form of the sloth.
On top of all this, Prendick's difficulty in recognizing whether these creatures are fundamentally human or animal adds to the novel's overall sense that distinguishing between humans and animals is a sticky ethical problem that individual humans cannot very well solve. It is uncanny for Prendick to see a creature who looks at once like a child, a sloth, and neither because this creature inherently destabilizes the categories of human and animal. Prendick's sense of disgust has as much to do with being confronted with the ethics of classification as with the Pink Sloth Creature itself.
In Chapter 22, Prendick describes his return to England after he escapes from the island and is rescued at sea. He uses a simile to describe a "delusion" he has about the people there:
I would go out into the streets to fight with my delusion, and prowling women would mew after me, furtive craving men glance jealously at me, weary pale workers go coughing by me, with tired eyes and eager paces like wounded deer dripping blood, old people, bent and dull, pass murmuring to themselves, and all unheeding a ragged tail of gibing children.
Prendick's time on the island essentially turns him into a misanthrope. He does not believe that the people in England are really going to start behaving like bloodthirsty animals, but he has such a deep paranoia about it that he can hardly bear to live among them. Here, he compares the working class to "wounded deer dripping blood," presumably because they are being preyed upon by the people and systems exploiting them. Just as a predator in the woods might attack a deer without concern for its quality of life if it survives, society leaves the working class to struggle along on the brink of death. Although Prendick describes fighting his "delusion," this simile suggests that he might not be as delusional as he thinks. There were some protections for laborers in England by the time Wells wrote this book, but a great many protections had yet to be passed. The working class really were being preyed upon, much like prey animals in nature. Prendick is once again revealing himself to be an unreliable narrator, but this time it is because he doesn't see how right he is about the world.
Prendick's time on the island traumatizes him, but it also allows him to see English society as the wild and vicious ecosystem it is. It is significant especially that Wells draws attention to the working class given his interest in this novel and elsewhere (especially The Time Machine) with class uprisings. Wells had the sense that the working class was going to rebel against the ruling class sooner or later unless they were given more social safety nets. The political history of the 20th century is extremely complex, but Wells was correct that wealth disparity would lead to major conflict in the decades to come.
