Mark Twain, "A Dog’s Tale" (1903) from Mark Twain: Collected Tales, Sketches, Speeches, & Essays 1891–1910:
A curious story: the first two pages are pure comedy, about a dog who doesn't understand big words but pretends to and impresses all the other dogs in the community--who also don't understand the words. But after those two pages, we have nine pages steadily sliding into drama and sentimentality: the pup of that dog didn't learn the language, but learned to behave correctly from its mother. So that when it finds itself in a good house with a good family, it knows to risk its life to save the baby from a fire. After that, the scientific-minded father misunderstands and hurts the dog's leg. And later, he experiments on the savior dog's puppy, resulting in blindness and death for the puppy; and depression, loss of appetite, and death for the narrator dog.
The story, in its way, reminds me of Wells's 1896 Island of Doctor Moreau, another story that mixes in some pleasant diversion (adventure in Wells, comedy in Twain) along with some questioning about the relations of people and animals; the "humanity" of animals--such as their ability to feel pain both physically and emotionally; and the use of animals in scientific experimentation. It's curious to see these two men work through some of the same issues in their different ways.
But getting back to Twain alone, we can see how he forwards his position through some rhetorical (and narrative) tools here: putting us in the dog's POV from the first and giving us some doggy faults that help develop our empathy (since, frankly, we like people who aren't perfect--and that goes for dogs too); following in some fairly traditional tropes, like the dramatic irony of the dog hiding after doing something heroic because it misunderstands what it did--alongside the master's own misunderstanding of what the dog did; and, that old standby, surrounding the main actors with some minor characters to present the thematic or ethical approach. That is, here, the servants and children make no bones about the dog being the best, most loyal dog in the world; and they go on about it being a shame that dogs don't go to heaven--even while the story makes the case that they should.