In literature, a literary element that establishes a certain atmosphere and evokes certain feelings is called the mood. By the author's choice of words, the readers can easily assume if the mood in the story is depressing, melancholy, cheerful, etc.
In this particular paragraph from Margaret Frink's memoir, the narrator is shocked upon seeing a large number of dead animals by the road. The very description of the animal bodies that lie dead indicate that the mood of this excerpt is horrifying.