He+would+put+his+snout+to+the+ground,+give+several+deep+sniffs,+ad+exclaim+in+a+terrible+voice,

The language here shows extreme description. The visualization and imagery given here states that even though it is mentioned as a "he", through the word "snout", we are able to conclude that this animal is a pig, because pigs have snouts. Not only that, because lots of negative statements has been mentioned about the farm in the passage, we are also able to conclude that this pig is Snowball instead of Napoleon, because the inspection of this snout and realizing a negativity through this smell can only be Snowball. The fact that the author used "he" as a pig and used the word "snout" to describe that this animal is a pig is very descriptive fundamental for the story and its importance in imagery.