The old horse is a reference to Argos, Odysseus’s dog. When Odysseus returns from the Trojan War, he finds Argos on top of a pile of cow manure, looking old and sick. Thus, Odysseus’s meeting with Argos shows how his duty to fight in the war has tragically prevented him from taking care of the people most loyal to him. Arguably, this is similar to the relationship between Bloom (who loyally takes care of Stephen) and Stephen (who ignores Bloom because he’s focused on his artistic calling). Of course, this horse is also a reference to the Ascot Gold Cup horserace, which Bloom’s alter ego Throwaway managed to win at the last moment. Besides referring to the “Sirens” episode, Stephen’s song is also a metaphor for Bloom’s distance from Molly, the lure of the exotic, and the temptation of selling out to become a commercial artist. The defecating horse is typical Joyce. Ironically, it’s cleaning and dirtying the streets at the same time. Its three turds might represent the triad of Stephen, Molly, and Bloom, or the unholy trinity of Buck Mulligan, Haines, and Stephen. This may also be a metaphor for Stephen’s feelings about Bloom’s proposal that he should sing commercially.