The speaker looks at the heart without any of the usual sentiment. It becomes "a great jar of blood," something known only by hearsay, and the poem wonders whether having one is even a benefit. The heart can't be a friend or feel delight, and it doesn't think. It simply works, and in the end it looks like meat. The tone is cool, almost clinical, as if the speaker is testing how much can be taken away from a symbol we normally treat so tenderly.
Then the setting arrives: "a funeral." That seems to explain the bleakness, since death makes the body look like a mechanism that has stopped. But the last lines turn. Love, the speaker says, lives "in the tongue / of a dying shoe." The image is odd and humble, and the poem leaves it unexplained. Judging by the imagery, love survives not in the heart but in worn, ordinary things, or in language. The mood is dry and grieving, with a small, strange warmth at the end.