The one about the graveyards is by Georges Clemenceau, the French WW-I prime minister. His party wanted to discourage his retirement. He responded with the quoted words, adding "...who have been replaced".
For #45, technically the Poem is called Song of Myself and the Collection is Leaves of Grass, so while it is in Leaves of Grass, it is more specifically found in the poem Song of Myself, which was collected in Leaves of Grass
The best lack all conviction, while the worst
Are full of passionate intensity.