What drowns the "ceremony of innocence" in The Second Coming?

I moved this to the Yeats poem because the image is
derived from his work.  In "The Second Coming," Yeats discusses what he feels best
describes the modern setting with a series of images that reflect a sense of crisis and
decline.  One of these images concerns the "ceremony of
innocence:"

The blood-dimmed tide is loosed, and
everywhere
The ceremony of innocence is
drowned;

For Yeats, this image is critical in
addressing the condition of disintegration that Yeats sees all around him following the
First World War.  The "ceremony of innocence" refers to a practice of purity, of a rite
of passage, and of something that represents a structure and order.  Ceremonies of
innocence are those that are rooted in a transcendent condition that provides meaning. 
It is for this reason that madness and disorder have "drowned" the "ceremony of
innocence." The idea of "drowning" helps to bring out that disorder and chaos have
enveloped the hope of structure, the "ceremony of innocence."