It is an informal, somewhat grotesque choice of expression, in a paragraph marked by grotesquerie.

The phrasal verb "spit out" refers to ejecting something from the mouth, and is used as an informal figure of speech of devices and machines and processes. 

A parent might say to a toddler who has put a penny in their mouth, "Spit it out". That is how it is used literally.

Figuratively, for example,  a toll booth on a turnpike might be said to "spit out a ticket".  Or someone can complain that an ATM machine "didn't spit out my card". Someone could speak derisively of a prolific hack author, saying  "she spits out a bodice ripper every quarter."