Using some British slang to describe his tattered companion, Mulligan condescendingly exclaims, "Ah, poor dogsbody!" A dogsbody is an individual at the bottom of the institutional pecking order who is assigned the boring, menial, or unpleasant tasks that no one else wants to do. Close American equivalents are “gofer,” “grunt,” and “drudge.” But Stephen takes the phrase literally, sparking a series of meditations on dogs' bodies.

Source: sangrea.net.

Source: www.summerclouds.com.