Answer:
Central idea expresses the theme of the poem.
In this straightforwardly iambic line, Richard extends the metaphor by comparing the erstwhile reign of Lancaster to the gloom of a cloudy sky, playing upon the "sun of York" line that precedes it. Lour'd—Shakespeare uses the apostrophe to signal that "loured" should absolutely not be pronounced as "louréd"—is an archaism (from the Middle English louren; probably deriving from Middle High German luren "to lie in wait") that meant "to look sullen; to frown upon." The reference to "our house" refers primarily to the family of York, although it could also play off one of its meanings as "the management of domestic affairs" (referring to the War of the Roses).
The main idea is basically it is informing you that animals are simply in the hospital to help patients.
