Sentence:  We believe this to be the true way to teach zoölogy, for we doubt the value to a man of a mass of indefinite ill-digested text-book information. Occasionally an omnivore can take in every thin, and digest and so <WSD>metabolize</WSD> it as to organize it into healthy mental tissue. They are, however, the few. 
Meaning of the word marked with <WSD> tags:  To absorb and process as if by metabolism.