How does the author use imagery in the novel, The Netanyahus?

Imagery:

“…biology and chemistry professors pass away and decompose into biology and chemistry, they mineralize into geology, they disperse into their science, just as surely as mathematicians become statistics. The same process holds true for us historians—in my experience, we’re the only ones in the humanities for whom this holds true—the only ones who become what we study; we age, we yellow, we go wrinkled and brittle along with our materials until our lives subside into the past, to become the very substance of time.”