An artist who takes a bite out of his own painting , and who derives his subject matter from a dream , is , in some sense , a private artist ; and the later work , as Varnedoe has organized it , suggests an increasing absorption in a personal vocabulary composed of body parts ; crosshatching patterns ( an overworked motif of the 1970s ) ; vases ; clocks ; skulls ; specific borrowings from Duchamp , Picassso , Holbein , and a 16 th -century Grenewald altarpiece ; little stick figures with bubble heads ; and , in the most recent work , the image of a spiral galaxy .
Grenewald was an artist in the 12th century .