Ape Caged in Zoo (Symbol)
As the title of the play makes clear, the central symbol of the drama of Yank's life is that of the powerful and frightening ape who is nevertheless made into an impotent object of curiosity because of his imprisonment. As Yank tells the gorilla in the final scene, he feels caged by more than actual bars; it is his total alienation from society and his inability to realize his individualism in a meaningful way that makes him a prisoner, outsider, and eccentric curiosity in whichever situation he finds himself.
Mildred's White Dress (Symbol)
The white dress that Mildred wears into the stokehole may represent to her a certain daring, but as her boast to the second engineer that she has plenty of the same makes apparent, it is more so a sign of her upper-class disdain for the workers and feeling of distance from them. The visual force of this whiteness combined with the terrified look in her eyes constitutes the shock that Yank feels seeing them, a kind of insult that hits home.
Machine-like People (Motif)
From the way that the firemen snap to attention and file out of the forecastle at the sound of the bell to the insensitivity of the rich people on Fifth Avenue whom Yank tries to provoke, so many of the people depicted in the play are portrayed as bound to social forms to the extent that they have been robbed of their autonomy. Although they may seem to be human at times, in the right situation and with the right signal, they behave like Pavlovian dogs, responding with formulated motions to social signs.
Engineer's Whistle (Motif)
In Scene Two, the engineer's whistle is apparently an admonitory signal for the firemen to work harder. At the first whistle, Yank reacts with some contempt but feels motivated to shovel coal even faster. The second and succeeding whistles, however, infuriate him, since he feels himself to already be working much harder than any man could expect; he feels it as an insult to his power.
Membership in the I.W.W. (allegory)
After hearing about the radical labor activism of the I.W.W. while he is in prison, Yank goes to join them in Scene Seven. To his great chagrin, he learns that what he had hoped to be a “gang” he could belong to is in fact just as standardized and socialized a group as any other he has found before. Yank's conflict and ultimate (literal) ejection from the group allegorizes his being thrown out from any society, working-class association included.
