请问怎么理解〈无形人〉中，每个农场主的推荐信里只有“KEEP THIS NIGGER-BOY RUNNING”这个现象？

“KEEP THIS NIGGER-BOY RUNNING”其实是反映了美国黑人作品中的The Running Theme. 分析如下：
　　the narrator’s dream also introduces the theme of the running man, alluded to in the phrase, “Keep this Nigger-Boy Running.” The running-man theme is a major motif in African American literature, tracing its roots to the slave narrative. But unlike enslaved Africans, often forced to run for their lives, the narrator starts running and is kept running by others who seem to have little real impact on his life. The narrator is on the run throughout the novel.

　　关于美国黑人的这种“逃跑”主题，下面也有一首诗，可供分析：

　　"Run Nigger Run" - an African-American Folk Song

　　Do, please, marster don't ketch me,
　　Ketch dat nigger behin' dat tree;
　　He stole money en I stole none,
　　Put him in the calaboose des for fun!

　　Chorus:
　　Oh, run, nigger, run! de patter-roller ketch you.
　　Run, nigger, run! hit's almos' day!
　　Oh, run, nigger, run! de pa