You may have met him? Did you not
His notice instant is -
Here, the speaker is implying the ubiquity of the "narrow fellow," without naming him explicitly as the snake. By highlighting the snake's "notice instant," the speaker is hinting at its capacity to appear and vanish in a brief moment. At this early point in the text, the speaker is still being relatively coy about who and what the "narrow fellow" really is.
But when a Boy and Barefoot
I more than once at Noon
In these lines the speaker of the poem is revealed to be a man, remembering a moment from childhood. The mention of bare feet is significant as it places the speaker in more peril from the narrow fellow. The combination of these two descriptions paints an image of the speaker doubly vulnerable in these early encounters with the snake. This element makes his curiosity all the more dangerous in the eyes of the reader.
But never met this Fellow
Attended or alone
Without a tighter Breathing
And Zero at the Bone.
These final lines nicely encapsulate the overall mood of the poem. The speaker frames his encounter with the snake as instilling both wonder and fear. He describes his "tighter Breathing" and "Zero at the Bone" (chills) during every meeting he has with the snake. In referring to these specific feelings, he is revealing the way in which his admiration for the snake is intractable from his fright.
