This line can be read in a few different ways. On the one hand, the speaker might be suggesting that he has never encountered a snake, whether accompanied by others or alone, that has not caused extreme anxiety. On the other hand, though snakes usually travel alone, some snakes, particularly rattlesnakes, are often spotted together around mating seasons. The sight of one snake alone is terrifying enough to send the speaker into “tighter breathing,” let alone two.

By “Several of Nature’s People,” the speaker is referring to animals. In other words, the speaker feels an affinity for all animals, except the snake. Because of the phallic shape of the snake, many literary critics have purported that the speaker’s fear of the snake is a symbol for Dickinson’s sexual fears. However, this is open to interpretation.

Dickinson’s handling of end rhyme is elliptical and subtle. As the poem progresses, there are more and more instances of end rhyme, most notably between the second and fourth lines of each stanza: “seen”/“on”; “acre”/“corn”/“noon”; “me”/“cordiality”; and finally the satisfying resolution of “alone”/“Bone.”

Notice that we are given a description of our speaker for the first time here. The word “Boy” tells us that the speaker is male and describing an experience he had in his youth. The fact that the speaker is both young and “Barefoot” also underscores the speaker’s innocence and vulnerability. Dickinson thus makes the encounter with the snake seem more frightening and sinister. The imagery of a snake slithering across a “Barefoot” is particularly distressing and unsettling.

The final line contains a multi-layered metaphor. The phrase “Zero at the Bone” describes bone-chilling horror, a zero-degree temperature. It also suggests a state of personal annihilation, of becoming nothing. This final quatrain shows that the snake, personified as a harmless, “narrow Fellow” in the first quatrain, is not a person at all but a threat. The speaker, who loves all creatures, cannot love the treacherous trickster, the snake in the grass, the serpent in the Garden of Eden. Most pressingly, the speaker’s metaphors for the snake fall away, revealing the terrifying reality of the creature. This shift from trust to cold distrust is the poem’s central thematic turn.

Notice the imagery of the grass covering up the snake so that the speaker only sees flashes of the snake. The snake is almost invisible and ghostly, moving underfoot in near secrecy though his presence is palpable for the speaker. This movement is untraceable, meaning that his appearances are even more shocking. Dickinson’s imagery here thus makes the snake seem even more sly and menacing.

Em dashes are used to indicate an abrupt change in thought. Though Dickinson often used em dashes for various, irregular reasons, the em dash here is critical. Since the speaker is trying to convey the “notice sudden,” or the surprise, that the sight of a snake often causes, the em dash gives the line the same jolting feeling that one would experience when encountering a snake in real life.

The word “transport” operates in two ways here. A “transport” can refer to an emotionally charged trance or rapture. In this case, the speaker experiences an overwhelming feeling of “cordiality,” or good will, towards “Nature’s People.” By a more obscure definition, “transport” is a synonym for metaphor. Thus the speaker admits that the cordiality she feels for “Nature’s People” is an act of projection. Indeed, the personification underlying such a phrase is a marked example of metaphor. The poem’s great thematic shift is a move away from a metaphor-driven relationship with the natural world.

The speaker directly addresses the reader here, and the dialogue seems formal, but nonchalant. The use of the verb “met” is also casual, making an encounter with a snake seem unalarming, normal, and even cordial. Note too, that the snake is personified again with intentional capitalization of “Him,” giving the snake a less menacing, more human presence.

Notice that Dickinson uses the verb “rides” to describe the snake’s movement. The word sounds similar to “glides” or “writhes,” which one might usually associate with snakes. However “rides” suggests that the snake is being carried or floating along, making the snake seem less threatening and more passive. Note however, that the verb “rides” can also mean “to torment, harass, or tease,” which alludes to the snake’s sly nature. This clever word choice on the surface contributes to the jovial tone of the poem, while alluding to the snake’s hidden cunning.

Notice that the word “Fellow” is capitalized. Dickinson often capitalized various words in her poems for emphasis. It is unclear why Dickinson chose to capitalize “Fellow,” but it could be speculated that since the snake is personified as a “narrow Fellow,” the capitalization might be acting as it would for a proper noun, further personifying the snake.

The metaphor of the “Whip lash/ Unbraiding in the sun” is clever in the context of the poem’s broader themes. Throughout the poem, the speaker attempts to make sense of the snake by personification and comparison. As the poem reaches its conclusion, those attempts at familiarization fall apart. Thus, the figure of the whip lash begins unbraiding as soon as it appears.

An internal rhyme is a rhyme created by two or more words in the same line of verse. “narrow Fellow” is an example of an internal rhyme because of the repetition of the “ow” sound at the end of both words. The two words also create what is called a “slant rhyme,” which is a rhyme that forms similar, but not identical, sounds. In this case the slant rhyme is formed by the “rr” and “ll” consonant sounds in the respective words.

In the opening line, Dickinson cleverly disguises the subject of the poem, a snake. “Narrow” means small in width, and “fellow” is a familiar term for a man or a boy. Using colloquial language like “narrow Fellow” makes the snake seem must less sinister and gives the poem a lighter, more amiable tone that contrasts with the poem’s tense subject matter.

This line serves as an excellent illustration of Dickinson’s subtle control of rhyme, assonance, and consonance. Most of the consonants in the line—f, c, and the liquids r and l—are repeated, often several times over. The assonance is equally pronounced: “Floor,” “for,” and “corn” all share vowel sound rhymes, as do “too” and “cool.” These musical flourishes do not necessarily figure in the poem’s thematic meaning, but they contribute greatly to the poem’s lyrical power.

The third stanza opens with a quickening of the meter. The alternating tetrameter and trimeter of the first two stanzas tightens up to a strict trimeter pattern as the poem hastens to its close. It is almost as if the snake were approaching more rapidly.

The image of the comb continues the poem’s titular metaphor: the snake as a “fellow.” Dickinson engages in this type of personification throughout the poem, adding additional touches to the snake’s identity as a person. These instances of personification build up to the final thematic turn, which reveals how non-human the snake truly is.

Another example of Dickinson's technique is rather than using the usual descriptors for a snake's motion, Dickinson again creates a concrete image: she shows a a harmless "whiplash" which, instead of slithering or writhing, merely "wrinkles."

Dickinson's many personae here include a man recalling boyhood.

Despite the fact that Dickinson welcomes nature into her life, here she exhibits an instinctively negative reaction to the snake—her blood runs cold. Dickinson, raised in the Puritan faith which she later rejected, could not help but see the snake as a symbol of evil.

This stanza illustrates the closeness Dickinson feels for nature in general, an important theme in her poetry that brings her into the circle of the Transcendentalists, who believed that Nature is, if not equal to God, almost as important as God.

One of the hallmarks of Emily Dickinson's poetry is to draw unusual comparisons.  In this case, Dickinson doesn't say the snake crawls through the grass; her image is much more concrete and visual—the snake moves through grass like a comb through hair.

Rather than use the word snake, which may have negative connotations for the reader,  Dickinson constructs a completely non-threatening image.  As readers, we might react with horror to snake but we are probably comfortable with a narrow Fellow.