How do the lines and stanzas of “a narrow fellow in the grass” contribute to the structure of the poem?

With the opening line of this stanza, the reader does not know who this narrow  fellow is, but because Dickinson describes him as a ‘fellow’ one can only assume  that this is a skinny man lying in the grass. She claims that he ‘occasionally  rides’ but implies that he spends most of his time in the grass. The speaker does  not go into detail about what the snake ‘rides’, but this description does give the  reader the impression that she is speaking about a thin human being. The  speaker claims that ‘his notice is sudden’ suggesting that one notices him  suddenly, and that he suddenly notices the presence of another. Then, when the  speaker describes this narrow fellow as one who ‘dives as with a comb’ and has  ‘a spotted shaft’, the reader becomes aware that the speaker is not referring to a  human being, but to a snake. With the first few lines, the speaker intended to  trick the reader into picturing a human being, so that it comes as a shock when  the reader realizes that this poem is about a snake. Then the speaker says that  the snake ‘closes at your feet’. The use of the word ‘your’ here, brings the reader into this experience. Now the reader can picture a snake at his own feet, and can  perhaps feel what the speaker herself has felt at this encounter with a snake. Once the snake has circled ‘your’ feet, he slithers away.

the right ones are in bold.

daintly refers to the fact she was reaching for what she ate, not necessarily what she is like.

greatest charm as in she possessed (=had) the greatest charm.

pleasant (her demeanor)

speaking (of her sensibility)

dead refers to the hypothetical mouse.

bleeding refers to the hypothetical mouse.