In the most basic sense, "Spine" is a depressing work-a-day anthem. Consider the tiring, monotonous, doleful tone and lyrics ("I been draggin' my feet...") that characterize the song. The imagery portrays someone after a long day of work: he "drags" his feet, lets fall his weary head back against his neck, and rubs his temple ("walkin' my fingers through my mind").
The first three lines characterize someone without a spine at all--the person might be collapsed forward, such that his back falls upon his feet and his head falls back onto his unsustained torso. The implication is that the narrator's literal spine has failed him, and that he has had to endure the day without the physical support a backbone would provide. Instead of being helped by his spine, the narrator "feels a feelin'" in it, an indication of pain.
The closing indicates that once the narrator no longer has to work ("when I don't need a spine"), he'll get rid of it. In more realistic terms, the spine itself may be a metaphor for manual labor: once he doesn't need to work anymore, he'll get rid of his backbreaking, undependable(e.g. low-paying) job.
Consider also that "Spine" leads into "Memo to Human Resources," a song that also carries a strong aversion-to-work overtone.
Like "my man" on Mink Car the narrator of this song seems to what to disconnect from his body. (Mr Tuck)
The song is clearly from the point of view of a spine. (What human could drag his feet across his back? Only a spine can, since it's literally across the back and drags the feet. And even someone super-flexible couldn't walk their fingers thru their mind, but since a spine connects to the brainstem, it can.) The spine naturally assumes the rest of the body is his (my back, my feet, my neck) and so is upset at the commands from the brain which run down his spine and so he plans to leave those behind when he's in power and doesn't need that spine!
It could also be about a dendritic spine which is controlling the rest of the body (dragging the feet across the back) and plans to get rid of the other, actual spine, of whom he is jealous. 
It might still be about a human. This human has super powers, or is a contortionist. He enjoys twisting his body around, but his spine is restricting him. He'd rather just not have a spine at all.
Or... a guy's back hurts, and he'd rather leave the pain behind with the problem, being his spine.
[The first part talks about how he's been wearing out his back (walking a lot and stuff) and hows it's been bugging him (he does the whole roll your head back thing). He thinks about it (walking his fingers through his mind) and he remarks something like, "I can't wait till I'm rid of this thing!" because it's been bothering him. The end.] ~ magbatz
The above interpretation seemed kind of simple to me, considering the first couple lines, but then I worked through them:
"I've been draggin' my feet across my back"
Who does that? Crickets. They're chirping.
"And I've been rubbin' my head against my neck"
When I tried to do this I noticed that at any degree it would look like I was sleeping in my chair. Also, the pillow may push your head up against your neck.
"And I've been walkin' my fingers through my mind"
Before you go to sleep you may do this. Or if you think dreaming is recalling memories you could already be asleep.
"And I've been feelin' this feelin' in my spine / And I believe I'll be leavin' it behind / When I don't need a spine."
The above interpretation comes in. This guy has trouble with his back related to his bed and how uncomfortable it is. The important part is where he is pointing the blame - at his spine, and not the bed.
I think the phase When I don't need a spine refers to when the narrator dies. The spine is one of the most important parts of the body, and without it, we'd die.
The narrator is coming apart at the seams. He's crushed, spiritually and mentally. Quite the opposite of the preceeding Experimental Film. That's what makes The Spine so interesting, it has this constant dual theme of limitless ambition and sucess, and crushed, broken dreams and failure. If you look at the album like a story, as some seem to like doing, we can guess that the expiremental film isn't turning out that great. The narrator is "running his fingers through his mind," similar to how someone might finger through files in a filing cabinet or something. He wants to know where he went wrong. To put it in the terms of Memo, he wants to know where he lost the plot. He decides that he doesn't need his spine problems, or the rest of his problems, and is just going to leave them behind when he doesn't need them, or in otherwords, like sheep said, when he's dead. He's considering suicide to get away from all of his pain. Anyone who goes on to listen to Memo learns that he can't go through with it.
Ecstacy. It destroys your spine, and the rest of the song describes it.
Incidentally, did anyone else notice how perfectly this song leads into Memo to Human Resources? I for one didn't realise they were separate songs when I first listened to the album.
I second that motion anonny had mentioned. --Lemita 19:39, 5 Jun 2006 (CDT)
- The line "I'll be in the back" gains a new meaning.
Personally, I think that TMBG uses spines as a symbol for life, and, to greater extent, physical experience. The singer, after describing the painful contortions of his life, concludes that life is not worth living.
I think the spine is a metaphor for trying to be tough, and the narrator is saying that he's done with trying to be invulnerable and bulletproof, that he doesn't need his spine anymore.
I'm seconding Magbatz on this one. Linnell's known to have a terrible bad back, and I have a bad back as well. I've longed for not needing a spine MANY times. I'm sure that Linnell's done that too. - Rev. Syung Myung Me (talk) 21:13, 5 April 2014 (EDT)
I interpreted it based on the expression to "have (or not have) a spine", which means to be diligent and perseverant, or to be of strong fortitude in character or emotions. The speaker describes the cartoonish image of himself walking without a spine and bending over backwards (figuratively and literally) as his feet meet his back and his head falls back to reach his own neck, and he remarks how he's been 'walking [my] fingers through' his mind, fingering through and mulling over a thought that he was prompted to consider from a gut feeling (or in this case a 'spinal feeling', as he puts it; although this could also be read as him being prompted from the soreness of his emotional spine due to over-use for the sake of pleasing or appealing to others), and he concludes with the idea itself and his affirmation of it: "I believe I'll be leaving it behind when I don't need the spine." In other words, he intends to stop constantly being something that other people want him to be; he decides that, whenever being professional, perfect, and superlative isn't needed, he'll opt to remain "spineless" as others may describe him, damn the consequences. —Preceding unsigned comment added by 184.108.40.206 (talk) 16:31, July 2, 2014
The image I always get when I hear this song is that of a person going through some kind of transformation (or desiring to at least) into a mollusk, insect, or some other invertebrate. I've never seen Crispin Glover's film "What Is It?", so I don't have a context for this line, but in the trailer, a voiceover muses, "Four hundred snails. Four hundrd more injections. Free of this human form. Free of this opposable thumb." That line, and that idea of a willing transformation into something inhuman, came to mind when I heard the closing phrase "when I don't need a spine."
Part 2 of The Spine
The film opens to a truck driving on a country road (as seen in the liner notes). The Skullivan thinks about where he's gotten in life so far, while the credits are rolling. He thinks about how he will be free when he doesn't have the Spine anymore, which introduces the next character, The Spine.
Singers: The Skullivan