This is the text from the Folio, with spelling, punctuation and capitalization amended.

Thus do I ever make my fool my purse:

For I mine own gain'd knowledge should prophane

If I would time expend with such snipe

But for my sport and profit: I hate the Moor,

And it is thought abroad that 'twixt my sheets

She ha's done my Office. I know not if't be true,

But I for mere suspicion in that kind

Will do as if for surety. He holds me well,

The better shall my purpose work on him:

Cassio's a proper man: let me see now,

To get his place and to plume up my will

In double knavery. How? How? Let's see.

After some time, to abuse Othello's ears

That he is too familiar with his wife:

He hath a person and a smooth dispose

To be suspected: fram'd to make women false.

The Moor is of a free and open nature

That thinks men honest that but seem to be so,

And will as tenderly be lead by'th'nose as asses are:

I hav't: it is engend'red: hell and night

Must bring this monstrous birth to the world's light.

While we have amended the Folio text, there are still some choices we have to make to get the text useable for performance.

The verse starts off fine: those first two lines fit the pattern easily, but then that third line...

If I would time expend with such snipe,

There's a beat missing, just 9 beats instead of 10.  Knowing printers aren't infallible, especially if they are typesetting scripts that were handwritten, it looks like they missed a word:

If I would time expend with such snipe,

Now the line fits the pattern.  This is how modern editors have printed the text.

The next "odd" line is the next line, and here Chicspeare opts for a printing of the text that does not conform to most editions for readers, which is set as

But for my sport and profit: I hate the Moor,

As printed we have eleven beats, and it sounds weird to have "the" stressed and "Moor" unstressed.

But if one pronounces "profit" as "prof't" (the sort of contraction that will be used elsewhere in the speech), the rhythm plays out in the pattern, and "the Moor" is a standard iamb. 1

But for my sport and prof't: I hate the Moor,

The next line that doesn't fit iambic pentameter is the 12 beat line

She ha's done my Office. I know not if 't be true,

It starts with an obvious misprint. Iago is referring to Othello and he is no "She"; the pronoun should be "He".

But is the error just the wrong pronoun or was the type supposed to be set as "He's"? And that space between "if" and "'t" is odd. Should it be said "if't" or "if it"?

Here are possible ways the line might be read:

He's done my office. I know not if't be true, 11

He has done my office. I know not if't be true. 12

He's done my office. I know not if it be true. 12

He has done my office. I know not if it be true. 13

For now, it seems that the line works best as a 12 beat line, but which choice we'll leave for now; the answer may become clearer when we analyze other layers in the speech's construction, particularly repetition of sound.

The next line with a rhythm variation also has 12 beats.

Will do as if for surety. He holds me well,

There is an expansiveness with these 12 beat lines, which will become important later as we look at the way thoughts come upon one another, as indicated by the punctuation.

Iago settles into an even rhythm for the next four lines until the line

After some time, to abuse Othello's ears

If we contract "to abuse" to "t'abuse", we get an iambic pentameter line.

The next line with an odd rhythm is

To be suspected: fram'd to make women false.

It can be solved with the same sort of contraction:

To be suspected: fram'd to make wom'n false.

The next line can't be solved so easily.

The Moor is of a free and open nature

Maybe you can figure out a way to get that line to conform to iambic pentameter. All we could come up with was to contract "Moor's". That puts stresses on the words "a" and "and" which work, but has you stressing syllables in "open" and "nature" in a way that does not conform to standard pronunciation.

So, it seems we have an 11 beat line. There are times characters speak 11 beat lines; it is as if the character has more to say than time to say it (which we may want to think about as we keep working out Iago's state of mind during this speech). 2

If we keep this line at 11 beats, we have two options. We can keep the extra energy in the line, and end with two stressed syllables:

- / - / - / - / - / /

The Moor is of a free and open nature

Or we can carry the extra energy into the next line, and stress the first syllable "that" as well as the normally stressed second syllable "thinks"

- / - / - / - / - / -

The Moor is of a free and open nature

/ / - / - / - / - / -

That thinks men honest that but seem to be so,

Both choices are valid; the actor decides which works best, depending on what resonates best with the Iago he is discovering.

Whichever decision is made, however, following line is 11 beats, with an awkward rhythm at the end. But if you contract "honest" to "hon'st" (like we did profit/prof't and women/wom'n), the line works in iambic pentameter.

- / - / - / - / - /

That thinks men hon'st that but seem to be so. 3

We have come to the last line in the speech which is not in iambic pentameter:

As asses are:

With only 4 beats it's short some iambs. Short lines usually are shared with another character, but Iago is alone on stage; there is no one to complete the line. Short lines can also indicate a pause, but that doesn't seem to work here. Iago has figured out what to do, and the next two lines are a rhyming couplet, a familiar device to note the end of a scene and movement into the next. To pause here doesn't match the energy of Iago's thought and action.

We decided is combine this line with the line before, for a 14 beat line.

Talk about expansive energy! Iago is full of purpose and intention as he heads off stage --

And will as tenderly be lead by'th'nose as asses are:

I have't. It is engend'red. Hell and night

Must bring this monstrous birth to the world's light.

1 Editors that keep the spelling of "profit" allow for a stress on "I"; they may have decided that stress is useful in understanding Iago.

2 That may be another reason editors leave "But for my sport and profit: I hate the Moor" as an 11 beat line: Iago has too much emotional energy to be contained within the regular rhythm pattern.

3 which creates a line of one-syllable words -- which are something else that can be used effectively to find the energy in a character's thoughts.  More on that later....