Since it isn't in the main text, I will post it here copied from the transcript:

My dearest Esther, – & all my dears to whom she communicates this doleful
ditty, will rejoice to hear that this resolution once taken, was firmly adhered to, in
defiance of a terror that surpasses all description, & the most torturing pain.
Yet – when the dreadful steel was plunged into the breast – cutting through veins –
arteries – flesh – nerves – I needed no injunctions not to restrain my cries.
I began a scream that lasted unintermittingly during the whole time of
the incision – & I almost marvel that it rings not in my Ears still! so
excruciating was the agony. When the wound was made, & the instrument
was withdrawn, the pain seemed undiminished, for the air that suddenly
rushed into those delicate parts felt like a mass of minute but sharp
& forked poniards, that were tearing the edges of the wound – but when
again I felt the instrument – describing a curve – cutting against the grain,
if I may so say, while the flesh resisted in a manner so forcible s to oppose & tire the hand of the operator, who was forced to change
from the right to the left – then, indeed, I thought I must have ex-
-pired. I attempted no more to open my Eyes, – they felt as if hermeti
-cally shut, & so firmly closed, that the Eyelids seemed indented into
the Cheeks. The instrument this second time withdrawn, I concluded the
operation over – Oh no! presently the terrible cutting was renewed –
& worse than ever, to separate the bottom, the foundation of this dread-
ful gland from the parts to which it adhered – Again all description would
be baffled – yet again all was not over, – Dr Larry rested but his own
hand, & – Oh Heaven! – I then felt the Knife rackling against the breast
bone – scraping it! – This performed, while I yet remained in utterly
speechless torture, I heard the Voice of Mr Larry, – (all others guarded a
dead silence) in a tone nearly tragic, desire everyone present to
pronounce if he thought the operation complete, or if any thing more
remained to be done; ˄ or if they he thought the operation complete. The general voice was Yes, – but the finger of
Mr Dubois – which I literally felt elevated over the wound, though
I saw nothing, & though he touched nothing, so indescribably sensitive
was the spot – pointed to some further requisition – & again began
the scraping! – and, after this, Dr Moreau thought he discerned a
peccant attom – and still, & still, M. Dubois demanded attom after
attom. – My dearest Esther, not for days, not for Weeks, but for
Months I could not speak of this terrible business without nearly
again going through it! I could not think of it with impu-
-nity! I was sick, I was disordered by a single question – even
now, 9 months after it is over, I have a head ache from going on
with the account! & this miserable account, which I began
3 Months ago, at least, I dare not read, nor revise, nor read,
the recollection is still so painful.

To conclude, the evil was so profound, the case so delicate, & the
precautions necessary for preventing a return so numerous, that the
operation, including the treatment and the dressing, lasted 20 minutes! a
time, for sufferings so acute, that was hardly supportable – However, I
bore it with all the courage I could exert, & never moved, nor stopt them,
nor resisted, nor remonstrated, nor spoke – except once or twice, during
the dressings, to say “Ah Messieurs! que je vous plains! –” for indeed I
was sensible to the feeling concern with which they all saw what I en-
-dured, though my speech was principally – very principally meant
for Dr Larry. Except this, I uttered not a syllable, save, when so often
they re-commenced, calling out “Avertissez moi, Messieurs! Avertissez
moi! –” Twice, I believe, I fainted; at least, I have two total
chasms in my memory of this transaction, that impede my tying
together what passed. When all was done, & they lifted me up
that I might be put to bed, my strength was so totally annihi-
-lated, that I was obliged to be carried, & could not even sustain
my hands & arms, which hung as if I had been lifeless; while
my face, as the Nurse has told me, was utterly colourless. This
removal made me open my Eyes – & I then saw my good Dr Larry,
pale nearly as myself, his face streaked with blood, & its expression
depicting grief, apprehension, & almost horrour.
When I was in bed, – my poor M. d’Arblay – who ought to write
you himself his own history of this Morning – was called to me – &
afterwards our Alex.