The Talmud goes on to say that even if the cumin had not been properly prepared (crushed or ground) before the Sabbath, one could grind it with his teeth on the Sabbath, an act which would generally be forbidden on the Sabbath - but is permitted, presumably on account of the role the herb/spice would play in stopping the blood and healing the wound.
עושין כל צרכי מילה [בשבת] מוהלין ופורעין ומוצצין ונותנין עליה איספלנית וכמון
On the Sabbath, we do everything that needs to be done for the circumcision: Remove the foreskin, remove the membrane from the glans, draw out blood, put on a bandage and cumin.
The differences in the reading open up a debate as to whether metzitzah, which I have defined as "drawing out blood" is considered to be: a. part of the steps of the process, or b. a suggested component that the Talmud records as the best known form of helping the wound heal.
If it is the former, then metzitzah must be done at every bris [how the blood is drawn is a topic of a different discussion, and of much debate, particularly in ultra-Orthodox and some Haredi/Hassidic circles]. If it is the latter, perhaps it need not be done,
because our understanding of science and medicine will demonstrate in very definite terms that drawing blood (certainly in the manner considered traditional) and putting on cumin are not the most effective ways of stopping bleeding. And if our #1 concern at a bris is for the baby, then we would do best to control the bleeding and care for the wound in the most effective way known to modern medicine under the circumstances of a public ceremony in which the bris usually takes place.
Is metzitzah an absolute necessity?
It is the opinion of Rav Pappa in the Talmud (Shabbat 133b) that not doing metzitzah is a cause to no longer use the mohel in question. [The Talmud says on Shabbat 137b that one who does not remove the membrane has effectively not circumcised. But there is no statement that suggests that if metzitzah were not done that the bris is unsatisfactory.] He argues that just as not bandaging is dangerous, not doing metzitzah (which was mentioned in the same breath as bandaging, ala our second way of reading the Talmudic passage) is also dangerous. Of course, with this argument, one could say that if contemporary medicine knows of no such danger, this "medical opinion" of the Talmud becomes obsolete.
Since Rav Pappa says a mohel who does not do metzitzah should not work again, I do believe it behooves every mohel to do metzitzah in a manner that is not even remotely harmful to the baby. I use the word "harmful" because putting a bacteria-laden mouth on the open wound of a newborn is not exactly a model example of normal wound-care practice according to medical science.
[Even the Shulchan Arukh is aware of the potentially harmful nature of bacteria in the mouth -
שולחן ערוך אורח סימן קע: סעיף טז: לא ישתה מהכוס (לז) ויתן לחבירו, מפני סכנת נפשות.משנה ברורה שם: (לז) ויתן לחבירו וכו' - שמא מחמת הבושה יקבל חבירו ממנו וישתה בע"כ ואולי חבירו מאיס ליה לשתות ממה ששייר זה דאפשר דנתערב רוקו שם ויחלה עי"זShulchan Arukh 170:16 - One should not drink from a cup and share it with his friend, on account of the potential danger to life
Mishneh Brurah there 37 - Perhaps on account of embarrassment (ie. social pressure) his friend will take it and drink against his will, and maybe he (the second guy) is disgusted by drinking what his friend left in the cup, because of the possibility that his saliva was left in the drink, and he'll become sick from this.
He goes on to add "that if he knows for sure that the person is healthy it need not be a problem." But we (modern man with medical knowledge) know bacteria in the mouth is not the best thing to be sharing. And while people certainly do it all the time in sharing drinks, that is a risk that adults take with one another. It is not a risk we can afford to take with newborns who have not yet developed an immune system. And infection we can get over with relative ease can be life-threatening to a newborn]
At the same time, we must bear in mind the words of Rabbi Moshe Feinstein, the most revered and respected posek/decisor of Jewish law of the latter half of the twentieth century. In his Responsa Iggeros Moshe, Yoreh Deah I:223, he wrote the following (translation follows)
שו"ת אגרות משה יורה דעה חלק א סימן רכג
ומה שנזכר בדברי כתר"ה חתוך פריעה ומציצה שהם ג' מעשים שאין אחד בלא חברו כלום כמצות ד' מינים. חושב אני שהוא רק פליטת הקולמוס שפשוט שמציצה אינו עכוב בהמצוה דהוא רק משום רפואה. ואולי כוונת כתר"ה להטפת דם ברית שהוא ודאי חלק מהמצוה. אבל לדינא מסופקני אם הוא עכוב כשיעשה חתוך ופריעה ולא יצא דם שיותר משמע שאינו שוב בדין ערל אף שהוא ג"כ עיקר בהמצוה. אבל אולי יצטרך אח"כ גם להטפת דם וצ"ע. ידידו, משה פיינשטיין
Regarding what the honored Rabbi wrote regarding the so called "3 stages" of a bris, that they are a unit and inconsequential if all three are not performed (as is the case for the four species that are waved during the holiday of Sukkos)... I think that is just a stroke of your pen writing [and not a valid statement] because it is obvious that metzitzah is not an essential element of the mitzvah, and that it is only for healing purposes. Maybe the honored rabbi was referring to the drawing of blood at a bris vis-a-vis hatafas dam bris, which is certainly a part of the mitzvah. I am still doubtful however if even that would render the bris invalid (were it not done) in a case where circumcision and removal of membrane were done normally and for some reason blood did not come out. Perhaps in that case, there would be a need for hatafas dam [but certainly not for metzitzah]