"…Even if it was explicit in the Talmud [and it is not] that the suction is meant to be oral, nevertheless since this is not an integral part of the circumcision, but only adjoined because of a health measure, so if one circumcised and did not suction the blood, he has already performed the commandment, and the baby is permitted to eat terumah, and the father may make a Passover sacrifice.…"
On The Main Line has translated the full exchange between the Hatam Sofer and his student, Rabbi Elazar Halevi Segal Horowitz, Chief Rabbi of Vienna, about metziztah b'peh (MBP), the direct oral to genital sucking done to the baby's open circumcision wound by the mohel. Horowitz asked Sofer if MBP should be stopped in light of the new medical opposition to it caused by infant deaths:
…Teach me, Rabbi, what is the rule regarding a question which my local friend Dr. Wertheim asked of me. According to the law of our religion is a mohel required to make that suction which is performed after the circumcision specifically with his mouth? Or perhaps it is proper to peform the suction through some other means, such as to soak a sponge in wine or water and squeeze the place of the wound with it a number of times, and through this achieve the healing effect for the infant no differently than through oral suctioning? The circumstances behind this question is that some months ago in our city many children who were circumcized by a certain expert mohel developed festering sores all over the genitals and from there it spread to the entire body. Many infants died because of this, and were unresponsive to any medical attention. Some of them lived, but were in great pain. The doctors judged that this condition was caused by the mohel's orally suctioning the wound (ha-metzitzah she-be-feh). The mohel was examined and proved to have a clean bill of health, and they could not diagnose anything like this illness in him. However, we need to know what to do in a situation like this in general.…
Horowitz goes on to make several points and conclude that he believes MBP should be banned.
Here is the Hatam Sofer's response in full (you can read all of Horowitz's reasoning over at On The Main Line):
Sheviti, etc. Pressburg, Monday, 20 Shevat 5597 (1837)Greetings and long life to my student and friend Rabbi Elazar Halevi Segal Horowitz, Chief Rabbi of Vienna.Your nice letter reached me, and it is correct what you wrote, that we do not find the metzitzah (suction) is specifically with the mouth, save for the position of the Kabbalists who say that [the process] enacts a neutralization of strict judgment through the lips and the mouth. We are not engaged in mysteries when there is some concern for physical danger. Now, the roots mitz and matzat are the same, c.f., Proverbs 30[:31] mitz apayim and Judges 6:38 "and wrung dew out of the fleece." In all these places Rashi explains them in terms of squeezing, compressing, and suctioning something with force. Radak and Ibn Ezra similarly explain them. If so, we only need to draw the blood from the 'far places' though whichever method we are able, and we can rely on experts who assure us that some method accomplishes it. I further say that even if it was explicit in the Talmud that the suction is meant to be oral, nevertheless since this is not an integral part of the circumcision, but only adjoined because of a health measure, so if one circumcised and did not suction the blood, he has already performed the commandment, and the baby is permitted to eat terumah, and the father may make a Passover sacrifice. However he is in physical danger so long as the blood was not suctioned from the far places. In Chapter Rabbi Eliezer De-mila we find that Rav Pappa understood that suction is similar to the dressing and cumin, which are health measures. Now, we do not presently use the [particular] dressing [specified in the Talmud] and cumin, nor the particular type of dressing mentioned in the Talmud by Abbaye and Rava. Therefore we know that since these are for healing, we are not particular about which remedy we use in its place, and the same thing applies to suction - even if oral suction had been mentioned in the Mishnah, we would be able to change it to another method which accomplishes the same thing, so long as we heed qualifies physicians who will attest that in truth a sponge accomplishes the same thing as oral suction. More than this we needn't be concerned with, in my opinion. God should heal you and make you feel good!Moshe ha-kattan Sofer mi-Frankfurt di-Main