Avot185

19:
In order to understand how the Romanophile Jews in the time of the Bar-Kokhba revolt could 'abrogate the covenant of Father Abraham' we must understand some of the anatomical details of circumcision. It is rather simplistic to think that all that is involved in circumcision is the removal of the foreskin. Non-ritual circumcision, as performed at the present time by medical practice, involves the removal of the whole sheath as far as the corona. Such an operation is irreversible. This has never been how Jewish ritual circumcision has been performed.

20:
In our classical sources the physical action which is involved in the 'abrogation of the covenant' is referred to as 'pulling the foreskin'. Indeed, in the Talmud of Eretz-Israel [Sanhedrin 49a] we are told quite specifically that "he who abrogates the covenant is one who pulls his foreskin" – and the context there is what amounts to an exposition of our present mishnah. Clearly, an abrogation of a covenant can only take place after the covenant has been concluded. But moderns will ask themselves how it is possible to restore what was removed during the brit milah by pulling a foreskin which is no longer existent.

21:
The covenant of circumcision [Brit Milah] involves the removal of the tip of the foreskin. What the mohel [ritual circumciser] actually does is to stretch the foreskin by pulling it forward over the glans and cutting off the projecting foreskin. According to our classical sources this was how the rite of circumcision was performed from the time of Abraham until the Torah was given at Mount Sinai: at Sinai an addition was made to the ceremony, the mitzvah of peri'ah, which will be explained shortly. However, the surmise of modern scholarship is that the addition of peri'ah was introduced either in the time of the Maccabees (2nd century BCE) or in the time of the Hadrianic persecution (2nd century CE); it was then projected back to Sinai in order to give it an aura of ancient authority.

22:
Underneath the foreskin is a mucous membrane. Mucous membranes line various body cavities that are exposed to the external environment and internal organs. Body cavities featuring mucous membrane include most of the respiratory tract, the entire gastrointestinal tract, including the rectum, the urethra, and various other organs. The inside of the foreskin is mucous membrane, not skin. If the mucous membrane is left intact during circumcision, in later years it can be 'pulled' forward. When this is done it might give the impression that circumcision had not taken place. The mitzvah of peri'ah – removing the mucous membrane together with the tip of the foreskin – would make it impossible to create a semblance of foreskin in later years. Thus the introduction of peri'ah had the practical effect, apparently, of making it impossible to 'abrogate the covenant of Father Abraham' by stretching residual mucous membrane.

To be continued.

Still in connection with Avot 179, Jacob Chinitz writes:

Rabenu Gershom’s Takana that a woman should actually say Rotza Ani before a Get is issued, raises the question: why do we not ask the bride whether she wants to be married to this man? Is it a matter of Shetikah Kehodaah? The Christian custom of asking both bride and groom, Do you take this person to be your lawful wedded spouse makes a lot of sense Halakhically, because even without R. Gershom, a woman cannot be married against her will. Why not ask her?

I respond:

We dealt with this issue at great length when we studied Tractate Kiddushin. (I apologise that the material is not yet available in the archives: I am at present preparing Tractate Berakhot for the archives; Kiddushin will come after that.) In brief: when a man proposes marriage to a woman this is done by offering her, in the presence of valid witnesses, an object of minimal value together with a declaration to the effect that by accepting this object (nowadays traditionally a ring) she signifies her willingness to be his wife. So the acceptance of the ring has the same practical significance as saying "I do".