The ninth perek of Massekhet Sota, which began on yesterday’s daf, focuses on the case of an eglah arufah – a situation where a dead body is found between two cities and there is no indication as to which of the two cities was responsible for this individual. The Torah requires that the elders of the two cities appear in order to measure which of the cities is closer to the body; the elders of that city will bring a calf, which is killed, while the elders recite – in Hebrew – the statement that appears in the Torah, affirming that they played no role in the man’s death (see 21:1-9).
The Mishna on our daf discusses a situation where the measurements are to be taken, but the dead man’s head and body have been separated from one another. Rabbi Eliezer rules that we place the head near the body and measure from there; Rabbi Akiva rules that the body is moved next to the head. Similarly we find that with regard to the question of measuring in a normal case, Rabbi Eliezer believes that we measure from the dead man’s navel; Rabbi Akiva says that we measure from his nose.
The Gemara wants to suggest that the dispute between Rabbi Eliezer and Rabbi Akiva parallels another mahloket (argument) that is found in Massekhet Yoma (85a), where one tanna holds that an embryo develops from his head, while Abba Sha’ul believes that it develops from its navel. This suggestion is rejected by the Gemara, which argues that even if Abba Sha’ul believes that development begins at the navel, he may still agree that the life force of a living person is in his head.
On some level the dispute between the tanna kamma and Abba Sha’ul can be understood as a disagreement about where to place the emphasis in evaluating the center of the embryo’s development. On the one hand, the embryo’s head is the first part of the body that develops into a recognizable form, and only afterwards do the other limbs begin to develop. On the other hand, since the embryo’s development is sustained by the connection of the umbilical cord to the navel, one might suggest that it is from there that all development is seen as taking place.