Kommentar zu Tahorot 5:1
הַשֶּׁרֶץ וְהַצְּפַרְדֵּעַ בִּרְשׁוּת הָרַבִּים, וְכֵן כַּזַּיִת מִן הַמֵּת וְכַזַּיִת מִן הַנְּבֵלָה, וְעֶצֶם מִן הַמֵּת וְעֶצֶם מִן הַנְּבֵלָה, וְגוּשׁ מֵאֶרֶץ טְהוֹרָה וְגוּשׁ מִבֵּית הַפְּרָס, גּוּשׁ מֵאֶרֶץ טְהוֹרָה וְגוּשׁ מֵאֶרֶץ הָעַמִּים, שְׁנֵי שְׁבִילִין, אֶחָד טָמֵא וְאֶחָד טָהוֹר, הָלַךְ בְּאַחַד מֵהֶם וְאֵין יָדוּעַ בְּאֵיזֶה מֵהֶן הָלַךְ, הֶאֱהִיל עַל אַחַד מֵהֶם וְאֵין יָדוּעַ עַל אֵיזֶה מֵהֶן הֶאֱהִיל, הִסִּיט אֶת אַחַד מֵהֶם וְאֵין יָדוּעַ אֵיזֶה מֵהֶם הִסִּיט, רַבִּי עֲקִיבָא מְטַמֵּא, וַחֲכָמִים מְטַהֲרִים:
Ein Ungeziefer und ein Frosch im öffentlichen Bereich und in ähnlicher Weise das Volumen eines toten Körpers einer Olive und das Volumen eines Tierkadavers einer Olive oder ein Knochen eines toten Körpers und ein Knochen eines tierischen Kadavers oder eine Klumpen [Schmutz] aus einem reinen Land und einem Klumpen von einem gepflügten Friedhof, einem Klumpen aus einem reinen Land und einem Klumpen aus den Ländern der Nationen [dh außerhalb Israels] oder zwei Wegen, einer unrein und einer rein, wenn jemand einen von ihnen hinunterging und er weiß nicht, welchen er hinuntergegangen ist, oder [im Vorbeigehen] hat er einen von ihnen bedeckt [dh über das Volumen der Olive des toten Körpers oder des Tierkadavers] und er weiß nicht, welchen er bedeckt hat, oder er bewegte einen von ihnen [dh einen der beiden Knochen oder einen der beiden Schmutzklumpen] und er weiß nicht, welchen er bewegte, Rabbi Akiva erklärt ihn für unrein, aber die Weisen erklären ihn für rein.
Bartenura on Mishnah Tahorot
English Explanation of Mishnah Tahorot
And so also [if there was there] an olive's bulk of a corpse and an olive's bulk of carrion,
A bone of a corpse and a bone of carrion;
A clod of clean earth and a clod from a doubtful grave area
A clod of clean earth and a clod from the land of the Gentiles,
Or if there were two paths, the one unclean and the other clean, and a man walked through one of them but it is not known which,
Or if overshadowed one of them but it is not known which, or he shifted one of them but it is not known which:
Rabbi Akiva rules that he is unclean, But the sages rule that he is clean.
Today's mishnah brings up a series of cases in which one of two possible things occurred one which would have caused him to be impure and one in which he was not impure. In the end of the mishnah we can see that the rabbis and Rabbi Akiva disagree as to whether or not the person is pure or impure.
Section one: A dead sheretz causes impurity but a dead frog does not because it is not one of the defiling creepy crawly things listed in Leviticus 11:29.
Section two: Flesh from a corpse defiles in all ways, but flesh from carrion of an animal defiles only by touch and by carrying, not by overshadowing.
Section three: Bone of carrion is pure. Bone from a corpse defiles through contact and carrying.
Sections four and five: Earth from an area that might have been a graveyard defiles through contact and carrying, as does dirt from outside of the land of Israel.
Section seven: This section refers to all of the sections above.
Section eight: Rabbi Akiva says that doubtful cases of impurity in the public domain are pure only if the person didn't perform any action. But in the cases listed here the person moved, carried or overshadowed one of the objects that might have been impure, and therefore he is impure.
The other sages disagree doubtful cases of impurity are always pure in the public domain.