The Mishnah discusses a pit in a public area and all the related types of damage. If somebody puts his kash v'teven, different types of straw, in a public area in order for them to be processed into fertilizer, then when they are put on the ground and people step on them, they break down and turn into a certain type of fertilizer that's good for the ground. If a person slips on them and injures himself in a fall, the owner is obligated to pay for the injury, for the damage that he has caused. The first person to take them acquires them.
Here we're talking about a person who does not have permission to put his straw and his fertilizer out there in public. Therefore, he is obligated to pay for the damage that he has caused. The Hachamim (Sages) also said that even though he technically owns the straw that's out there, they wanted to penalize him for putting something in a public area when he wasn't allowed to do so. So they said that whoever wants to take it is allowed to take it. They uproot his ownership from it. We see from here that he's only obligated to pay for those damages if he was forbidden to put the straw in the Reshut HaRabim (public domain).
This seems to be contrary to the last Mishnah. In the last Mishnah, we said that even when a person has permission to put the water in the public domain, because it's the rainy season, he's still obligated. So we'll see that the previous Mishnah fits with the next opinion in our Mishnah, Rabban Shimon ben Gamliel, but he is going to disagree, obviously, with the Tanna Kama (first Tanna) that we have here. Gamliel omer—this rabbi says: “All different types of dangers that are put into a public area, even with permission.” For example, let's say it's the time of year that all the farmers are putting their fertilizer outside, and it's expected to be there. People always put it out during that month in order to convert it into fertilizer. Then they cause damage: the straw that was put outside over there caused injury to a person. The owner is obligated to pay. Anybody who grabs onto them, anybody who takes them, acquires them. We're talking about after the permitted period, when it was no longer allowed and that time had elapsed. Whoever took it is allowed to keep it. We're talking here about a situation where there was even permission for this farmer to put it outside. Rabban Shimon ben Gamliel says he's still obligated to pay for the damage, even though he was allowed to put it there in the first place.
Somebody is turning over fertilizer in the public area. Let's say he was trying to acquire it, and one means of acquiring it was grabbing onto it. So now he has taken ownership of it. Another person was injured by it. The person who took ownership is obligated to pay for those damages. Once he grabs onto it, even though he didn't put it in that spot, it becomes his responsibility. Therefore, if it caused damage, if it caused harm, it's on him, and he has to pay those damages.