A short story about The Horse Chestnut

Speaking of the horse chestnut, I have also encountered it, in the early years every time I went to Germany to live, I would buy a European Rail Pass (starting at least three days), generally buy a half-day of the preparation of the residence, the more days to buy, the cheaper, the first-class car is almost few people to sit, with this European Rail Pass can take any train in the EU Schengen countries. Once with a friend to live in the town of Innsbruck for a few days, in the afternoon we couple wandered to a park, saw a big tree under the ground is full of shiny chestnuts, out of curiosity, I picked up a peeled shell and handed it to Mr. to let him taste what it tastes like, did not expect him to lick it, immediately spit desperately, the expression was painful, half a day can not speak, only a strong gargling with the mineral water I carried, I was frightened, asked him what is wrong? After a long time, he eased up and said to me, you almost became a murderer. Afterwards, he told me that at that time, his mouth was full of numbness, his throat was tightened, he seemed to be unable to breathe, let alone speak, and after some relief, he could not speak for a long time, and he really thought that he was going to become dumb. Later, friends who live in Germany told us that this is called horse chestnut, the raw material for external medicine, which is exactly the same as the edible chestnut, but it is larger and more beautiful than the chestnut, and the shell is bright, and the people who live in Europe and the locals know it. It's just that we lack common sense, haven't seen or heard of it.