A simple way is to stick a clean finger in your mouth and scrape saliva from the back of your tongue. Put it on the back of your hand, wait a minute, then smell your hand.

一种简单的方法是放一根干净的手指到你的口腔里，再到舌头的背面去刮一点唾液，然后涂到手背上，一分钟后再闻一闻。

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The coarse bristles of my hand broom were going to scrape their sandaled feet, but even when I stood directly in front of them saying "Excuse me" over and over, they didn't see or hear me.

WSJ: Life Among the 'Garbage Faeries' : Inside the Sanitation Department