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我在讲“蜗牛”一课时,事前就找到几只蜗牛,在前一天装在盛满清水的玻璃瓶中,用水闷的方法迫使它们的头和腹足伸到壳外,以便在课堂上让学生观察。可是玻璃瓶太少,不能使学生人手一只,这样想叫每一学生当堂都能够观察,就没有充足的时间。于是我改用针刺的方法:用大头针从蜗牛螺旋壳中央的小孔上刺向壳顶,然后将大头针摇动几下,蜗牛的头和腹足就很快地伸出壳外。试验成功后,在上这一课的前一天,叫学生每人找一只蜗牛(我们这里蜗牛很多,儿童常玩它,容易找到)。课堂上每个学生发给他一块玻璃(学校安装玻璃窗剩下的碎玻璃),一个大头针,让学生把蜗牛放置在玻璃片上,用针刺之,很快蜗牛的头和腹足出现在玻璃片上。随后将大头针拔去,蜗牛就在玻璃片上缓缓行动。这样让学生进行观察,不但能看到它的两对触角和呼吸孔,并且拿起玻璃片
When I was teaching “Snail”, I found a few snails in advance and packed them in glass bottles filled with clear water one day before, and forced them to stretch their head and belly out of the shell with the help of water, in order to make Student observation. However, too few bottles, can not make a student hand, so want to call each student when the church can observe, there is not enough time. So I use the method of acupuncture: a pin from the snail screw shell pinhole to the top of the shell, and then shake the pin a few times, the snail’s head and belly feet quickly out of the shell. After the test is successful, ask the students to find a snail for each person (we have a lot of snails here, children often play with it, easy to find) on the day before this lesson. Each student in the class sent him a piece of glass (the rest of the school-mounted window glass), a pin that allowed the student to place the snail on the glass and acupuncture, and soon the snail’s head and gastropod appeared in the glass Chip. Then unplug the pin, the snail slowly act on the glass. This allows students to observe, not only to see its two pairs of antennae and breathing holes, and pick up the glass