In Europe, where very few people brushed their teeth, it was found that wild boar hairs were too stiff and made the gums bleed, so horse hair, which was softer, was used instead.
在欧洲，很少人刷牙，人们发现野猪毛太硬，会使牙龈流血，而马毛更柔和些，于是就改用了马毛。
2
Sudden movements or noise can frighten a horse. A horse defends himself with strong teeth, sharp hoofs, and speed for running away from danger.
突然的动作或噪音会使马受到惊吓。马使用坚固的牙齿、尖锐的马蹄和迅速逃离危险的速度，进行自卫。
3
The horse may become obsessed with chewing any wood they can get their teeth into.