The digestive canal represents a tube passing through the entire organism and communicating with the external world, i.e. as it were the external surface of the body, but turned inwards and thus hidden in the organism.
消化道是一根管子，它穿过整个有机体，与外部世界沟通，也就是说，它是身体的外部表面，但向内翻转，因此隐藏在有机体中。
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