翼龙的每个前肢都有一根长长的第四指，支撑着像翅膀一样的膜。

In pterosaurs a greatly elongated fourth finger of each forelimb supported a wing-like membrane.

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大部分的人在运用第四指时都有困难。

The 4th finger is particularly problematic for most people.

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然而拇指距离第四指和第五指多远才是最理想的呢？

However what is ideal for the thumb is way off for the fourth or fifth finger .

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