Because a rotating joint is essential to a wheel, a wheel made of living cells would twist its artery vein and nerve connections at the first revolution, making living impracticable.

• 因为一个旋转的接头对轮子来说是至关重要的,由活的细胞构成的轮子在第一次转动时便会扭伤其上的动脉和神经的连结,因而不现实。