Blood is the tissue that not only carries cells that transport oxygen, for example, the red blood cells, or fights infectious diseases, but it also carries messenger molecules, hormone-like factors that transport information from one cell to another, from one tissue to another, including the brain.
血液是一种组织， 它不只含有携带氧气的细胞， 比如说，红细胞， 或对抗感染性疾病的细胞， 它还含有信使分子， 这些类激素的因子， 能够在细胞之间传递信息， 还能在身体组织之间传递信息， 其中也包括大脑。