Each of these life - sustainng agents begins as a stem cell , a sort of hematological embryo.这三种维持生命的要素都起源于干细胞.干细胞是血液的胚胎.Dolly's legacy includes the possibility of making patient - specific embryonic stem cell lines...
Church bells tolled and black flags fluttered.教堂丧钟敲响,黑色的旗帜飘动。The rain pattered against the casements; the bells tolled for church with a melancholy sound.雨点噼噼啪啪地打在窗子上; 教堂里传来沉重的钟声,召唤人们去做礼拜.The church bell tolled the hour....