The scrapie agent in sheep may be similar to viroids. 綿羊的搔癢病因子可能也是類(lèi)病毒。
Statistics on occupational mortality have been of greater value in these respects than in initiating the study of new aetiological agents. 不同職業(yè)的死亡率的統計對這些方面的價(jià)值較之對于開(kāi)展新的病因研究的價(jià)值更大。