Blood sacrifices (xueji 血祭, xuesi 血祀, xueshi 血食) were sacrificial rituals during which animals were slaughtered and their blood offered to deities or spirits. The ritual Classic Zhouli 周禮 (ch. Da zongbo 大宗伯) explains that blood was poured out during the offerings to the soil and grain spirits (sheji 社稷), the Five Offerings (wusi 五祀), and the offerings to the Five Sacred Mountains (wuyue 五嶽).
The Later-Han-period 後漢 (25-220 CE) commentator Zheng Xuan 鄭玄 (127-200) remarks that these types of sacrifices were "dark" Yin sacrifices (yinsi 陰祀) during which the odour and "energy" (qi 氣) of blood was held in high esteem. A similar interpretation was given by the Song-period 宋 (960-1279) scholar Chen Hao 陳澔 (1260-1341), author of the commentary collection Liji jishuo 禮記集說. He explains that blood was seen as the carrier of vital qi.
The chapter Jiaotesheng 郊特牲 in the ritual Classic Liji 禮記 says that lung, liver, and heart were the main carriers of qi.