Dryopteridis Crassirhizomatis Rhizoma (Dryopteris crassirhizoma Nakai — dried rhizome with the leaf-base remains)
Nature and flavour. Bitter, slightly cold; counted as slightly toxic. Liver and Stomach systems.
The dried rhizome of the thick-stemmed wood fern, still bearing the brown leaf bases. It does two different jobs in the materia medica: it is grouped with the anthelmintics for killing parasites — roundworm, tapeworm and hookworm — and separately it is used to clear heat and resolve toxin, and charred to stop bleeding. That split is why it appears in more than one classical category. It is one of the most thoroughly documented of the toxic herbs here: the phloroglucinol compounds it contains are the same group found in the European male fern, and poisoning has been reported. The traditional indications are recorded rather than established.
性味归经。苦，微寒；有小毒。归肝、胃经。
用药部位是粗茎鳞毛蕨的干燥根茎，连同残留的棕色叶柄基部。它在本草中承担两类不同工作：一是归入驱虫药杀虫（蛔虫、绦虫、钩虫），二是单独用于清热解毒，炒炭后用于止血 —— 正因如此，它在古籍中见于不止一个分类。它是本批中中毒记载最明确的一味：所含间苯三酚类成分与欧洲鳞毛蕨同属一类，曾有中毒报告。所载用途属传统记载，未被证实。
文献列为有小毒，且这一味确实当得起这个标注：所含间苯三酚类成分与欧洲鳞毛蕨同类，曾有累及胃肠道与神经系统的中毒报告，其中包括视觉异常。本品在任何理解下都不作自用。孕期与哺乳期禁用，儿童避免使用；脾胃虚寒者及肝、肾疾病患者不宜。历来有多个物种曾以此名流通，品种鉴定关系重大 —— 非正规渠道所获药材没有常规质量控制。传统的止血用途涵盖子宫出血，而出血在用药之前必须先明确诊断。
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