Rhizoma Drynariae — Drynaria fortunei (Kunze) J. Sm., the dried rhizome of a fern (family Polypodiaceae); traditionally sand-scorched before use
Nature and flavour. Bitter, warm. Liver and Kidney systems.
The mildest item in this batch, and the one whose name is the most literal: 骨碎补 means mender of broken bone, and the classical description follows the name — quickening the blood and settling pain, supplementing the Kidney and strengthening bone. It is recorded for falls, blows and sprains, for injury to the sinews and bones, for lower back and knee weakness attributed to Kidney depletion in the traditional sense, and for tinnitus and loose teeth described the same way. The外用 record is the one that travels furthest: the herb is applied to the scalp in the traditional literature for patchy hair loss, and it is still a common ingredient in hair tonics sold today. That use is worth stating plainly and then setting down: the modern clinical evidence for it is limited and is not established, and hair loss has causes — thyroid disease, iron deficiency, alopecia areata, and others — that a topical application cannot address and that should be assessed rather than covered up.
性味归经。苦，温。归肝、肾经。
本批中性质最温和的一味，也是名字最直白的一味：骨碎补即「补碎骨」，古籍描述也照着这个名字走 —— 活血止痛、补肾强骨。记载用于跌扑闪挫、筋骨损伤、传统所论肾虚所致的腰膝痿软，以及同样归因于肾虚的耳鸣、齿松。传得最远的是外用记载：古籍以本品涂擦头皮治斑秃，至今仍是市售生发制品中的常见成分。这个用途值得照实写下，然后放下：其现代临床证据有限，尚未被证实；而脱发是有原因的 —— 甲状腺疾病、缺铁、斑秃等等 —— 外涂解决不了，应当去查明而不是遮掩。
八味中最温和的一味，仍然不是可自行使用的药材。它是活血药，故古籍孕期禁用；哺乳期同样慎用，因为这方面的证据根本不存在。传统以砂烫去鳞片毛须，那是作坊里按规范执行的一步，不该在厨房里临场发挥。蕨类材料受潮会发霉，发霉的一批应当弃掉而不是晒干了继续用。由于它是热门商品成分，流通中的掺伪与错标已有记载，已有数种槲蕨属植物及不相干的蕨类根茎以此名出现。斑秃、久不愈合的损伤或持续腰痛者，都应先查明原因，而不是当作某种虚损去补。任何使用都须在合格执业者监督下进行。