疮疡为病，发见于外，外治药物尤为重要。凡轻浅之证，专恃外治，固可以收全功；而
危险大疡，尤必赖外治得宜，交互为用，此疡医之学。虽曰理法必本于治内，煎剂是其基础
，而薄贴、末子、洗涤等事，允为专门学术，非研究有素，阅历深而细心体会者，亦不能悟
彻此中神化也。
寿颐读古今治疡各书，外治诸法，亦既汗牛充栋，而按其实在之效力未可尽信。于此始
知徐洄溪谓治疡必有秘授之说为不虚。可知此公之于此道，自有家法渊源，独惜其所着之书
引而不发，不肯将此中秘旨宣布一二，以告后学，盖犹有吝惜之意，足见闭关时代习俗误人
。以此老之学识宏通，而尚有秘之一字在其胸中。
得毋所见犹小，然所学不传，亦颇为此老惜之。颐尝谓吾国医学，未必无出人意表之妙
，而向来奉为家秘不肯告人，因而辗转失传埋没不少。此道不扬，亦正坐此。然又尝谓所学
果精，方药果效，亦何必秘。凡深藏而不露者，即其学问不可告人之处。寿颐承师门之学，
经治验而来，未尝非世俗之所谓秘授，窃以为可以救人苦难，可以阐扬学识，民胞物与，即
在此中。请倾筐倒箧而出之，以与同志共为肄习。药不必贵而奇，惟在适用而有实效。是固
正直荡平之道，人人之所能知能行者。虽只寥寥无几，然已足以泛应而有余。果能神而明之
，化而裁之，窃谓向来各家秘钥，不肯示人者，或亦无以过此。
Sores and ulcers manifest externally, making external treatment medications particularly important. For mild and superficial conditions, relying solely on external treatments can indeed achieve complete recovery; however, for dangerous and severe sores and ulcers, appropriate external treatments are especially necessary to interact with internal treatments. This constitutes the study of Yu Yi (surgical medicine). Although it is said that principles and methods must be based on internal regulation, and decoctions form the foundation, applications such as plasters, powders, and washing procedures are specialized academic disciplines. Without thorough research, profound experience, and careful comprehension, one cannot fully grasp the subtle transformations within this field.
I, Shouyi, have read various ancient and modern books on treating sores and ulcers. The literature on external treatment methods is abundant (as numerous as to fill a cart and overload an ox), yet their actual efficacy cannot be entirely trusted. It is here that I understand why Xu Huixi stated that "treating sores and ulcers necessarily involves secret transmission" is not empty talk. This gentleman undoubtedly had his own family traditions and origins in this field. Unfortunately, his written works are reserved and do not reveal the core secrets, refusing to disclose even a few key points to guide future students. This hesitation reflects the misleading influence of customs during the closed-door era. Even with such broad and penetrating scholarship, he still harbored the concept of "secrecy" in his mind.
Could it be that his vision was limited? Nevertheless, it is regrettable that his knowledge was not passed down. I have often said that Chinese medicine may well possess extraordinary subtleties, but because they were traditionally kept as family secrets and not shared, much has been lost or buried through transmission errors. The failure to promote this path is precisely due to this reason. However, I also argue that if the learning is truly refined and the prescriptions truly effective, why keep them secret? What is deeply concealed and unmanifested indicates aspects of the learning that cannot be shared. I inherited my master's teachings, which came from clinical verification, and these were not unlike what the secular world calls "secret transmission." I privately believe that sharing this can save people from suffering and elucidate medical knowledge. The spirit of "treating all people as fellow citizens and all things as companions" lies within this act. Please open your chests and pour out everything, so that we may study together with like-minded individuals. Medicines need not be expensive or rare; they only need to be applicable and effective. This is indeed the way of integrity and openness, known and practicable by everyone. Although currently very few are revealed, it is already sufficient for broad application. If one can achieve divine clarity and flexible adaptation, I privately believe that the secret keys previously withheld by various schools would hardly surpass this approach.