‘Hua Tuo’s Unofficial Biography’ relates: There was a woman from Langya who developed a sore on her right thigh, which tickled but didn’t hurt, recovering but then growing further. Tuo said: “One ought to obtain a dog the colour of rice husk and drag it with horses, exchanging when wearied, for fifty li; decapitate it and smear the blood on the itchy spot, which will then [improve].” This advice was followed. Immediately a snake was seen moving in her skin; placing an iron needle along its length they drew it out – it was perhaps three feet long – and seven days later she had quite recovered.
Anon., Jin Xin 金心 (ed.), Huhai xinwen yijian xuzhi 湖海新聞夷堅續志, 2.228 (Tale 408):
Yuan Haowen 元好問, Chang Zhenguo 常振國 (ed), Xu Yijian zhi 續夷堅志 (Continued Records of the Listener), and Anon., Jin Xin 金心 (ed.), Huhai xinwen yijian xuzhi 湖海新聞夷堅續志 (Continuation of Records of the Listener with New Items from the Lakes and Seas) (Beijing: Zhonghua shuju, 1986).
A much earlier version is found in the Soushenji (translated by Kenneth J. Dewoskin and J.I. Crump, Jr.):
Hua T’o Cures an Ulcer with a Dog and Two Horses (3,69)
Hua T’o (T. Yuan-hua) of the state of P’ei was also known as Hua Fu. Liu Hsün of Lang-ya, Grand Protector of Ho-nei, had a daughter who was about twenty. Her feet troubled her, and on the inside of her left thigh she had tumor [sic] that, though it did not pain her, itched. The tumor would be inactive for several weeks and then would suddenly break out. This went on for seven or eight years until finally Lu Hsün received T’o and asked him to examine her.
“This is easily cured,” said Hua T’o. “Prepare a brown dog, the color of rice chaff, and have two sound horses procured.” Hua T’o then tied a rope to the dog’s neck, and the horse was made to drag the dog at a gallop. When the first horse was exhausted he was exchanged for the other until at least thirty li had been covered. By then the dog could no longer walk, so a man was detailed to drag it until a total of fifty li had been traveled.
The girl was then drugged. When she was comfortable and unconscious, the dog’s belly, at a place near the hind leg, was opened with a great knife. This wound was placed two or three inches from the site of the girl’s ulcer, and a serpentine creature was observed coming forth from it. An iron awl was thrust through the serpent’s head parallel to the girl’s leg. The thing wriggled beneath the girl’s skin for some time but eventually grew still and was drawn out.
The creature was about three feet long and was clearly a snake. However, though it had eye sockets, it had no eyeballs and its scales faced forward.
Salve was later spread on the ulcer, and the girl was cured in seven days.
Another, abbreviated, version of this is found in Tale 323 in the Tang-era collection Du Yi Zhi 獨異志 (Outstanding Fantastic Stories), collated by Li Rong 李冗:
In the realm of Wei there was a woman who was extremely beautiful, but had remained unmarried for a long time, because she often suffered a sore on her right knee that wept pus without cease. Encountering Hua Tuo on the road, her father questioned him about it. Tuo said: “Have someone ride a horse, pulling along a chestnut-coloured dog, and gallop for thirty li. Return, sever and hang up the dog’s right foot.” Presently, a red snake emerged from the sore and  entered the dog’s paw. Her illness was then cured.
This version was picked up and included in the tenth-century compilation Taiping guangji 太平廣記 (Extensive Gleanings from the Era of Great Harmony), where it is combined with another story of Hua Tuo’s expertise:
Hua Tuo 華佗
Hua Tuo of Wei was a skilled physician. Once, the prefectural commander became very ill. Tuo encountered him, and the commander ordered him to perform a diagnosis and treatment, but Tuo withdrew, addressing his son: “The cause of the gentleman’s illness is unusual. There is an accumulation of blood in the chest. He should be made very angry, so that it can be spat out. Then he will be able to expel the malady. Otherwise there is no chance for life. His son can speak in full about his father’s entire life’s transgressions. I withdraw and pass the responsibility to you.” The son said: “If a cure can be effected, what should not be said?” Then he detailed all his father’s misdeeds and mistakes, telling all to Tuo. Tuo therefore composed and left a letter scolding the man. The father grew extremely angry, dispatching clerks to arrest Tuo, but Tuo did not come back. He then vomited more than a sheng (about a litre) of black blood. His illness was then cured. Moreover, there was a woman who was extremely beautiful, but had remained unmarried for a long time, because she often suffered a sore on her right knee that wept pus without cease. Encountering Hua Tuo on the road, her father questioned him about it. Tuo said: “Have someone ride a horse, pulling along a chestnut-coloured dog, and galloping for thirty li. Return, cook and sever the dog’s right foot, then attach it to the sore.” Presently, a red snake emerged from the sore and  entered the dog’s paw. Her illness was then cured.
 Gan Bao, Kenneth J. Dewoskin and J.I. Crump, Jr. (trans), In Search of the Supernatural: The Written Record (Stanford, CA: Stanford University Press), p.41. Soushenji 3.41:
 Li Rong 李冗, Du yi zhi, 獨異志 (Outstanding Fantastic Stories) in Du yi zhi, Xuanshi Zhi 獨異志，宣室志 (Outstanding Fantastic Stories, Stories from the Chamber of Dissemination), edited by Zhang Yongqin 张永钦 and Hou Zhiming 侯志明 (Beijing: Zhonghua shuju, 1983), pp. 65-66:
魏國有女子，極美麗，踰時不嫁，以右膝上常患一瘡，膿水不絕。遇華陀過，其父問之。陀曰：「使人乘馬，牽一栗色犬，走三十里。歸而截犬右足挂之。」俄頃，一赤蛇從瘡出而  入犬足，其疾遂愈。
 Li Fang 李昉, et al., Taiping guangji 太平廣記 (Extensive Gleanings from the Era of Great Harmony), 10 vols (Beijing: Zhonghua shuju, 1961), 218.1664-65: