Since the ideas expressed in Dengshe were to have such an enormous influence on later unicorn myths, it is important to examine them in greater detail.
1) The tongtianxi (communicating with the sky rhinoceros horn): This type of rhino horn was further defined in the commentaries on Baopuzi which were also written during the fourth century C.E. There, alchemists speculated that this particular horn was perforated from top to bottom and contained a marvellous substance which grew towards the tip of the horn, creating a star-shaped opening from which was emitted qi. By means of this qi, the magical horn of the rhinoceros was able to communicate with heaven and the world of the spirits.
We have no means of scientifically establishing the identity of the kind of rhinoceros horn which was known to the Chinese as the tongtianxi. It may be that it was simply a term they used to designate a particularly rare type of rhino horn. Nevertheless, it was probably the horn of an Asian species, since all Asian rhinoceros horns have, in addition to their traverse banding, a distinctive groove on the exterior which runs longitudinally toward the tip, a feature which does not appear on African rhino horns (Chapman, 1999, 51). This unique groove may have provided the inspiration for the idea of the vein running through the tongtianxi with which it communicated with the sky.
2) Water dispelling: According to Ge Hong, it was only one particular type of rhino horn, the tongtianxi, that had the magical power to dispel water. Nevertheless, people later came to believe that this was a general characteristic of all rhinoceros horns. From ancient times the eastern part of Sichuan called Ba was famous for its colossal species of rhinos (Laufer, 1914, 162-3), and according to Chinese records, the governor of Sichuan Province had stone sculptures of rhinos made “to suppress water” (Sun, 1982, 82). Even as late as the fourteenth century, when people no longer had any idea of what a real rhinoceros looked like, a cast iron sculpture of a seated rhinoceros-unicorn with a single (upside down) horn in the middle of its forehead, was placed beside the Huang River near Kaifeng in Henan Province to ward off flooding (colour plate 36).
Plate 36. Huang River iron rhinoceros-unicorn, near Kaifeng. Early Ming Dynasty, 14th century.
The custom of installing iron sculptures of rhinoceros-unicorns as well as iron and bronze ox-unicorns (which were known as “flood-suppressing beasts”) to serve as supernatural guardians of China’s waterways, survived until the end of the nineteenth century (fig. 66) (Yao, 2000, 289-90).
Figure 66. Bronze ox-unicorn at the Summer Palace, Beijing. Qing Dynasty
ROM Far Eastern Archive photo
This Chinese belief in the hydraulic power of the mythic rhinoceros-unicorn is particularly intriguing, for it may have arisen from a later misinterpretation of the ideas inherent in the ancient character fa (legal justice) (fig. 67).
Figure 67. Development of the fa (legal justice) character
This character, as noted earlier, contains the elements zhi ‘unicorn,’ plus qu ‘to get rid of,’ plus shui ‘water.’ Originally, in the Western Zhou character, the element qu meant ‘to get rid of evil-doers,’ while the character shui was included to indicate ‘impartiality of judgement’ because water always reaches its own level. By the Han Dynasty however, due to the standardization of the Chinese script, the character fa no longer contained a recognisable goat-unicorn zhi element. As a result, the identity of the mythic goat-unicorn element became obscured. Thus people may have thought that the element qu was directly related to the element shui, and concluded that this combination meant ‘to get rid of water.’
3) The haijixi: Ge Hong clearly states that the people of South China use the term haijixi (fowl-frightening rhinoceros horn) as a local term to designate the tongtianxi (communicating with the sky rhinoceros horn.) This southern term haijixi is recorded as early as the fourth century B.C.E. in the Zhangguoce (War Policy of the Warring States Period) at the time of Zhang Yi when the King of Chu despatched a hundred chariots to present haijixi and yeguanbi (jade discs resplendent at night) to the King of Qin. During the Han period, when rhinoceros horns were imported into China via the southern seaports, this term is often the one used in early Chinese texts, where it is listed among the bao (precious things) brought to China as tribute by foreign countries to the south.
The idea of the tongtianxi as a bao (precious thing) containing a red vein or some kind of marvellous substance, may have given rise to the later Muslim and European beliefs that a precious red “ruby” or “carbuncle” (these names were interchangeable during the Middle Ages) was to be found hidden at the base of the unicorn’s horn.
The male carbuncle was regarded as the king of stones. Whether used as an amulet or crushed in wine, it was held to withstand poison, preserve from plague, banish sadness and evil thoughts and terrifying dreams. A good one was supposed to shine by night and to be visible through clothing. It was occasionally made an emblem of Christ. In a few instances, all early, the carbuncle at the base of the unicorn’s horn seems to have been regarded as the source of the horn’s magic properties. (Shepard,  1982, 291 n.102)
There is no doubt that from ancient times in China rhinoceros horns were considered to be as precious as jade or jewels. Much later, a symbol consisting of two rhinoceros horn cups was included among the ba bao (Eight Precious Things) which became ubiquitous among Chinese design motifs as a symbol of longevity and good fortune (fig. 68).
Figure 68. Symbol of a pair of rhinoceros horn cups.
One of the “Eight Precious Things”
4) Does not contract humidity: Ge Hong says that the tongtianxi does not contract humidity in a wet environment. This is true, of course, because rhino horn is simply composed of bundles of compacted keratin, and so, like hair or fingernails, it does not sweat. But true horns do not sweat either. So why did Ge Hong include this among the attributes of the tongtianxi? Most likely the reason was in order to contrast it with the behaviour of rhino horn in the presence of poison, when it was thought to “sweat” (see below).
5) The shining horn: This truly wondrous idea, that the horn of the rhinoceros shines like the fire of a torch at night, was taken up and repeated in endless variations in later Chinese texts. For example, in the Weiguotong (History of the Wei Dynasty,) which was written by Liang Zuo sometime during the Northern and Southern Dynasties period, it says: “In the territory of the Barbarians of the Southwest there is a strange rhinoceros with three horns. When walking in the evening it looks like a big torch which can shine several thousands of feet away.” This idea of a yemingxi (night-shining horn) was still current in the Tang Dynasty, where it appears in the Duyang zabian (Duyang Anthology of Various Things) written by Su E in the latter part of the ninth century.
In the first year of the period Baoli (825 C.E.) of the Emperor Jingzong of the Tang Dynasty, the country of Nanchang offered to the court a yemingxi (night-shining rhinoceros horn). In shape it was like the tongtianxi (rhinoceros horn communicating with the sky). At night it emitted light, so that a space of a hundred paces was illuminated. Manifold silk wrappers laid around it could not hide its luminous power. The Emperor ordered it to be cut into slices, and worked up into a girdle, and whenever he went out on a hunting expedition, he saved candlelight at night.
Thus it is clear that the concept of the yemingxi (night-shining rhinoceros horn) survived in Chinese texts at least until the later Tang Dynasty. However, we have no earthly way of knowing the nature of this mysterious kind of bioluminescent rhino horn, for in reality, the horn of the rhinoceros does not glow in the dark. Perhaps this “night-shining” attribute was simply meant to emphasize its preciousness, by making it akin to the yeguangbi (jade discs resplendent at night). Nevertheless, in the case of the yeguangbi there is at least the possibility that these discs were made from some kind of phosphorescent mineral or mica, rather than jade.
According to F. Hirth, “the shining stone par excellence… seems to be the chlorophane…. an emerald possessing the power of reflecting after dark the rays received from the sun during the day time” (Hirth, 1885, 243). Yet regardless of the true nature of the yemingxi, knowledge of this ancient Chinese belief in the magical night-shining quality of particular rhino horns was carried westward, and provided the inspiration for the Western belief in the magical shining horn of the unicorn. Even today, a lingering memory of this splendid quality continues to impart a bright loveliness to some modern Western images of unicorns.
6) The test for poison: The ancient Chinese use of rhinoceros horn both as an antidote to, and a test for poison has been discussed in detail earlier. There is absolutely no doubt that these ideas originated in China, for as Laufer says, “Neither in ancient India nor in the (Western) classical world do we find any trace of such beliefs as those expounded by Ge Hong and his successors, not a particle of all that Chinese natural philosophy of the horn” (Laufer, 1914, 54, n.). Later in West Asia and Europe, these ideas would provide the source of the magical notion that a true unicorn’s horn would “sweat” in the presence of poison. This idea of “sweating” no doubt derived from the ancient Chinese test for the presence of poison, whereby a white foam would arise “when poisonous medicines of liquid form were stirred with a rhinoceros horn hairpin.”
7) Gu poison: Ge Hong warns that when having a meal in a foreign country, or when threatened by gu poison, the food should be stirred with a rhinoceros horn hairpin, in order to detect the presence of poison. The character gu meaning “internal worms,” “poison” and “insanity” appears in the oracle bone script of the late Shang Dynasty as a pictograph of a bowl full of worms (fig. 69).
Figure 69. Development of the gu (poison) character
Needless to say, insects in vegetables and maggots in rotting meat must have been common sights in Shang times. Thus it would have been easy for people to come to the conclusion that afflictions such as diarrhoea or toothache, etc., were caused by ingesting worms (Hsü, 1996, 689).
According to H. Y .Feng and J. K. Shryock, sufficient ideas and practices are grouped together under the Chinese term gu to justify the use of the phrase “black magic” (i.e., magic whose purpose is harmful). However, gu refers only to certain particularly nasty kinds of black magic which were used to acquire wealth and revenge. The method used to create the gu poison was to place poisonous snakes and insects together in a covered vessel until only one creature survived. This was called the gu. The poison concentrated in this gu was taken and administrated in food and drink to the victim, who then became ill and died. In general, the gu was regarded as a malignant spirit which then acquired the wealth of its victim for the sorcerer (Feng and Shryock, 1935, 1).
This particular connection, between rhinoceros horn and gu poison, was to continue to resonate down through the ages to a time and place far distant from its origin in ancient China. In Venice, in the sixteenth century, where the existence of the unicorn and the magical properties of its horn were simply taken for granted, the only problem was to establish whether the unicorn’s horn (alicorn) was genuine or not, so that its efficacy could be assured. David de Pomis, writing in 1587 C.E., described the following as a true test for unicorn’s
The test is this: place the horn in a vessel of any sort of material you like, and with it three or four live and large scorpions, keeping the vessel covered. If you find four hours later that the scorpions are dead, or almost lifeless, the alicorn is a good one, and there is not money enough in the world to pay for it. Otherwise it is false. (Shepard,  1982, 117)
Thus, although the purpose has altered somewhat, the idea of putting poisonous scorpions in a covered vessel is analogous to the ancient Chinese practice of placing poisonous snakes and insects in a covered vessel to create the gu. Most interesting in this regard is the painting on the left wing of an early sixteenth-century altarpiece by Jerome Bosch, now in the Museo del Prado, Madrid. The subject of the painting is The Garden of Eden, and an image of it has been reproduced in Freeman, 1976, plate 62. On the left, a white unicorn dips its horn into a stream to purify the water, while on the right, small poisonous creatures and insects scurry out of the same stream, rendered harmless by the unicorn’s action.
The third and last meaning of the character gu is ‘insanity’ or ‘disease of the mind.’ This idea can be illustrated by a passage from the Zuo Zhuan (The Zuo Commentary) as follows:
In the first year of Duke Zhao (541 B.C.E.), the Marquis of Jin asked the help of a physician from Qin, and the Earl of Qin sent one named He to see him. He said: ‘The disease cannot be cured. It is said that when women are approached [too frequently] the result is a disease resembling gu. It is not caused by a spirit nor by food [like the usual gu methods of magic]; it is a delusion which has destroyed the mind.’ When asked what he meant by gu, He replied: ‘I mean that [disease] which is produced by excessive sexual indulgence.’
Essentially this means that when a man becomes obsessed, especially with women and sex, he loses his sense of judgement. He is, in the most profound sense “mad with love” and cannot think straight about anything else. “The fundamental idea of gu as a disease is based on an analogy. The human body is regarded as a vessel, into which the disease spirits enter like insects. Many early peoples have regarded disease as due to the possession of the body by an alien spirit” (Feng and Shryock, 1935, 2-3). Thus it would appear that the basic idea behind the definition of gu as “insanity,” is to be so obsessed with women and sex that you lose your soul.
Two other interesting ideas discussed by Feng and Shyrock are that dogs were killed to ward of gu (a Chinese apotropaic practise dating from ancient times,) and that the gu spirit was afraid of hedgehogs, which were therefore extremely effective against it and its poisonous influence (Feng and Shryock, 1935, 14). Perhaps this may help to account for the presence of hedgehogs in European scenes of unicorns, and also the Renaissance belief in the power of the bezoar-stone, a calculus or gallstone “composed of calcium phosphate and hair, found in the intestines of certain Oriental sheep, goats, monkeys, and hedgehogs” (Shepard,  1982, 128) to detect the presence of poison.
8) Feeds on poisonous plants: This statement by Ge Hong, that the rhinoceros feeds on poisonous plants, thorns and brambles no doubt led to the belief in the “prickly tongue” of the karkadann (rhinoceros-unicorn) which is found in Muslim texts. In other words, they believed that its tongue must have been especially tough and thorn-proof in order to eat such unpalatable fare. These texts include “the lurid account of al-Gharnati (repeated by al-Damiri) of how the kings of China tortured a person by having him licked by a karkadann, a treatment which separated the flesh from the bone” (Ettinghausen 1950, 103). This is, of course, is complete nonsense, and only serves to emphasize the fact that “ferociousness seems altogether the foremost feature shared by all the Muslim unicorns” (ibid., 66).
Nevertheless, this Muslim concept is extremely interesting, because this idea of the karkadann’s bellicose nature is obviously a confused echo of the implacable nature of the Chinese mythic unicorn zhi which butted evil-doers with its horn. This misunderstanding occurred because Muslim artists had no direct knowledge of the ancient role played by the unicorn zhi. Thus the fierceness of the unicorn in the cause of justice under the law was misconstrued, and as a result, Muslim unicorns are often depicted as terrible monsters, fighting with elephants, lions, and other dangerous mythic beasts. It should be noted here that Richard Ettinghausen’s masterful study The Unicorn (1950), is a rich source of unicorn lore in the Muslim world. However, his conclusions about Chinese influences on Muslim unicorn iconography are necessarily flawed by his lack of access to the ancient Chinese sources on the mythic unicorn zhi, the early history of the rhinoceros, and the magical aspects which became attributed to the mythic rhinoceros-unicorn horn by the fourth century C.E. in China.
This misconception about the fierceness of the unicorn is found even earlier, in the Christian bible. As Robert Graves says,
The unicorn’s wildness and untameability had become proverbial in early Christian times because of the text in Job, XXXIX, 9: “Will the unicorn be able to serve thee or abide by thy crib?” and this Biblical unicorn, (a mistranslation by the Septuagint of rem, the Judaean aurochs or wild ox) became identified with the goat-stag, the hirco-cervus of Dionysian mysteries, which was another wild untameable animal. (Graves,  1972, 256)
9) The moveable horn: As has been noted earlier, the so-called ”horn” of the rhinoceros is not true horn. It is not fixed in its skull, and thus can be knocked off accidentally, and a new one regrown. But there is no basis in fact for Ge Hong’s assertion that the rhino sheds its horn annually. By his time however, in the fourth century C.E., very little was known in China about the real habits of the rhinoceros. It may be that his notion of replacing a horn “shed” by a rhinoceros with a wooden imitation is simply a vague memory of the Han dynasty practice of burying wooden and pottery imitations of rhinoceros horns in tombs as cheap substitutes for these “precious things.”
The Chinese, who were familiar with the rhinoceros in ancient times, were aware that the rhino’s horn was not firmly embedded in its skull. But the fantastic idea that the horn could actually move never occurred to them. Nevertheless, this idea is very ancient in the West, going back to the classical period. According to Pliny, the rhinoceros has “moveable horns several cubits long, which it can alternately raise in combat and turn straightforward or obliquely, according to opportunity.” In addition, al-Biruni (late tenth-early eleventh century C.E.), when speaking of the African rhinoceros, says that its second and longer horn becomes erect as soon as the animal wants to ram with it (Laufer, 1914, 155, n.). Eventually in the West, this idea of the mobility of African rhinoceros horns led to the conclusion that the unicorn’s horn was also capable of erection (Shepard,  1982, 104-5). The sexual implications of this are, of course, obvious, and these in turn gave rise to the kind of erotic unicorn imagery which appeared in Europe in the nineteenth century.
Having examined in detail the ancient Chinese ideas about the marvellous powers of rhinoceros horn, which were enumerated so long ago by the Daoist adept Ge Hong, it is impossible to deny their tremendous impact on later beliefs in the magical attributes of the rhinoceros-unicorn’s horn. The fact that the physical appearance of the unicorn was to change dramatically over time and space did nothing to dispel these fantastic ideas about the powers inherent in its horn. As Odell Shepard has said, it is amazing, in fact, “how much the legend of the unicorn, and especially the belief in the magic virtues of its horn, owes to the rhinoceros” ( 1982, 133).