EXPERIMENTS AND SECRETS OF GALEN, RASIS, AND OTHERS

II. CHEMICAL AND MAGICAL

Of the books of experiments of a chemical or magical character which we have to consider in this chapter the earliest, as far as our available information goes, is the Liber Vaccae, with which the name of Galen is associated and which is primarily a collection of magical and necromantic experiments. The original author, however, was the philosopher Plato whose work, according to a long, rambling, and confused prefatory statement, Galen had revised and abbreviated. Steinschneider held that our treatise was cited under the title Liber de prophetiis by Pedro Alfonso in the Disciplina clericalis at the close of the eleventh century,[2442] but perhaps Pedro knew it in Arabic or Hebrew[2443] rather than Latin translation. The manuscripts of the Latin translation, however, go back to the thirteenth, if not to the twelfth century,[2444] while for most of the other treatises to be considered in this chapter the oldest extant manuscripts seem to be of the fourteenth century. Moreover, William of Auvergne refers to our treatise in his work written in the first half of the thirteenth century.

The work has many other alternative titles besides Liber Vaccae, which seems to be suggested by its first experiment which is concerned with a cow, and Liber de prophetiis, which I do not remember to have seen in any Latin manuscript. Another common title is Liber Anguemis or Anequems or Anegnems or Anagnenis,[2445] although the preface explains that the treatise was not called the Liber Anguemis in the first place. The manuscripts also call it The Book of Active Institutes and The Book of Aggregations of Divers Philosophers. William of Auvergne spoke with disapproval of our treatise as a book of mixtures employed in magic, which was ascribed to Plato and called Liber Neumich or Nevemich, or the Laws of Plato. “And,” adds William sarcastically, “it is called the Laws of Plato because it is contrary to the laws of nature.”[2446] Steinschneider has pointed out that in Arabic Nawamis means “laws” and that both Neumich and Anguemis are probably Latin corruptions of the Arabic word. And of course Laws and Institutes are practically the same thing. Pico della Mirandola, writing against astrology at the close of the fifteenth century, refers to our treatise by the two titles De vacca and Institutes, warning his readers that astrologers palm off their volumes as the writings of great authorities like Aristotle, “just as magicians carry about the books of Plato De vacca and what they call the Books of Institutes, stuffed with execrable dreams and figments.”[2447]

Honein ben Ishak again appears in connection with a supposititious work of Galen. The long and repetitious prefatory statement, to which we have already alluded, is professedly by him, and we are told what Honein said and what Galen said and what Honein says Galen said in great profusion. The Latin translator, however, not to mention subsequent copyists, has perhaps taken liberties with the wording of this preface and corrupted an original Arabic clarity. Who the Latin translator is we are not told, but in some manuscripts the prefatory statement to which we have thus far alluded is proceeded by an even longer prologue which opens with the pious wish, “May God confer noble morals upon you.” This is probably the same as a prologue by “Farachius” opening, “Friend, may God grant you noble morals,” which Steinschneider held belonged with the Medical experiments of Galen or Rasis.[2448] But our prologue seems to contain a direct allusion to the following Liber vaccae[2449] as well as to be generally appropriate to it. The name of the writer of this first prologue is not given in the manuscripts I have seen, but he refers to his books concerning animals and poisons and simple medicines, which last is also called the Book of Sustenance (liber sustentationis). He appears to have been criticized for his propensity toward marvels and occult virtues and his inconsistency in at the same time censuring vulgar suspensions, incantations, and cures. His defense of occult properties is the usual one that even if reason cannot account for them, they are supported both by the testimony of the ancients and by experience. As usual the property of the magnet is adduced; the Pseudo-Aristotle is cited “in his books on stones,” and the genuine Aristotle in the History of Animals concerning the narce’s power of stupefying. The remainder of the prologue consists chiefly of a series of citations from various authors which are largely duplicated in the De mirabilibus mundi ascribed to Albertus Magnus. This first prologue cannot be by Honein, since it cites not only Costa ben Luca but filius messie, that is, Yuhanna ibn Masawaih who died at Cairo in 1015, or some Latin writer of the eleventh or twelfth century who pretended to translate his works from the Arabic. Presumably therefore it is by the Latin translator of the Liber vaccae. This could not be Faradj ben Salem under Charles of Anjou if the translation was known to William of Auvergne early in the thirteenth century.

The experiments of the Liber vaccae are hardly such as can be described in detail in English translation. Some of them are elaborate experiments in unseemly generation and obstetrics, having for their object “to make a rational animal” from a cow or ape or other beast,[2450] or “to make bees.”[2451] By a similar procedure a liniment is obtained which has such virtue that if one is anointed with it, one feels no pain from blows, while it blunts the edge of a sword with which one is struck. Or by suffumigations with it rain may be produced.[2452] A less unmentionable method of rain-making is that which is “famous among the wise” and which, the author says, some employ in his own time. First a black crow without a speck upon it is to be “submerged in water until it dies.” Then a very black dog is to be imprisoned in a dark house and given the crow to eat and the water in which it was drowned to drink on the third day. By the eleventh day, we are assured, only the whites of his eyes will show and he will be unable to bark. Then one takes a small tree called mephus with small leaves like rue and a flower like the bean, and gives the dog about an ounce of its juice, which will cause him to recover his voice and bark mightily. He should then be bound “hand and foot” (manus et pedes) and boiled in a big pot. The broth thus obtained is to be used to bring rain.[2453] Other procedures are described to stop a rainy spell and restore fine weather.[2454]

In order to see spirits a white cock with a round crest which is concave in the middle is put in a place where neither the bark of a dog nor the voice of a crow is heard, whereby this experiment is sharply distinguished from the dog-and-crow procedure. For three successive days the cock is to be fed on the eyes of three fish of the species known as alliataiu, and the eyes must have been removed while the fish were living. On the third day the cock will swell up and become aggressive and his crest will grow inflamed. After three hours he is to be decapitated and fed to a wild cat, which is then to be beheaded in its turn. Its blood and gall are to be dried and from them a concoction is to be prepared which will enable one to see spirits.[2455] A frog figures as an ingredient in a mixture which, if one merely writes with it on parchment and throws the same into a den of snakes or vipers, will excoriate and kill them instantly.[2456] The congealed blood of an ass is a constituent of a suffumigation which enables one to learn what the future holds in store of good or evil.[2457] Indeed throughout the work parts of animals are the favorite substances employed, although stones and herbs are also used.

The Liber Vaccae abounds in suffumigations, marvelous houses, golden or otherwise, and magic lamps and fires. One makes men appear in any form desired;[2458] another makes a house seem to be full of snakes;[2459] or a lamp is extinguished by opening the hands over it and is relighted by closing them.[2460] Such marvels we shall find frequently repeated in our following books of experiments. That of holding fire in the hand and not being burnt by it is here described as if quick-lime were used rather than alcohol.[2461] Other paragraphs tell how to plant seed and have it grow instantly,[2462] how to understand the language of the birds,[2463] how to answer questions about persons who are absent,[2464] how to sit under a tree and cause it to incline toward you.[2465] The last recipe calls for the teeth, nose, and bones of a dead man. But perhaps we have sufficiently illustrated the character of the Liber Vaccae. Its necromancy should have at least “provoked the silent dust” of Plato and of Galen.

To Plato and Galen, though never apparently again in partnership, were also attributed various works of alchemy in the middle ages. Most widespread would seem to have been The Fourth Book or Four Books, which is found both in the manuscripts and in print. In an Oxford manuscript[2466] it opens by Thebit, presumably ben Corat, asking Hasam to “tell us briefly what you have learned of the revelation of things occult and expound the book of old Plato.” Thebit also introduces both of the other parts of the book in this manuscript, but for the most part Hames tells us what Plato said. This indirect form of presentation is somewhat similar to that of the Liber Vaccae, and there is also much talk of abbreviating even in the fuller and different printed version,[2467] which is divided into four books, but the contents are entirely alchemical and there is no mention of Galen. The work seems to be a translation from the Arabic and not a Latin forgery. Berthelot placed the Latin translation of the alchemical treatise of the Pseudo-Plato about 1200.[2468] But there are in the manuscripts yet other works of alchemy ascribed to Plato, one of which, The Thirteen Keys of Greater Wisdom, is said to have been translated from Arabic into Latin about 1301 A. D.[2469]

As for Galen, a Commentary of Galen upon Hermes’ Book of Secrets[2470] turns out to be an alchemy of the incoherent and mystical variety. A Practice in the Secrets of Secrets of Nature ascribed to him is obviously spurious, since it opens by citing Geber. It is accompanied by a Theorica.[2471] Indeed, the Practica is really the same as the treatise usually ascribed to Archelaus.[2472] There was perhaps a medieval alchemist named Galen, since a manuscript at Paris states that “Master Galienus the writer who is used in the episcopate is an alchemist and knows how to whiten eramen so that it is as white as ordinary silver.”[2473]

The Eighty-eight Natural Experiments of Rasis[2474] are not medical but a series of magic tricks and chemical experiments. Yet they are not only ascribed to Rasis, or at least are said to be a selection from a larger work of his recently translated from Arabic into Latin at Toledo,[2475] but the translator seems to be the same mysterious Ferrarius[2476] of the Experimental Medicines, while the opening words[2477] are very similar to those of the Secrets of Galen which Gerard of Cremona is supposed to have translated, except that here we read, “You have asked me, friend Anselm” instead of Monteus.[2478] Only fragments of the treatise seem to be extant but enough of the eighty-eight experiments are preserved to illustrate their character. Serpents are assembled at a given spot by placing a snake in a perforated pot about which a slow fire is built in order to make him hiss and attract his kind. Fish are made to congregate similarly beneath the surface of a river by letting down into the water at night a lighted lantern with glass windows in its four sides.[2479] The property of alcohol (aqua ardens) of burning on the tip of a finger or from a cloth which has been dipped in it without consuming the cloth or burning the finger is termed magical. To cook an egg in cold water, it is placed in quick-lime in a vessel, then cold water is poured in and the vessel tightly closed. Other experiments are to make a ring hop about the house like a locust, to carry live coals without injury, to light a candle from the rays of the sun, to blacken the face completely. More useful seem those experiments which consist in making alcohol, turpentine, or Greek fire.

Following the three experiments just mentioned, in both the manuscripts of the Eighty-eight Natural Experiments which we have just been describing, comes The Book of Fires for Burning Enemies of Marcus Grecus.[2480] Since it is also found in other manuscripts,[2481] it would appear to be a distinct treatise from the Eighty-eight Natural Experiments, although its form is similar. Berthelot already has been impressed by the close association in this treatise of “purely scientific compounds of combustible or phosphorescent substances and the preparations of prestidigitateurs and magicians.”[2482] For instance, in an effort to make an inextinguishable fire glow-worms are pulverized and mixed with other substances and then warmed for a certain number of days in horse manure.[2483] A lamp that will shed a silvery light on everything in the house is obtained by smearing the wick with a liquid similar to quicksilver supposed to be obtained by cutting off a lizard’s tail.[2484] Or everything around will appear green, if the brain of a bird is wrapped in cloth and burned with olive oil on a green stone. If the hands are rubbed with an Indian nut or chestnut and “water of camphor,” a candle may be extinguished by opening them above it and relighted by closing the hands.[2485] Other ointments are said to keep one from being burned by a flame or by the red-hot iron in the ordeal.[2486] More scientific are the recipes for oil of sulphur, gunpowder, Greek fire, alcohol.[2487] Two of the more fantastic experiments are said to have been discovered by Aristotle for Alexander,[2488] and another cites Hermes and Ptolemy for its “prodigious and marvelous works.”[2489] The reader will have noticed the recurrence of some of the matters treated in the Natural Experiments of Rasis. Such repetitions and resemblances are common in the medieval collections of recipes and experiments.

At the close of the Book of Fires of Marcus Grecus, in one of the two manuscripts[2490] where it follows the Eighty-eight Natural Experiments of Rasis, the listing of experiments of the same sort continues without any new title and the consecutive numbering of them in the margin goes on up to one hundred and forty-four in all. It is doubtful, however, how far we may regard these additional experiments as a resumption of the text of Rasis, which had been interrupted by the work of Marcus Grecus, since we cannot arrive at an even number of eighty-eight experiments by any combination. These additional experiments instruct us how to paint an image on the wall from which a candle may be lighted, how to write letters that cannot be read unless the material upon which they are written is placed near a fire or touched with a rod, how to make cooked meat seem raw and wormy.[2491] This trick, which is found frequently in medieval manuscripts, is performed by making mince meat of the heart or dried blood of some animal and strewing the particles upon the piece of cooked flesh, whose heat will make them move like worms, while their color is that of raw meat. We are also instructed how to cook meat of a sudden, how to turn a red rose white—apparently by fumigating it with sulphur, and how to make “marvelous bottles” (ad faciendum ampullas mirabiles)—the directions seem to tell how to blow soap bubbles.[2492] How to emit fire from the mouth, to heat a bath, to construct an artificial mill in a camp, and to make all the bystanders appear headless.[2493] A score of experiments are concerned with colors and dyes.[2494] To make a dog follow you, place a piece of bread and butter under your armpit, “that it may receive the odor of the sweat,” and then feed it to the dog.[2495] A magical experiment to deprive a man of his urine consists in taking urine and earth on which someone has made water and enclosing them together in the skin of a camel’s womb or a dog’s paw; “and he will have no urine as long as the earth is enclosed in the skin.”[2496] The last experiment, “that a wife may live a good life with her husband,” involves writing an incantation upon parchment.[2497]

Found together with the Eighty-eight Natural Experiments of Rasis in one of the two manuscripts[2498] containing that work, and in other manuscripts together with the Liber ignium[2499] and Liber Vaccae[2500] and Experiments or Secrets of Albert,[2501] is an anonymous work entitled The Secret of the Philosophers. As it seems to be found especially in English libraries,[2502] and mainly in manuscripts of the fourteenth century,[2503] it was perhaps composed in England in the thirteenth century. At any rate it claims no connection with Galen or Rasis. It is longer than most medieval collections of experiments and subdivides into seven sections, each named after one of the liberal arts.

Under the heading “Grammar” materials and instruments used in writing are first spoken of, then methods of writing, especially those employed by the wise to conceal their meaning, as when the alchemists use the names of planets to denote the seven chief metals. Instructions are given for making colors employed in illuminating, ink, white tablets, and glues. We are told again how to write letters which are invisible until touched with a rod or exposed to fire. Also how to write so that the writing can be read only in a mirror, how to erase writing without leaving any mark, how to engrave steel and other metals, and how to color the letters so engraved. A paragraph on the right way of speaking might seem to belong under the head of rhetoric rather than of grammar, but just precedes the section of rhetoric in such manuscripts as I have examined. It warns against much speaking, citing Aristotle’s advice to Alexander in the Secret of Secrets, and ends with the familiar couplet:

The section on “Rhetoric,” which is defined as speaking ornately, is devoted to riddles, verbal deceits, quibbles, and catches. Under one of its sub-heads, Of Weights, we are told how to balance a knife, although its center is to project beyond the edge of a table and although a weight is to be hung on this projecting end. “The way to fulfill the doctrine of this thing is to fix the blade of the knife in the end of a rod so that it makes an acute angle with the rod, and you will see how the rod will hang with the knife.”

“Dialectic” is concerned in our treatise not with logical fallacies but with deception of the senses by various tricks. To make water look and taste like wine, a bottle half full of water should be held or left inverted for a time over the orifice of a jar of wine. This procedure is recommended in cases where a patient wants to drink wine and the doctor knows that it would not be good for him. In order to determine whether a patient is really dead and to prevent cases of burial alive, it is recommended to hold a mirror to his nostrils and see if it will be clouded by a faint breath. This comes under the sub-head, De olfactus deceptione, breathing as well as the sense of smell evidently being included under the olfactory organs. The sense of hearing is deceived by an echo, and the sense of sight by mirrors which enlarge or multiply objects or make an image appear outside the mirror. The use of burning glasses is also discussed.

Under the sub-head, “Sophistries called sleight-of-hand,” (De sophisticationibus que vocantur iugulationes), come the tricks or cautelae of the jugglers. An apple is made to move on a table by preparing a hole in the center beforehand and placing a beetle inside. To construct a cross that will seem to turn to right or left automatically in answer to questions put to it concerning hidden or future matters, one builds it up of wax about the tail of some insect or tiny animal[2505] which is also concealed in wax and irritated with sage[2506] so that it wiggles its tail and the cross. Hands that have been bound may be freed by cutting the rope against a prearranged knife. Again we meet the experiments to make cooked meat seem raw or full of worms and directions for blowing soap-bubbles, a process which is spoken of as “making a golden sphere appear flying in the air.” Other illusions under “Dialectic” are to seem on fire and not be burned, to see stars in the daytime by multiplying the reflections of the sun, to make a silver coin seem copper, and to deceive the sense of touch by such methods as holding an object between two crossed fingers.

The headings, Arithmetic, Music, and Geometry, are more exactly appropriate to their contents than Dialectic was. One problem in arithmetic is to tell how many knights, esquires, and pages will be required to divide twenty loaves of bread, if each knight receives two loaves, if two pages share a loaf, and if four esquires share a loaf. Under geometry are calculated surfaces, the cubic contents of various receptacles, and the altitudes of inaccessible objects.

Under “Astronomy” the rule of superiors over inferiors is affirmed and the various attributes, properties, and effects of the planets are listed. Then come “experiments with air” and many figures of vessels partly filled with water or other liquids. Siphoning is explained under the heading, “Of the ascent of water on account of the consumption of the air lest a vacuum be left.” By employing the same principle that Adelard of Bath observed in the magic water-jar of the enchantress, any one of four different liquids that the spectators choose can be poured from a single faucet. Inside the jar are four compartments each with its own airhole above and outlet below, and beneath all four a common chamber into which they open and from which the common faucet pours. The four air-holes are covered with the fingers, and as one of these is raised, the liquid will flow from the corresponding compartment. This is illustrated by a diagram of the contrivance. The magnet is discussed under “Astronomy” “because it bears in itself a likeness of the sky.” This discussion of the magnet and some of the accompanying figures resemble the treatise of Peter Peregrinus on the magnet, which was written in the thirteenth century.[2507] Here the work ends in two of the three manuscripts which I have used,[2508] but in the third further experiments are added.[2509] Some of these have occurred before in the Secretum philosophorum itself, or in other experimental treatises of which we have already spoken. Others are to make fireworks,[2510] to soften steel, to drive away crows, and to tell whether a person is a leper.

Not to be confused with the Latin Secretum philosophorum, which we have just described and which seems to be of English origin, is a work in the French vernacular written at the end of the thirteenth century and entitled Le Secret aux philosophes.[2511] It is not a collection of experiments but rather an encyclopedic discussion of theological and metaphysical as well as natural problems in the form of a dialogue, presumably imaginary, although sometimes represented as a translation, between Placides, the promising son of a petty king, and his master Timeo, who chose him as his pupil in preference to the stupid son of a great emperor. Through this medium is retailed for less learned perusal much of the knowledge and superstition, especially astrological, to be found in the Latin and Arabic learning of the time. Perhaps the resemblance is greater to the Secret of Secrets of the Pseudo-Aristotle than to any other treatise that we have considered. The author, very weak and meager on theological and metaphysical matters, shows a much greater interest in natural science and something of the spirit of experimental research. Yet in a prologue “the compiler” gives his name as Jehan de Bonnet, priest, doctor of theology, and native of Paris. Ernest Renan was impressed by the curiosity shown concerning problems of natural science, by the “search after realities” and by the experimental spirit of the book. The solutions, as in the Natural Questions of Adelard of Bath, often make one smile, but “this naïve composition ... is superior to many scholastic treatises in Latin which deal purely with abstractions and where modern thought has not its true antecedents.” In this treatise, on the other hand, “the science of reality has taken the upper hand” and “the idea of research is born.”[2512] But Renan was mistaken in thinking such scientific curiosity a new thing as late as the close of the thirteenth century, and perhaps on that account overestimated its importance in this case.

Returning to books of experiments, we may note a treatise whose contents are very similar to the Eighty-eight Natural Experiments of Rasis, the Book of Fires of Marcus Grecus, and the Secretum philosophorum, namely, Some experiments which King Solomon composed because of his love for, and the imploring of, a most excellent queen, and they are experiments of nature.[2513] Instead of the experiment with the snake in the pot we now have rats in a cage, whose squealing when a fire is heated is supposed to attract other rats. Again we are told how to write invisible letters, how to make a candle burn in water,[2514] how to light a candle from the mouth of an image painted upon the wall. This is done by painting the mouth with sulphur and turpentine and applying the wick of the candle to it just after the candle has been blown out and before it has quite ceased to glow. Quicklime as well as sulphur and turpentine are used in an image that will illuminate and take fire when water is poured over it. Quicksilver is placed with saltpeter and sulphur inside a ring in order that it may hop about when put near a fire.

Such experiments sometimes occur without any title as well as without name of author, as in a manuscript where there are a dozen leaves filled with them between the treatise on plantations and the experiments or secrets ascribed to Albert.[2515] Again we encounter the jumping ring, the cooked meat turned raw, men made to appear headless, and artificial thunder which seems produced by use of gunpowder. There is much discussion of colors and alchemy and we are told how to make sal ammoniac and “the best bitumen.”[2516] But the virtues of herbs and animals are not forgotten and many of the experiments are medical or magical. Instructions are given for making a white crow by tampering with the crow’s egg, and how to make human hair grow again by the application of the ashes of a mole, burned in a new pot, mixed with honey. A cure for diarrhoea is to drink milk in which a glowing iron has been quenched. Suspending the tongue of a goose over a sleeper has the appropriate effect of causing him to reveal all his secrets, while the suspension of the head of a bat prevents his waking. The bearer of the herb aristologia is safe from demons whether awake or asleep. To escape from chains one should employ an incantation which contains allusions to the rescue of the apostle Peter from the sea and from prison.

Frequently found in the manuscripts are twelve experiments with pulverized snakeskin which John Paulinus or John of Spain excerpted from the book in Arabic of the physician or physical scientist, Allchamus or Alchanus or Alanus or Alganus, or whatever his name may have been,[2517] a book entitled Life-Saver (Salus vitae).[2518] This work, as John further informs us at its beginning, he discovered when he “was in Alexandria, a city of the Egyptians.”[2519] Steinschneider listed this John Paulinus as a different person from the well-known twelfth century translator, John of Spain, but at least in one manuscript[2520] he is called both John of Spain and John Paulinus.[2521]

Another manuscript[2522] presents our treatise under the amusing caption, “Twelve experiments with snakeskin and some of them true.” All due credit should be given for such partial scepticism but it might well have been made more sweeping. The snakeskin is to be pulverized when the moon is in the first degree of Aries, and one manuscript adds that this must be the full moon.[2523] This powder will heal a wound in the head, or will keep the head from being wounded, if it is sprinkled on the hair. A face, washed with it and water, is terrible to foes and secures the faithful allegiance of friends. If the powder is scattered in an enemy’s house, he will be unable to remain there. To secure an attentive hearing in a council, sprinkle a little at your feet. Place some on the tip of the tongue, and you will be invincible in scientific disputations. “And this has been tested many times.” This healing and magic powder also enables one to see into the future, to learn another’s secrets, to insure the fidelity of a servant or messenger, to guard against poison, to win the love of a woman. If a leper eats some of it, his disease will grow no worse. This last experiment is perhaps suggested by Galen’s story of the cure of skin disease by drinking wine in which a viper had died.

At the end of these twelve experiments one manuscript adds that “John in the same book gives additional statements which Alcanus composed,” and continues with further suggestions concerning the medicinal preparation and uses of snakes and their skins and blood.[2524] Similar are Secrets concerning the Serpent, which, according to a manuscript of the fifteenth century in the Bodleian, Albertus Magnus gave to a doctor of sacred theology of the order of Friars Minor at Nürnberg,[2525] and which direct how to prepare snakes and recount their medicinal virtues. It will be recalled, too, that in our preceding chapter we treated of the Experiments of Nicholas of Poland which made considerable use of pulverized snakes or toads or scorpions, and which are sometimes found in the same manuscripts[2526] as the Twelve Experiments with Snakeskin.

Perhaps this is the same Nicholas to whom chemical experiments are attributed in two Oxford manuscripts.[2527] In the fuller manuscript these experiments are numbered in the margin from one to twenty,[2528] but sometimes more than one recipe or item is found under a number.[2529] Besides some alchemistic generalizations, such as the opening sentence which states that there are seven bodies, namely, Saturn, Jupiter, Mars, Sun, Venus, Mercury, and Moon, and a recipe or two for making gold and silver, the treatise consists of instructions for the preparation of such chemicals as sal ammoniac, quicksilver, arsenic, sulphur, and common salt, and of other recipes similar to those in the Book of Fires of Marcus Grecus.[2530]The author frequently cites the books and experiences of the philosophers but also speaks of his own experiments. Once, for example, he supports the assertions of the philosophers by adding, “And I, Nicholas, say that I have tested these two operations experimentally”:[2531] in another place he says of a powder recommended “by a very wise philosopher” that he has not yet experienced it himself as the operation is long and difficult.[2532]