nt。 This was the field of medicine。 The Byzantines of this time could boast of two great medical men； Aetius of Amida （about 502…575 A。D。） and Paul of Aegina （about 620…690）。 The works of Aetius were of value largely because they recorded the teachings of many of his eminent predecessors； but he was not entirely lacking in originality； and was perhaps the first physician to mention diphtheria； with an allusion to some observations of the paralysis of the palate which sometimes follows this disease。 Paul of Aegina； who came from the Alexandrian school about a century later； was one of those remarkable men whose ideas are centuries ahead of their time。 This was particularly true of Paul in regard to surgery； and his attitude towards the supernatural in the causation and treatment of diseases。 He was essentially a surgeon； being particularly familiar with military surgery； and some of his descriptions of complicated and difficult operations have been little improved upon even in modern times。 In his books he describes such operations as the removal of foreign bodies from the nose； ear； and esophagus； and he recognizes foreign growths such as polypi in the air…passages； and gives the method of their removal。 Such operations as tracheotomy； tonsellotomy； bronchotomy； staphylotomy； etc。； were performed by him； and he even advocated and described puncture of the abdominal cavity； giving careful directions as to the location in which such punctures should be made。 He advocated amputation of the breast for the cure of cancer； and described extirpation of the uterus。 Just how successful this last operation may have been as performed by him does not appear； but he would hardly have recommended it if it had not been sometimes； at least； successful。 That he mentions it at all； however； is significant； as this difficult operation is considered one of the great triumphs of modern surgery。 But Paul of Aegina is a striking exception to the rule among Byzantine surgeons； and as he was their greatest； so he was also their last important surgeon。 The energies of all Byzantium were so expended in religious controversies that medicine； like the other sciences； was soon relegated to a place among the other superstitions； and the influence of the Byzantine school was presently replaced by that of the conquering Arabians。
THIRTEENTH…CENTURY MEDICINE The thirteenth century marks the beginning of a gradual change in medicine； and a tendency to leave the time…worn rut of superstitious dogmas that so long retarded the progress of science。 It is thought that the great epidemics which raged during the Middle Ages acted powerfully in diverting the medical thought of the times into new and entirely different channels。 It will be remembered that the teachings of Galen were handed through mediaeval times as the highest and best authority on the subject of all diseases。 When； however； the great epidemics made their appearance； the medical men appealed to the works of Galen in vain for enlightenment； as these works； having been written several centuries before the time of the plagues； naturally contained no information concerning them。 It was evident； therefore； that on this subject； at least； Galen was not infallible； and it would naturally follow that； one fallible point having been revealed； others would be sought for。 In other words； scepticism in regard to accepted methods would be aroused； and would lead naturally； as such scepticism usually does； to progress。 The devastating effects of these plagues； despite prayers and incantations； would arouse doubt in the minds of many as to the efficacy of superstitious rites and ceremonies in curing diseases。 They had seen thousands and tens of thousands of their fellow…beings swept away by these awful scourges。 They had seen the ravages of these epidemics continue for months or even years； notwithstanding the fact that multitudes of God…fearing people prayed hourly that such ravages might be checked。 And they must have observed also that when even very simple rules of cleanliness and hygiene were followed there was a diminution in the ravages of the plague； even without the aid of incantations。 Such observations as these would have a tendency to awaken a suspicion in the minds of many of the physicians that disease was not a manifestation of the supernatural； but a natural phenomenon； to be treated by natural methods。 But； be the causes what they may； it is a fact that the thirteenth century marks a turning…point； or the beginning of an attitude of mind which resulted in bringing medicine to a much more rational position。 Among the thirteenth…century physicians； two men are deserving of special mention。 These are Arnald of Villanova （1235…1312） and Peter of Abano （1250…1315）。 Both these men suffered persecution for expressing their belief in natural； as against the supernatural； causes of disease； and at one time Arnald was obliged to flee from Barcelona for declaring that the 〃bulls〃 of popes were human works； and that 〃acts of charity were dearer to God than hecatombs。〃 He was also accused of alchemy。 Fleeing from persecution； he finally perished by shipwreck。 Arnald was the first great representative of the school of Montpellier。 He devoted much time to the study of chemicals； and was active in attempting to re…establish the teachings of Hippocrates and Galen。 He was one of the first of a long line of alchemists who； for several succeeding centuries； expended so much time and energy in attempting to find the 〃elixir of life。〃 The Arab discovery of alcohol first deluded him into the belief that the 〃elixir〃 had at last been found； but later he discarded it and made extensive experiments with brandy； employing it in the treatment of certain diseasesthe first record of the administration of this liquor as a medicine。 Arnald also revived the search for some anaesthetic that would produce insensibility to pain in surgical operations。 This idea was not original with him； for since very early times physicians had attempted to discover such an anaesthetic； and even so early a writer as Herodotus tells how the Scythians； by inhalation of the vapors of some kind of hemp； produced complete insensibility。 It may have been these writings that stimulated Arnald to search for such an anaesthetic。 In a book usually credited to him； medicines are named and methods of administration described which will make the patient insensible to pain； so that 〃he may be cut and feel nothing； as though he were dead。〃 For this purpose a mixture of opium； mandragora； and henbane is to be used。 This mixture was held at the patient's nostrils much as ether and chloroform are administered by the modern surgeon。 The method was modified by Hugo of Lucca （died in 1252 or 1268）； who added certain other narcotics； such as hemlock； to the mixture； and boiled a new sponge in this decoction。 After boiling for a certain time； this sponge was dried； and when wanted for use was dipped in hot water and applied to the nostrils。 Just how frequently patients recovered from the administration of such a combination of powerful poisons does not appear； but the percentage of deaths must have been very high； as the practice was generally condemned。 Insensibility could have been produced only by swallowing large quantities of the liquid； which dripped into the nose and mouth when the sponge was applied； and a lethal quantity might thus be swallowed。 The method was revived； with various modifications； from time to time； but as often fell into disuse。 As late as 1782 it was sometimes attempted； and in that year the King of Poland is said to have been completely anaesthetized and to have recovered； after a painless amputation had been performed by the surgeons。 Peter of Abano was one of the first great men produced by the University of Padua。 His fate would have been even more tragic than that of the shipwrecked Arnald had he not cheated the purifying fagots of the church by dying opportunely on the eve of his execution for heresy。 But if his spirit had cheated the fanatics； his body could not； and his bones were burned for his heresy。 He had dared to deny the existence of a devil； and had suggested that the case of a patient who lay in a trance for three days might help to explain some miracles； like the raising of Lazarus。 His great work was Conciliator Differentiarum； an attempt to reconcile physicians and philosophers。 But his researches were not confined to medicine； for he seems to have had an inkling of the hitherto unknown fact that air possesses weight； and his calculation of the length of the year at three hundred and sixty…five days； six hours； and four minutes； is exceptionally accurate for the age in which he lived。 He was probably the first of the Western writers to teach that the brain is the source of the nerves； and the heart the source of the vessels。 From this it is seen that he was groping in the direction of an explanation of the circulation of the blood； as demonstrated by Harvey three centuries later。 The work of Arnald and Peter of Abano in 〃reviving〃 medicine was continued actively by Mondino （1276…1326） of Bologna； the 〃restorer of anatomy；〃 and by Guy of Chauliac： （born about 1300）； the 〃restorer of surgery。〃 All through the early Middle Ages dissections