I

O'Halloran's first publications related to the eye, specifically the treatment of cataract. In the mid eighteenth century the standard operation for cataract was ‘couching’ (from coucher, to lay down), whereby the crystalline lens in the eye was dislocated out of the line of vision either by the application of blunt force to the eyeball or the insertion of a sharp instrument into the eye. The displaced lens remained within the eye. Thus, light would pass again to the retina, but without spectacles sight would not be much improved.Footnote ²² Published in 1750, O'Halloran's A new treatise on the glaucoma or cataract is a wordy dissertation on many topics relating to the eye. He provided a summary of seventeen ‘discoveries made by the author’.Footnote ²³ His conclusions were based on wide reading of the medical literature, as well as anatomical dissections and vivisection experiments on live dogs.Footnote ²⁴ One of his principal conclusions was to confirm that the opacity in a cataract is located in the lens, a fact discovered by French surgeons in the early 1700s.Footnote ²⁵

O'Halloran also discussed glaucoma, now known to be a group of diseases characterised by an accumulation of aqueous humour in the eye that leads to high intraocular pressure, damage to the optic nerve and blindness.Footnote ²⁶ Eighteenth-century oculists observed that while cataracts produced a white or yellowish opacity in the eye, glaucoma was associated with a ‘glaucous’ (light blue, grey or green) pupil.Footnote ²⁷ O'Halloran observed: ‘tho all agree to the existence of a glaucoma, or incurable cataract, yet they are far from agreeing to its seat.’Footnote ²⁸ He concluded incorrectly that cataract and glaucoma were one and the same disease.Footnote ²⁹ Other deductions were that there are no connections between the ciliary body and the lens, and that ‘there is not any circulation of the humours in the eye’: both of these were wrong.Footnote ³⁰ To improve the couching operation he proposed ‘by force of arguments’ that if some method could be devised to ‘take away’ the capsule of the lens as well as the opacity in the lens ‘we should see pretty nigh as well after the operation as if no such disorder had ever happened’.Footnote ³¹ He seems to have been unaware of the pioneering work on lens extraction for cataract published by Jaques Daviel (1696–1762) in Paris in 1748, but his idea almost anticipated Samuel Sharp's (1709–78) and George de la Faye's (1699–1781) influential ‘intracapsular’ operations in which the lens and capsule were extracted from the eye.Footnote ³²

On 8 April 1747 Jacques Daviel revolutionised cataract surgery by removing the lens containing a cataract from the eye of a Parisienne wigmaker, M. Garion, through a large incision in the cornea.Footnote ³³ He described and illustrated his operation in letters to Mercure de France in 1748 and to the Académie Royale de Chirurgie in 1753, claiming that of 206 procedures ‘182 have succeeded’.Footnote ³⁴ In two letters to the Royal Society in London in 1752 Dr Thomas Hope provided the first eye-witness descriptions of Daviel's operation in English.Footnote ³⁵ It is likely that O'Halloran became aware of the procedure from these letters, which sparked a debate at the Royal Society. ‘At the instigation of a couple of learned friends’, O'Halloran contributed to the debate quoting extensively from his own work.Footnote ³⁶ In passing, he disparaged the eminent English surgeon William Cheselden (1688–1752), saying that he ‘knew very little of the structure of the eye, not to mention that his figures of the eyes are very erroneous’.Footnote ³⁷ What the members of the Royal Society thought of the young Irish surgeon's opinions is unknown, but he himself stated that he ‘had the satisfaction to find them well received’.Footnote ³⁸ In April 1753 Samuel Sharp, from Guy's Hospital, informed the Royal Society of his new cataract operation. Having incised the cornea transversely with a sharp knife, he removed the lens and capsule by pressing on the eyeball. Later he used the point of a knife to extract the lens cleanly and provided details of eleven cases.Footnote ³⁹ Concurrently in France, George de la Faye described a very similar operation.Footnote ⁴⁰ These various operations became the standard treatments for cataract for the next two hundred years.Footnote ⁴¹

Stimulated by Daviel's work, O'Halloran began a series of experiments culminating in the publication of his second book, A critical analysis of the new operation for a cataract, in 1755. O'Halloran declared that although Daviel's operation had many advantages ‘it is not without its faults, nor to be attempted indiscriminately in all cases’.Footnote ⁴² Unacquainted with Daviel's published accounts in French, he stated that Daviel had ‘never favoured the publick with a particular detail of his method’. He dismissed Dr Hope's very clear, accurate and concise description of the procedure to the Royal Society as being ‘from a spectator only’. O'Halloran began to practise Daviel's operation on sheep's heads and live dogs before attempting it in a patient.Footnote ⁴³ He noted that the discomfort of opening the cornea was insignificant but ‘people err greatly who imagine it to be attended with no pain’.Footnote ⁴⁴ He was dismissive of the operation saying that it had not met with great success in either London or Dublin. This was also his own experience, but he gave no details. Having discussed various instruments that might be used for the operation, he offered a theoretical improvement suggesting that the lens be approached through the sclera and not the cornea, but ‘for want of time’ he had not tried it or performed any experiments.Footnote ⁴⁵ In 1757 he informed the Dublin Medico-Philosophical Society by letter that he had successfully performed Daviel's operation.Footnote ⁴⁶

O'Halloran's final reflections on cataract came years later in 1788 in a paper to the newly formed Royal Irish Academy. He revisited the anatomy of the eye and discussed the methods for cataract extraction including those of Daviel, Sharp and de la Faye. His conclusion ‘from sound practice’ was: ‘never was operation less entitled to public estimation.’ He offered his own novel technique of incising the ‘sclerotica’ with a special pointed double-edged knife that he had designed. By gentle pressure on the eye ‘the cataract will instantly slip out’ the advantage being ‘very little if any opacity’ on the cornea’. While he gave no details of individual cases or numbers treated, O'Halloran must be acknowledged for designing and procuring instruments to facilitate a reduction in the incidence of corneal opacity. However, his ideas were not adopted by his contemporaries.Footnote ⁴⁷

II

The second medical topic that interested Sylvester O'Halloran was limb amputation, which he discussed in two publications in 1763 and 1765.Footnote ⁴⁸ Limb amputation in the eighteenth century was a grim affair with speed being of the essence. The two major complications were secondary haemorrhage from ligature failure and poor wound healing from infection.Footnote ⁴⁹ Earlier surgeons divided the skin, muscle, and bone at the same level — the ‘one-stage circular cut’ — but problems with wound healing induced later surgeons to cut the skin and muscle at a lower level than the bone — the ‘two stage circular cut’.Footnote ⁵⁰ From the 1670s some surgeons fashioned a flap of skin and muscle to cover the end of the bone to allow for better wound healing.Footnote ⁵¹ As long as an infection or a haemorrhage did not ensue the wound healed well ‘by first intention’; if an infection occurred the wound would open and slowly heal ‘by second intention’ with scarring over the end of the stump. O'Halloran argued that immediate closure of the flap would always end in disaster and advocated delayed closure of the wound at about ten days; ‘inflammation and suppuration are absolutely necessary to bring on a reunion of divided parts’.Footnote ⁵² He got his novel idea following a mastectomy when he packed the open wound with lint and flour, and kept it open until the ninth day after the operation; ‘to the surprise of all her acquaintance, she was cured’.Footnote ⁵³ This then was his ‘new method’ — separation of the flap from the bone for several days until the infection had occurred and subsided.

In the short monograph A concise and impartial account, he presented two cases of amputation by his new method. Francis Kennelly had a below-knee amputation on 27 November 1761 for chronic disease of the bones around the ankle. A haemorrhage on the fifth postoperative day was easily controlled by the application of Lycoperdon, a puff-ball fungus with known coagulant properties.Footnote ⁵⁴ The wound was closed on day twelve and by day fourteen the stump was covered ‘by a cushion of flesh and skin … and the sore reduced to a superficial one’. Alice Blachall, aged fifteen, had her leg amputated on 23 July 1762. The flap and stump were not united until day twelve but did not fuse properly until day twenty-eight; she was discharged ‘completely cured’.Footnote ⁵⁵ He had four of his medical colleagues attest to the success of the two operations. They concluded: ‘we are persuaded that, were this method more universally known and practised, it would be rendering to the community and to mankind, a most essential service.’ To clinch the evidence, the mayor and sheriffs of Limerick City examined Kennelly and declared that he could now walk on his stump, as could Alice Blachall. Alice died in hospital five months later from smallpox. In the presence of witnesses, including two regimental surgeons, O'Halloran dissected her leg and found that her amputation wound had healed and the flap adhered strongly to the bones.Footnote ⁵⁶

In the larger work entitled A complete treatise on gangrene and sphacelus, O Halloran defined gangrene as severe tissue damage or ‘tendency to mortification which often gives way to remedies’, while ‘sphacelus’ equated to the modern concept of gangrene, that is dead tissue that ‘can only be remedied by amputation’.Footnote ⁵⁷ ‘Flux of humours to the part’ and inflammation of the blood caused ‘internal gangrene’ while frost, gunshot wounds and compound fractures caused ‘external gangrene’.Footnote ⁵⁸ O'Halloran cautioned against immediate amputation in the latter.Footnote ⁵⁹ Having reviewed the history of amputation he described his method for amputation in the thigh, leg and arm. He presented fifty-eight case histories, a mixture of patients who had a wide range of problems including infections, tumours, fractures, and various wounds. Of these, twelve died while thirteen underwent an amputation. In only three of his patients did he use his new method and two were the patients he had already described in his earlier publication; the third had an arm amputated with a good outcome.Footnote ⁶⁰ However, in 1793 in a letter to Edmund Burke he stated that he had performed fourteen amputations in Limerick using his new method. The operation was not taken up by others. In an open letter to the surgeons of Dublin in January 1772 he complained: ‘the surprise will be that so important a discovery should be so long overlooked … why will you not adopt it?’Footnote ⁶¹ It is likely that they did not think his new method was a particularly good idea. In 1782 Edward Alanson, surgeon to the Liverpool Infirmary, commenting on O'Halloran's method, defended primary closure of the wound:

Alanson provided data. Of forty-six patients who had a traditional two-stage circular cut amputation ten died, eighteen had a haemorrhage and most developed ‘suppuration’.Footnote ⁶³ In contrast, thirty-six patients who had primary closure of the wound using a flap, all survived, and none had a haemorrhage or serious infection.Footnote ⁶⁴ In modern surgery primary closure with a flap is the standard technique for major limb amputation.Footnote ⁶⁵ Nonetheless, despite his colleagues’ reluctance to endorse his method, O'Halloran felt that he was entitled to a ‘national reward’ for devising this amputation which ‘in any country of Europe … would not be unnoticed!’ and repeated this view in letters to Edmund Burke seeking, unsuccessfully, a civil-list pension in recognition of his work in 1793.Footnote ⁶⁶

III

The third medical subject that Sylvester O'Halloran dealt with was the management of traumatic brain injury, a problem he encountered frequently. In the early 1790s he published a short paper, ‘An attempt to determine with precision such injuries of the head as necessarily require the operation of the trephine’.Footnote ⁶⁷ In this he presented twelve case histories to support his proposition that many head injuries did not require trephination. Subsequently, in 1793, he published A new treatise on the different disorders arising from external injuries of the head illustrated by eighty-five selected from above fifteen hundred practical cases, where he expanded on his earlier ideas.Footnote ⁶⁸ The understanding of head injury changed little from classical times to the early eighteenth century when it was still believed that symptoms arose from injury to the bone and meninges rather than the brain.Footnote ⁶⁹ The Dublin surgeon, William Dease (1752‒98), wrote of earlier authors: ‘the symptoms which we annex to concussions of the brain, they in general attributed to the injury the bone received.’Footnote ⁷⁰ Henri-Francois Le Dran (1685‒1770) was the first to correctly identify the brain as the source of post-traumatic head injury problems.Footnote ⁷¹ O'Halloran agreed but, harkening back to classical humoral medicine, he believed that the animal and vital spirits were situated in the brain stem, which he described as ‘the primary seat of the soul’.Footnote ⁷² In his view, disruption of this area caused post-traumatic symptoms but because of its deep position within the skull it was not amenable to trephination.Footnote ⁷³

From prehistoric times making a hole in the skull was a frequent treatment for head injury, ‘madness’ and epilepsy.Footnote ⁷⁴ In the eighteenth century opening the skull using a trepan or trephine facilitated the lifting of depressed fractures and removing blood clots or other debris from the surface of the brain.Footnote ⁷⁵ However, because of high mortality rates, often from infection, there was considerable debate whether trepanation should be undertaken at all. The English surgeon Percivall Pott (1713–88) was an ardent advocate of early trepanation in all skull fractures, while Jean-Louis Petit (1674–1750) adopted the more conservative approach favoured in France.Footnote ⁷⁶ O'Halloran was firmly in the conservative camp: ‘I consider the operation of the trepan as very cruel, a painful and a dangerous one; nor to be attempted without the clearest evidences of its necessity.’Footnote ⁷⁷ He based his conclusions on numerous cases he had treated personally, citing whiskey-fuelled faction fighting as the cause of the many head injuries seen in Ireland at the time. Not without justification, he considered himself to be ‘a master’ in the management of head trauma.Footnote ⁷⁸ In his initial paper O'Halloran succinctly summarised the indications for and against trepanation after head trauma. He concluded that many fractured skulls and those presenting with concussion — ‘immediate stupor and insensibility’ — did not require trepanation.Footnote ⁷⁹ Depressed fractures or the presence of matter on the surface of the brain ‘absolutely require its application’ as did apparently slight fractures that developed bad symptoms a fortnight or so after the injury. O'Halloran's conclusions anticipated modern neurosurgery where only a minority of head injuries require craniotomy and for very specific indications. O'Halloran's second publication expanded on the earlier work adding sections on the pathology of head injury, the nature of concussion, hydrocephalus and the formation of matter on the brain. He restated his warnings against the indiscriminate use of the trephine, asking ‘Is an operation of this consequence, infinitely more severe and violent than the cause that gave rise to it, to be wantonly or capriciously attempted?’Footnote ⁸⁰ His reply was an emphatic ‘no’.

How O'Halloran recorded the details of his cases is unknown. He may have kept a case or fee book or documented only certain cases that interested him. Presumably, details of patients admitted to the Limerick County Infirmary would have been recorded but only nineteen of the eighty-five patients described were treated there, the others in private houses. Twenty-nine of his patients died, a mortality rate of 34 per cent, which compared favourably with other known eighteenth-century mortality rates.Footnote ⁸¹ O'Halloran's books also open a window on life in eighteenth-century Ireland. He treated patients from all levels of society. All but eight of his head injury patients were male and eight were children. The youngest was fifteen-months-old — a child with hydrocephalus, which he correctly deduced proceeds ‘from some defect in the organization of the parts as yet unknown, or from the secretions not being properly conducted’.Footnote ⁸² Forty-three people had been victims of assault, twenty-two were thrown from or kicked by horses, while eleven fell from a height. Although he wrote of ‘the frequent abuse of spirituous liquors’ as the cause of ‘bloody conflicts’ at ‘fairs, patrons and hurling matches’, he recorded alcohol as a contributing factor to head injury in only ten of his patients.Footnote ⁸³ Following their head injuries most of the patients had been attended immediately by a friend or another medical professional. Bloodletting, blistering and a variety of herbal concoctions were administered and then ‘an express’ was sent to summon O'Halloran. On arrival and in consultation with any doctors present he would explore the head wound and decide whether trepanation was indicated or not. Occasionally he was dissuaded from operating in case the patient's death ‘might be charged to the operation, not to the injury’.Footnote ⁸⁴ Overall, he trepanned thirty-one patients, mostly for depressed fractures of the skull, of whom twenty-one recovered. With the consent of the relatives, he frequently performed post-mortem examinations on those that died to determine the nature of the fatal head injury.

IV

O'Halloran played a pivotal role in developing surgical care in Limerick and in professionalising surgery in Ireland. In 1759, concerned at the lack of a hospital in Limerick, O'Halloran and another surgeon, Giles Vandeleur, rented three small houses which ‘they threw into one and opened four beds’.Footnote ⁸⁵ After a year the hospital charity failed due to the death of Vandeleur and lack of support, but O'Halloran and others revived it with a benefit play in early 1761. As subscriptions increased more beds were opened and a project begun to build a new hospital. On 19 March 1765 Edmond Sexton Pery, M.P. for Limerick City, donated a piece of ground in the old St Francis's Abbey outside the city walls for a hospital at a peppercorn rent in perpetuity. The site contained the shell of a building which ‘was rebuilt and is now capable of receiving upwards of forty beds’. In its first twenty years the hospital received £10,375 18s. 6½d. in subscriptions and treated 5,003 in-patients and 54,148 outpatients, of whom 29,428 were cured.Footnote ⁸⁶ As the hospital was in the county, the governors, including O'Halloran, resolved in 1766 that it be designated the County of Limerick Infirmary pursuant to the recently enacted County Infirmaries Act (1766). John Martin and John Barret were appointed as physicians and ‘Messrs. O'Halloran, Mahony and Knight … attending surgeons in yearly rotation’.Footnote ⁸⁷ As a county infirmary the hospital received funding from parliament and the Limerick county grand jury, thus securing its future.Footnote ⁸⁸

O'Halloran would be associated with the hospital for the rest of his life. The Medical Review of 1775 noted:

In 1778 the hospital was criticised in an Irish House of Commons report for being ‘very dirty… all confusion, no regulation…full of smoke’, but ten years later John Howard was pleasantly surprised to find it ‘thoroughly repaired, white-washed and furnished with new bedding’.Footnote ⁹⁰ These changes he ascribed to the efforts of Lady Hartstonge and a new matron rather than O'Halloran. However, O'Halloran was remembered in Limerick as ‘a man of wonderful ability…turning out every day very responsibly to visit his patients’.Footnote ⁹¹

As the new hospital was getting off the ground O'Halloran turned his attention to the training of surgeons in Ireland. Having observed the highly structured system of training in France compared to the lax apprenticeship approach in Ireland, he published Proposals for the advancement of surgery in Ireland as an appendix to A complete treatise.Footnote ⁹² In France prospective surgeons had to possess a master of arts degree from a university, go through ‘a painful course of studies’ and pass ‘a severe course of examinations’ conducted by the ‘first men of the profession’ under the auspices of the Académie Royale de Chirurgie. Candidates were required to be proficient in anatomy and surgery, and the performance of ‘all the operations of surgery on a body’. In contrast in Ireland ‘the most ignorant impostor had as much right to trade in human flesh as the first surgeon.Footnote ⁹³ O'Halloran proposed the establishment of a system similar to that in France, effectively the creation of an Irish college of surgeons. He recommended that a suitable ‘edifice’ be built for surgeons in Dublin, that three professorships in anatomy, surgery and midwifery be created, that a series of lectures and examinations be established free of fee to the candidate, and that only surgeons listed in an annual register be allowed practise surgery.Footnote ⁹⁴

While no corroborating evidence exists, O'Halloran certainly believed that his Proposals influenced the Irish parliament in 1766 in their creation of the County Infirmaries Board as part of the County Infirmaries Act.Footnote ⁹⁵ In his journal he wrote: ‘In 1765 published my “Treatise on Gangrene” the appendix to which gave rise to the Infirmary Act, the most useful in its way.’Footnote ⁹⁶ In March 1766, a month before the infirmary bill was presented to parliament O'Halloran received from his friend and one of the sponsors of the bill, Dr Charles Lucas, a ‘very long and polite letter to bestow many encomiums on my work’.Footnote ⁹⁷ While the contents of the letter are unknown it is likely that Lucas was aware of his friend's proposals for regulating surgery and incorporated some of the ideas into the bill. The County Infirmary Board was not a college, but a panel of assessors that examined in anatomy and surgery all surgeons being appointed to the new county infirmaries, including O'Halloran.Footnote ⁹⁸ It marked the beginning of an identifiable surgical profession in Ireland.Footnote ⁹⁹ With an alternative method of professional assessment available, few surgeons now joined the guilds of barber-surgeons whom they regarded as their inferiors.Footnote ¹⁰⁰ The practising surgeons sought to come together as a group and to dissociate themselves completely from the ‘preposterous and disgraceful union’ with the barbers. In March 1780 the Dublin Society of Surgeons was established which, four years later, was successful in its petition to government to establish a college of surgeons to regulate the profession and put in place a system of training for surgeons.Footnote ¹⁰¹ O'Halloran was elected an honorary member of the society in October 1780 and of the Royal College of Surgeons in 1786.Footnote ¹⁰²

Although the evidence is conjectural, O'Halloran's proposals seem to have been the blue-print for the educational system put in place by the new college; the similarities between his proposals and the system established are striking.Footnote ¹⁰³ Professors were appointed to give lectures in anatomy, physiology and surgery, and candidates were examined in these and surgical pharmacy. O'Halloran's suggestion that the candidates should perform ‘all the operations of surgery on a body, with their apparatus and bandaging’ was not taken up, perhaps because of the difficulty in obtaining cadavers or a suitable premises where dissection might be performed.Footnote ¹⁰⁴ His suggestion that that there be no expense to the candidate was also ignored and fees of ten and twenty guineas were levelled for letters testimonial and membership, respectively. Licences in midwifery could also be awarded (to men) for ten guineas.Footnote ¹⁰⁵ The surgeons had to wait until 1810 to occupy a ‘suitable edifice’, Surgeons Hall on St Stephen's Green.Footnote ¹⁰⁶ The unique proposal that a list of reputable surgeons be maintained was not achieved until 2007, when surgeons were included in the specialist division of the register of Irish medical practitioners.Footnote ¹⁰⁷ The close resemblance between O'Halloran's proposals and the new college curriculum, as well as the honour in which he was held by the Dublin surgeons, makes it very likely that his ideas on education inspired them to adopt a system of training and examination analogous to what he had proposed in 1765.Footnote ¹⁰⁸

V

Sylvester O'Halloran's style of writing was mostly verbose with many digressions from his subject. For example, in A new treatise he provides an amusing description of the rituals performed by the famous itinerant oculist, Chevalier John Taylor, prior to couching,Footnote ¹⁰⁹ while his Proposals include an attack on David Hume for his opinions about the Irish nation.Footnote ¹¹⁰ He illustrated his later works with case histories but, excepting head injury, many of the cases had little to do with the topic under review. Moreover, the same cases were often recycled in later publications. However, he was capable of brevity. A concise and impartial account is a short work of twenty pages that provides specific clinical details of his new amputation method;Footnote ¹¹¹ similarly, the précis of his Proposals is a model of brevity.Footnote ¹¹² In ‘An attempt to determine with precision’ he achieved his aim of being ‘as clear and concise as possible’ with regard to trepanation following head trauma.Footnote ¹¹³ The audience O'Halloran had in mind for his work is difficult to discern given that his books were highly technical and probably only of interest to a small cadre of practising surgeons. However, he did have an international medical reputation with his work receiving recognition in England and France.Footnote ¹¹⁴

O'Halloran inscribed his monographs to a variety of people. A new treatise was dedicated to Dr Richard Mead (1673–1754), ‘the Hippocrates of the present age,’ who deemed it ‘not unworthy of public notice’.Footnote ¹¹⁵ Thus encouraged, O'Halloran sent it to Dr Edward Barry (1698–1776), president of the Royal College of Physicians of Ireland, hoping that they would approve his work and ‘make the world look with more deference’ on his treatise, and presumably also on him.Footnote ¹¹⁶ There is no record of the monograph and no mention of O'Halloran in the archives of the Royal College of Physicians, but he recounts that they showed no interest in his work and declined to approve it.Footnote ¹¹⁷ Their lack of enthusiasm is perhaps not surprising. O'Halloran was a young unknown Catholic surgeon without a medical degree from a small provincial centre who had trained in France.Footnote ¹¹⁸ The fellows of the Royal College were all prominent Protestant physicians who would have had little interest in surgical matters or in studying a longwinded surgical text. Prior to the founding of the Irish College of Surgeons in 1784 physicians and surgeons rarely met in consultation and a proposal that they might was ignored by the physicians in 1785.Footnote ¹¹⁹ Surprisingly, in 1755 O'Halloran again dedicated his second book, A critical analysis, to Dr Barry. As a fellow of the Royal Society, Barry may have facilitated O'Halloran's presentation to the society in 1753. Why Barry changed his attitude is unclear. O'Halloran believed that Barry had allowed his name to appear on the presumption that the book might be useful to the public.Footnote ¹²⁰ Barry was at the height of his career; his expertise was in treating tuberculosis and as a physician he would never perform cataract surgery.Footnote ¹²¹ He may have appreciated the importance of Daviel's novel operation in extracting rather than couching cataracts and was happy to promote this new treatment through O'Halloran's monograph.

In 1763 O'Halloran dedicated his introductory work on amputation, A concise and impartial account, to several people: Ezekiel Nesbit, president of the College of Physicians; the censors and fellows of the college; John Nichols, the surgeon general, and the ‘very Respectable Body of Surgeons of said city’.Footnote ¹²² It is understandable that he mentioned surgeons who might adopt his technique but not so obvious as to why he included fellows of the college of physicians, other than the hope of being acknowledged by the medical establishment. Two years later O'Halloran dedicated his substantial 289-page monograph, A complete treatise on gangrene and sphacelus to Francis Seymour-Conway (1714–94), lord lieutenant of Ireland, hoping that his influence might have it adopted for ‘general use in the military hospitals of this kingdom’.Footnote ¹²³ Uniquely, he inscribed fifteen of the nineteen chapters in the book to various individuals: six leading medical men, eight prominent locals from Limerick and Clare, and the Dublin Society. Given his later grumbling that he deserved a ‘national reward’ for his new amputation technique, it likely that he dedicated the various chapters to those whom he thought might support his application for a state pension.Footnote ¹²⁴ His last major medical treatise on head injuries, published in 1793, was not dedicated to anyone. Having by then attained prominence as a surgeon and historian, he perhaps felt no further need to flatter the establishment.

O'Halloran's theoretical understanding of medicine was rooted in the humoral ideas of classical and medieval medicine.Footnote ¹²⁵ Thus, in relation to gangrene he referred to ‘a sharp humour’ forming ‘which will ‘gradually consume muscles, ligaments, blood vessels and bones’.Footnote ¹²⁶ The ‘fermentation of these humours forms pus’, giving rise to the ‘laudableness of suppuration’.Footnote ¹²⁷ O'Halloran also believed in the Galenic concept of ‘animal and vital spirits’ which he located in the brain stem.Footnote ¹²⁸ In contrast, in his practice he was forward thinking: he performed experiments, anatomical dissections and post-mortem examinations to discover the nature of disease and he seemingly kept detailed records of some individual patients treated. His clinical decisions were based on his experience rather than theoretical constructs, thus he advised caution when contemplating limb amputation and was categorical in his view that many head injuries did not require trepanation. So, while his theoretical understanding of medicine was backward-looking, his practice reflected a more modern scientific approach.

O'Halloran's medical publications had minimal impact on contemporary medical practice. His first publication, A new treatise, contained nothing new and many of his conclusions were inaccurate. Moreover, although he was in Paris at the time, he was unaware of Daviel's seminal work on cataract which had been published there in 1748. His second monograph published in 1755 offered a critique of Daviel's operation which he concluded was never performed ‘with success adequate to expectations’.Footnote ¹²⁹ He did not mention the important works of Sharp and de la Faye published two years earlier. Only in 1788 did he refer to Daviel, Sharp and de la Faye but was of the opinion that his own method of cataract extraction was better. In none of his writings on the eye did he give details of cases he had treated and his novel but technically difficult surgical approach to the lens via the sclera was ignored. However, his writings on the eye represented a significant body of academic work and scholarship, and he was the only one in Ireland to publish anything about the subject at the time. In his two monographs about limb amputation, he described fifty-eight patients but only three of them had undergone amputation by his new method. His belief that wounds always needed to suppurate before healing was seriously flawed and denied the possibility of primary wound closure as his contemporaries showed. Nonetheless, he believed he deserved official recognition and a pension for his innovation. Only his monograph on head injury was clinically important. He was clear that most head injuries other than depressed fractures did not need to be trepanned and his work contributed to the evolving management of head injury in the eighteenth century.Footnote ¹³⁰ Anticipating modern neurosurgical management, his conservative approach to traumatic brain injury avoided painful, unnecessary, and potentially fatal operations for many.Footnote ¹³¹

O'Halloran's greatest legacy was his influence on surgical training in Ireland. His Proposals were based on his knowledge of contemporary surgical training in France and were far ahead of what was current in Ireland or England at the time. While the evidence is circumstantial, his ideas possibly influenced legislators in 1766 in creating the County Infirmaries Board which was the first examining body for surgeons in Ireland. When the Royal College of Surgeons in Ireland was established in 1784 their curriculum adhered very closely to O'Halloran's proposals, and both the Society of Surgeons and the new college acknowledged him with honorary membership.

From O'Halloran's writings a strong, self-confident personality emerges, tinged with ‘a strong vein of conceit’.Footnote ¹³² Although from a small provincial city he was forthright in giving his opinions in his contributions to learned societies. Of the famous English surgeon John Hunter, he wrote: ‘I know him personally … considering his confined and narrow education, I should expect nothing very remarkable from him.’Footnote ¹³³ While he criticised renowned medical contemporaries such as William Cheselden, Pericval Pott and Jacques Daviel, he was easily affronted himself. The lack of engagement of the College of Physicians with his first monograph on cataract bothered him greatly. His belief that he should have a pension for his amputation technique demonstrates a lack of insight as does his incomprehension at the surgical community's indifference to his procedure. In his medical practice he was an excellent clinician whose opinion colleagues regularly deferred to and many correspondents sought his advice about personal medical problems.Footnote ¹³⁴ Once described as ‘a bit of a buzz-fuzz’Footnote ¹³⁵ O'Halloran must have seemed an eccentric character as he went about Limerick ‘with his cocked hat and ruffles’ and gold-headed cane. He was remembered as ‘a strange mixture of industry and carelessness’ but also of ‘wonderful ability’.Footnote ¹³⁶ His vivisection experiments suggest an element of callousness in his character. An unexpected pleasure is the glimpse his publications provide into eighteenth-century Irish social life, which emerges from the details of his patients. Despite his strongly-held views and many learned publications, Sylvester O'Halloran's impact on eighteenth-century medical practice was at best modest, but his ideas on education were pivotal in the evolution of professional surgical training in Ireland.Footnote ¹³⁷