In pursuing his studies at this favoured abode of science and literature, young Jackson is said to have evinced all that purity of morals and singleness of heart which characterised him in after-life, and to have resisted the allurements of dissipation by which, in those days especially, the youthful student was tempted to wander from the paths of virtuous industry. His circumstances were, however, distressingly narrow; and not only was he forced to forego the means of professional improvement open only to the more opulent student; but in order to meet the expenses of the winter-sessions, he was obliged to employ the summer, not in the study but in the practice of his profession. He engaged himself as medical officer to a Greenland whaler, and in two successive summers visited, in that capacity, 'the thrilling regions of thick-ribbed ice;' returning on each occasion with a recruited purse and a frame strengthened and invigorated by exposure and exercise. During these expeditions he occupied his leisure with the study of the Greek and Roman languages, and the careful and repeated perusal of the best authors in both.
His third winter-sessions at Edinburgh having passed away, he was induced to go out and seek his fortune in Jamaica, and accordingly proceeded thither in a vessel commanded by one Captain Cunningham, who had previously been employed as master of a transport at the siege of Havannah. It is far from improbable that it was from his conversations with this individual that Jackson derived those hints, of which at a future time he availed himself, respecting the transmission of troops by sea without injury to their health; but it is quite certain his conviction of the enormous value of cold-water affusions as a curative agent in the last stage of febrile affections, was imbibed from this source.
Arriving in Jamaica, he in 1774 became assistant to an eminent general practitioner at Savana-la-Mar, Dr King, who was also in medical charge of a detachment of the first battalion of the 60th regiment. This latter he consigned to Jackson's care; and well worthy of the trust did our young adventurer, though but twenty-four years of age, approve himself—visiting three or four times a day the quarters of the troops to detect incipient disease, and studying with ardour and intelligent attention the varied phenomena of tropical maladies. Four years thus passed profitably away, and they would have been as pleasant as profitable, but for one circumstance. The existence of slavery and its concomitant horrors appears to have made a deep impression on Jackson's mind, and, at last, to have produced in him such sentiments of disgust and abhorrence, that he resolved on quitting the island altogether, and, as the phrase is, trying his luck in North America, where the revolutionary war was then raging. This resolution—due perhaps, as much to his love of travel as to the motive assigned—was not altogether unfortunate, for shortly after his departure, October 3, 1780, Savana-la-Mar was totally destroyed, and the surrounding country for a considerable distance desolated, by a terrible hurricane and sweeping inroad of the sea, in which Dr King, his family and partner, together with numbers of others, unhappily perished.
The law of Jamaica forbade any one to leave the island without having given previous notice of his intention, or having obtained the bond of some respectable person as security for such debts as he might have outstanding. Jackson, when he embarked for America, had no debts whatever, and was, moreover, ignorant of the law, with whose requirements therefore he did not comply. Nor did he become aware of his mistake until, when off the easternmost point of the island, the master of the vessel approached him and said: 'We are now, sir, off Point-Morant; you will therefore have the goodness to favour me with your security-bond. It is a mere legal form, but we are obliged to respect it.' Finding this 'legal form' had not been complied with, the master then, in spite of Jackson's protestations and entreaties, set him on shore, and the vessel continued on her voyage. What was to be done? Almost penniless, landed on a part of the coast where he knew not a soul, Jackson well-nigh gave himself up to despair. There was a vessel for New York loading, it was true, at Lucea; but Lucea was 150 miles distant, on the westernmost side of the island, and not to be reached by sea, whilst our adventurer's purse would not suffer him to hire a horse. No choice was left him but to walk, and that in a country where the exigencies of the climate make pedestrianism perilous in the extreme to the white man. Having reached Kingston, which was in the neighbourhood, in a boat, and obtained the necessary certificate, he started on his dangerous expedition, and on the first day walked eighteen miles, being sheltered at night in the house of a benevolent planter. The next day he pushed on for Rio Bueno, which he had almost reached, when, overcome by thirst, he stopped by the way to refresh himself, and imprudently standing in an open piazza exposed to a smart easterly breeze, whilst his lemonade was preparing, contracted a severe chill that almost took from him the power of motion, and left him to crawl along the road slowly and with pain, until he reached his destination.
Having finally arrived, friendless and moneyless, in New York, then in the occupation of the British, he endeavoured first to obtain a commission in the New York volunteers, and afterwards employment as mate in the Naval Hospital. In his endeavours, he was kindly assisted by a Jamaica gentleman, a fellow-passenger, whose regard during the voyage he had succeeded in conciliating by his amiable manners and evident abilities; but his efforts were all in vain, and poor Jackson, familiar with poverty from childhood, began now to experience the misery of destitution. In truth, starvation stared him in the face, and a sense of delicacy withheld him from seeking from his Jamaica friend the most trifling pecuniary assistance. In this, his state of desperation, he determined upon passing the British lines, and endeavouring to obtain amongst the insurgents the food he had hitherto sought in vain; resolving, however, under no circumstances to bear arms against his native country. Whilst moodily and slowly walking towards the British outposts to carry into execution this scheme, having in one pocket a shirt, and in another a Greek Testament and a Homer, he was met half-way by a British officer, who fixed his eyes steadily on him in passing. Jackson in his agitation thought he read in the glance a knowledge of his purpose and a disapprobation of it. Struck by the incident, he turned back, and, after a moment's reflection, resolved on offering himself as a volunteer in the first battalion of the 71st regiment (Sutherland Highlanders), then in cantonment near New York. Arriving at the place, he presented himself to the notice of Lieutenant-Colonel (afterwards Sir Archibald) Campbell, who, having first ascertained that he was a Scotsman, inquired to whom he was known at New York. Jackson replied, to no one; but that a fellow-passenger from Jamaica would readily testify to his being a gentleman. 'I require no testimony to your being a gentleman,' returned the kind-hearted colonel. 'Your countenance and address satisfy me on that head. I will receive you into the regiment with pleasure; but then I have to inform you, Mr Jackson, that there are seventeen on the list before you, who are of course entitled to prior promotion.' The next day, at the instance of Colonel Campbell, the regimental-surgeon, Dr Stuart, appointed Jackson acting hospital or surgeon's mate—a rank now happily abolished in the British army; for those who filled it, whatever might be their competency or skill, were accounted and treated no better than drudges. Although discharging the duties that now devolve on the assistant-surgeon, they were not, like him, commissioned, but only warrant-officers, and therefore had no title to half-pay.
Dr Stuart, who appears to have been a man superior to vulgar prejudice, and to have appreciated at once the extent of Jackson's acquirements and the vigour of his intellect, relinquished to him, almost without control, the charge of the regimental hospital. Here it was that this able young officer began to put in practice that amended system of army medical treatment which since his time, but in conformity with his teachings, has been so successfully carried out as to reduce the mortality amongst our soldiery from what it formerly was—something like 15 per cent.—to what it is now, about 2½ per cent.
In the army hospitals, at the period Jackson commenced a career that was to eventuate so gloriously, there was no regulated system of diet, no classification of the sick. What are now well known as 'medical comforts,' were things unheard of; the sick soldier, like the healthy soldier, had his ration of salt-beef or pork, and his allowance of rum. The hospital furnished him with no bedding; he must bring his own blanket. Any place would do for an hospital. That in which Jackson began his labours had originally been a commissary's store; but happily its roof was water-tight—an unusual occurrence—and its site being in close proximity to a wood, our active surgeon's mate managed, by the aid of a common fatigue party, to surround the walls with wicker-work platforms, which served the patients as tolerably comfortable couches. A further and still more important change he effected related to the article of diet. He suggested, and the suggestion was adopted—honour to the courageous humanity which did not shrink from so righteous an innovation!—that instead of his salt ration and spirits, which he could not consume, the sick soldier should be supplied with fresh meat, broth, &c.; and that, as the quantity required for the invalid would be necessarily small, the quarter-master should allow the saving on the commuted ration to be expended in the common market on other comforts, such as sago, &c. suitable for the patient. Thus proper hospital diet was furnished, without entailing any additional expense on the state.[2]
Indefatigable in the discharge of his interesting duties, Mr Jackson speedily obtained the confidence of his military superiors, who remarked with admiration not only his intelligent zeal in performing his hospital functions, but his calmness, quickness of perception, and generous self-devotion when in the field of battle. On one occasion, although suffering at the time from severe indisposition, he remained, under a heavy fire, succouring the wounded, in spite of the remonstrances of the officers present. On another, having observed the British commander, Colonel (afterwards General) Tarleton, in danger of falling into the hands of the enemy, who had routed the royalist troops, he galloped up to the colonel—whom a musket-ball had just dismounted—pressed him to mount his own horse and escape, whilst he himself, with a white handkerchief displayed, quietly proceeded in the direction of the advancing foe, and surrendered himself at once. The American commander, who did not know what to make of such conduct, asked him who he was? He replied: 'I am assistant-surgeon in the 71st regiment. Many of the men are wounded, and in your hands. I come, therefore, to offer my services in attending them.' He was accordingly sent to the rear as a prisoner; but was well treated, and spent the first night of his captivity in dressing his soldiers' wounds, taking off his shirt, and tearing it up into bandages for the purpose. He afterwards did the same good office for the American sufferers; and when the wounded English could be exchanged, Washington sent him back, not only without exchange, but even without requiring his parole. At a subsequent period during the same unhappy war, when the British under Lord Cornwallis were in full retreat, the sick and wounded were placed in a building which the colonists, on their approach, began to riddle with shot. Several surgeons, not caring to incur the risk of entering so exposed an edifice, agreed to cast lots who should go in and see to the invalids; but Jackson, with characteristic nerve and simplicity, at once stepped forward: 'No, no,' said he, 'I will go and attend to the men!' He did so, and returned unhurt.
After this we find him a prisoner in the hands of the Americans and French at New York Town, Virginia. As on the former occasion, he was treated with all imaginable kindness; and, being released on parole, returned to Europe early in 1782, and proceeded by way of Cork, Dublin, and Greenock to Edinburgh, where he abode for a short time. Thence he started for London; and, desirous of testing the best way of sustaining physical strength during long marches, and urged perhaps also by economical considerations, he resolved to make the journey on foot. His West Indian and American experience had taught him that spare diet consisted best with pedestrian efficiency, and it was accordingly his practice, during this long walk, to abstain from animal food until the close of day, nor often then to partake of it. He would walk some fourteen miles before breakfast—a meal of tea and bread; rest then for an hour or an hour and a half; then pace on until bedtime—a salad, a tart, or sometimes tea and bread, forming his usual evening fare. He found that on this diet he arose every morning at dawn with alacrity, and could prosecute without inconvenience his laborious undertaking. By way of experiment he twice or thrice varied his plan—dining on the road off beefsteaks, and having a draught of porter in the course of the afternoon; but the result justified his anticipations. The stimulus of the beer soon passing off, lassitude succeeded the temporary strength it had lent him; and, worse than all, his disposition to early rising sensibly diminished.
His stay in London, which he reached in this primitive fashion, was not long. His kind friend Dr Stuart, who had exchanged into the Royal Horse-Guards, gave him the shelter of his roof; but so poor was Mr Jackson, that, although ardently desirous of improving himself in his profession, he was unable to attend any one of the medical schools with which London abounds.