On the war breaking out in 1793, Dr Jacksonwho, in 1791, had published a valuable work on the fevers of Jamaica and continental Americaapplied for employment as army-physician; but Mr Hunter, the director-general of the medical department of the army, considering none eligible for such employment who had not served as staffer regimental surgeon, or apothecary to the forces, Jackson agreed to accept, in the first instance, the surgeoncy of the 3d Buffs, on the understanding, that at a future time, he should be nominated physician as he desired. Mr Hunter, however, died soon after this; and his promise was not fulfilled by the Board which succeeded him in the medical direction of the army, and which appears to have pursued Dr Jackson with uniform hostility.
Returning to England with the troops, it was offered to him to accompany, in the capacity of chief medical officer, Sir Ralph Abercromby's expedition against some of the West India islands; and although no employment could possibly have been more agreeable to his taste, he, much to Sir Ralph's chagrin, declined the flattering proposal, on the grounds, that lower terms had been offered to him than to another professional man. Nothing but a sense of professional delicacy, it is plain, governed him in this transaction, for he immediately afterwards embarked (April 1796) as second medical officer in another expedition to San Domingo. During his abode in this island, he was unwearied in enlarging his acquaintance with tropical diseasesobserving the rule he had followed in Holland of noting down by the patient's bedside the minutest particulars of every case he attended, the effects of the treatment pursued, and whatever else might shed light on the intricacies of pathological science. He also gave a larger practical operation to the scheme he had years before devised of amending the dietaries of military hospitals.
After the evacuation of San Domingo in 1798, our physician paid a visit to the United States, where he was received with signal distinction, his reputation having preceded him. The latter part of the year found him again at Stockton, publishing a work on contagious and endemic fevers, 'more especially the contagious fever of ships, jails, and hospitals, vulgarly called the yellow-fever of the West Indies;' together with 'an explanation of military discipline and economy, with a scheme for the medical arrangements of armies.' He undertook, about this time, by desire of Count Woronzow, the Russian ambassador, the medical charge of seventeen hundred Russian soldiers, who were stationed in the Channel Islands in a sad state of disease and disorganization; and so admirably did he acquit himself, and so perfect were the hospital provisions he made, that (1800) the commander-in-chief nominated him physician and head of the army-hospital depôt at Chathamas he says, 'without any application or knowledge on his part.' This appointment was the cause of his subsequent misfortunes.
At Chatham, with the warm approbation of Major-General Hewett, commanding the depôt, he introduced that system of hospital reform which had elsewhere operated so successfully. The changes he effected, as soon as they were made, became known to the Medical Board, and were publicly approved of by one of its members. However, shortly afterwards, an epidemic broke out in the depôt (then removed to the Isle of Wight), arising from the fact, that the barracks were overcrowded with young recruits, but which the Medical Board ascribed to Jackson's innovations, and reported so to the Horse-Guards. The commander-in-chief directed an inquiry to take place before a medical board impannelled for the purpose, and the result of that inquiry may be guessed from a communication made by the War-Office to the commandant of the depôt. This states 'the unanimous opinion of the Board to have exculpated Dr Jackson from all improper treatment of diseases in the sick,' and the commander-in-chief's gratification, 'that an
opportunity has thus been given to that most zealous officer of proving his fitness for the important situation in which he is placed.' The result of this wretched intrigue, however, was that Jackson, disgusted with the whole affair, requested to be placed on half-pay, to which request the Duke of York, with marked reluctance, at last (March 1803) acceded.
In his retirement at Stockton, Jackson put forth two valuable works, one on the medical economy of armies, and another on that of the British army in particular, and was much gratified by an offer to accompany, as military secretary, General Simcoe, just appointed commander-in-chief in India. The general's sudden death, however, put an end to this plan; and Jackson continued at Stockton, addressing frequent representations to government on the defective medical arrangements in the military servicerepresentations the very receipt of which were not acknowledged by Mr Pitt, to whom they were forwarded. The Peninsular war commencing, Dr Jackson was again named Inspector of Hospitals, but was not, thanks to the persevering enmity of the Medical Board, sent on foreign service, although he volunteered to sink his rank, and go in any capacity. The Board even succeeded, by calumnious statements that he had purchased his diplomastatements he readily confutedin preventing his appointment to the Spanish liberating army; although the British government had formally requested him to accept such an appointment, and agreed to give credentials testifying to his capacity and trustworthiness. This last disappointment led him, in an unguarded momentpeppery to the lastto inflict a slight personal chastisement on the surgeon-general, for which he was imprisoned six months in the King's Bench.