During this period he visited the different asylums for the insane in England and on the Continent, devoting his time almost exclusively to the great objects of his voyage. On his return he entered at once upon his duties as physician to the Bloomingdale Institution, and assumed the whole medical responsibility connected with its management. Eminently qualified by natural gifts, with a considerable share of personal experience before leaving home on his mission, full of zeal and of tact in the acquisition of such knowledge as is really practical, it will easily be understood that Dr. Macdonald entered upon his new duties, not only qualified to discharge them with the greatest success, but that he was destined to a still higher honor, that of becoming an authority and a counsellor to his profession. And such was the natural consequence of his position and of his acquirements, he was soon regarded, not only as the excellent physician of a large public institution, but as the first authority on mental diseases within the reach of his medical brethren in this city. At this time, indeed, his engagements did not allow him the liberty of a consultation practice, but in later life his reputation established at Bloomingdale, was not forgotten.

In the year 1837, Dr. Macdonald, having fulfilled his engagements with the Governors of the Bloomingdale Asylum resigned his situation in that Institution, much to the regret of all connected with it. The Governors, in accepting his resignation, expressed to him " the gratification they felt at the great success which for many years had attended his treatment of the insane patients, and assured him that they held in just estimation the amiable and gentlemanly deportment which had always characterised him during their long intercourse."