Allen that his younger son, the subject of the present sketch, stands indebted for the baptismal name he bears. Dr. John Gordon, who, half-a-century ago, was looked upon as one of the brightest and most promising ornaments of the Edinburgh Extra Academical Medical School, and whose early death was felt to be almost a public loss, was among his earlier favourite pupils; the late Sir James Simpson was one of the last. Dr. Thomson was from his youth quite a _helluo librorum_, and up to the close of a busy, laborious life, was a keen student and admirer of the ancient classical literature of his honourable profession. When an old man, it was no uncommon sight to see him whiling away a leisure hour with a well-thumbed Greek copy of the _Aphorisms of Hippocrates_ for his sofa companion. In a home so graced by all the amenities of lettered and scientific tastes, the subject of these remarks could not but enjoy, when a youth, many and great educational advantages. The tutorial shortcomings, if such there were, whether of High School or College, could not fail to be amply supplemented beside a domestic hearth predominated over by a father possessed of such force of character and well-garnered experience. As a student of medicine, Dr. Thomson held a distinguished place among his contemporaries, a circumstance which in due time earned for him the laurel-crown of Edinburgh studenthood, in the form of a presidency of the Royal Medical Society--a post of honour which had been occupied by his venerable father also, a quarter of a century before. His curriculum of professional study completed, and the necessary examinations passed, he obtained the degree of Doctor of Medicine from the University of Edinburgh in 1830. At this time it was yet the rule for the aspiring candidate, ere he could secure the longed-for degree, to compose and defend a Latin thesis drawn from some department or other of medical science, and this, like his fellows, had Dr. Thomson to do. "De Evolutione Cordis Animalibus Vertebratis," was the title of his dissertation, a subject wide as the poles apart from the customary jejune hackneyed topics figuring on such an occasion, and, at this period, one of all others, we would imagine, where learned professors, if modest men, would in all probability be the pupils, and the trembling candidate the instructor. It would appear from this that microscopic embryology has been with Dr. Thomson a favourite field of study and research from his youth upwards. The inaugural dissertation was, however, but a brief antepast of something more exhaustive to follow. In the same year in which he took his degree, we find him coming before the scientific world through the medium of the _Edinburgh New Philosophical Journal_, with a series of elaborate papers, entitled "The Development of the Vascular System in the Foetus in Vertebrated Animals," a contribution which is admitted on all hands, we believe, to be perhaps