the highest and safest authority on its intricate and recondite subject-matter that as yet exists. We are not aware whether Dr. Thomson entered on the study of medicine with any view of going into the arduous and often unremunerative toils of private practice. If so, the idea must have been soon abandoned, as we have him, in 1832, becoming a Fellow of the Royal College of Surgeons, Edinburgh, and thereafter betaking himself, as an extra academical lecturer, to the teaching of the Institutes of Medicine. The labours of the class-room would seem, however, not to have in any way overtasked his energies, as we find that in the same year he was again before the public as an author. The publication which saw the light on this occasion was an "Essay on the Formation of New Blood Vessels in Health and Disease," a subject at once full of practical interest to both physician and surgeon, and a most natural supplement to the _magnum opus_ on the development of the vascular system. The same period, too, occasionally found Dr. Thomson not unwilling to appear before lay audiences with lucid, instructive expositions of the structure and functions of our wonderfully-made frame--a fact, we daresay, of which many middle-aged citizens of Edinburgh will, even still, retain a pleasing recollection. As regards his professional courses on physiology, these he continued to deliver up to 1836, when the removal of his colleague and intimate friend, Dr. Sharpey, from Edinburgh to the Chair of Anatomy and Physiology of the London University College, induced him to open classes for extra-mural students of anatomy, at that time a somewhat numerous body in the northern metropolis. As prelections and demonstrations on this fundamental important branch of medical study formed the daily vocation, at the period spoken of, of not less than three or four private lecturers--as they were termed--we can well imagine that the labours of Dr. Thomson, at this point of his career, would by no means be light. In 1839, however, a partial reward for his anxieties and toils came in the shape of an appointment to the Chair of Anatomy in Marischal College, Aberdeen, a situation which he had filled for three years, when he was recalled to the University of his native city to take the place of the late venerable and widely-venerated Professor Alison. The year which saw Dr. Thomson transferred to the granite city saw also a valuable contribution from his pen in the _Edinburgh Medical and Surgical Journal_, "On the Development of the Human Embryo," an elementary nucleus, among others, of a series of specially luminous articles by him on "Circulation," "Generation," and "Ovum," which afterwards appeared in "Todd's Cyclopediae of Anatomy and Physiology." After a six years' incumbency as Professor of Physiology in the University of Edinburgh, he was, in 1848, presented by the Crown to the Chair of Anatomy in Glasgow University, at that time vacant in consequence of the death of Dr. James