As a teacher Gregory was conspicuous for a sound practicality. He highly approved of a maxim which he often brought forward: “The best physician is he who can distinguish what he can do from what he cannot do.” Pathology in his days was a very rudimentary science, and hence he distrusted all theories in regard to the essential nature of disease as premature and visionary. He was at home in the study of diagnostic and prognostic symptoms, and paid considerable attention to the action of remedies. He had no tendency to meddlesome medicine, restraining and discountenancing treatment when there was no hope or prospect of success. He believed strongly in the antiphlogistic or lowering treatment of inflammatory diseases, and in the use of preventive measures in warding off the attacks of chronic diseases. Thus he presented the spectacle of an advocate of temperance, of bodily exertion without fatigue, and of mental occupation without anxiety, who by no means followed his own prescriptions. As a lecturer he displayed a most ready command of language, and an excellent memory especially for cases he had seen, the details of which he could accurately remember from the name alone of the patient. He gained great influence over the minds of his pupils, not merely by the humour and the abundance of his illustrations, but also by the outspoken exposition of his views and his commanding energy. His frankness showed itself too in the candour with which he communicated his opinions to the relatives or friends of his patients. He took a genuine interest in his patients, and convinced them of his sincerity, notwithstanding a certain roughness of manner. Where he felt no personal antagonism he was on very cordial terms with his professional friends, and succeeded in gaining their esteem and regard by his manner towards them in consultation. He was, as we have said before, the admitted autocrat of the profession in Edinburgh in his later years, and it is much to be regretted that his contributions to the science of medicine are so few.