The year 1785 was that in which Hunter first tied the femoral artery in a case of popliteal aneurism, and thus initiated one of the greatest modern improvements in surgery, relying upon the enlargement of the smaller communicating or collateral vessels to make up for the cessation of circulation through the principal vessel. This appears to have been suggested to him by an experiment on the mode of growth of deer’s antlers. Having been granted by the king the privilege of experimenting with the deer in Richmond Park, he tied one of the external carotid arteries supplying (_inter alia_) one of the half-grown antlers. The antler became cold, but after a week or two Hunter, to his astonishment, found that it had again become warm and was growing again. On a _post mortem_ examination he discovered that this continued growth was due to the enlargement of small branches of the carotid above and below the wound, to an extent sufficient to restore the blood-supply in the antler. And by a stroke of genius Hunter saw that a similar process might be expected to occur in cases of aneurism, and supersede the then generally fatal methods of operating by means of amputation, or by directly evacuating the sac of the aneurism. The fourth patient Hunter performed the new operation upon lived for fifty years; a specimen illustrating the case is preserved in the Hunterian Museum. In 1786, on the death of Middleton, Hunter received the appointment of deputy surgeon-general to the army; becoming in 1790, on the death of Mr. Adair, surgeon-general and inspector of hospitals. In 1786 he published his long-deferred work on the Venereal Disease, which, though printed and sold in his own house, met with a rapid sale, and proved a very valuable work. In the same year he collected a large number of his papers contributed to the Royal Society, together with others not previously published, into a quarto volume entitled, “Observations on certain Parts of the Animal Œconomy,” and thus placed his researches in imposing bulk before the general public. The Copley Medal of the Royal Society was awarded to Hunter in 1787 for his discoveries in natural history.