RUTHERFORD, DANIEL (1749–1819), physician and botanist, born at Edinburgh on 3 Nov. 1749, was son of Dr. John Rutherford (1695–1779) [q. v.], by his second wife, Anne, born Mackay. Educated at first at home, he was sent, when seven years old, to the school of a Mr. Mundell, afterwards to an academy in England, and thence to the university of Edinburgh, where, after graduating M.A., he entered on his medical studies. He studied under William Cullen [q. v.] and Joseph Black [q. v.], and obtained his diploma as M.D. 12 Sept. 1772, his inaugural dissertation being ‘De aere fixo dicto aut Mephitico.’ This tract owes its importance to the distinction, clearly established in it, between carbonic acid gas and nitrogen [see Priestley, Joseph]. It opens with an account of the work of Black and of Henry Cavendish [q. v.] on ‘fixed’ or ‘mephitic air’ (carbonic acid). Rutherford proceeds to point out (p. 17) that ‘by means of animal respiration’ pure air not only in part becomes mephitic, but also undergoes another singular change in its nature; for even after the mephitic air has been absorbed by a caustic lye from air which has been rendered noxious by respiration, the residual gas (atmospheric nitrogen) also extinguishes flame and life. The mephitic air he supposes to have been probably generated from the food, and to have been expelled as a harmful substance from the blood, by means of the lungs. He found experimentally that air passed over ignited charcoal and treated with caustic lye behaves in the same way as air made noxious by respiration; but that when a metal, phosphorus, or sulphur is calcined in air (probably in the case of the sulphur in the presence of water), the residual gas contains no ‘mephitic air,’ but only undergoes the ‘singular change’ above referred to. It follows then ‘that this change is the only one which can be ascribed to combustion.’ Rutherford gave no name to the residual gas (which has since been called nitrogen), but supposed that it was ‘atmospheric air as it were united with and saturated with phlogiston.’ John Mayow [q. v.] had already conjectured that the atmosphere was composed of two constituents, of which one remained unchanged in the process of combustion, and had supported this view by experiments. Moreover, practically all the facts and views recorded by Rutherford are to be found in Priestley's memoir published in the ‘Philosophical Transactions’ for 1772 (p. 230 and passim), and read six months before the publication of Rutherford's tract; but Priestley's exposition is less methodical and precise. Rutherford mentions that he had heard of Priestley's researches on the action of plants on mephitic air (p. 25), but makes no other reference to Priestley's work, which he had quite possibly not seen. Neither of the two chemists regarded the gas as an element at this time. Rutherford's comparison of putrefaction to slow combustion (p. 24) is interesting, although Priestley had also previously shown the similarity of the two processes.
Having published this valuable paper and completed his university course, Rutherford travelled in England, went to France in 1773, and thence to Italy. He returned in 1775 to Edinburgh, where he began to practise. He became a licentiate of the Royal College of Physicians of Edinburgh on 6 Feb. 1776, and a fellow on 6 May 1777. He was president of the college from December 1796 to Dec. 1798.
On 1 Dec. 1786 he succeeded Dr. John Hope as professor of botany in the university and keeper of the Royal Botanic Garden at Edinburgh, and was nominated a member of the faculty of medicine in the university, which brought him into connection with the royal infirmary as one of the clinical professors, and, on the death of Henry Cullen in 1791, he was elected one of the physicians in ordinary to that establishment. He was elected a fellow of the Philosophical (afterwards the Royal) Society of Edinburgh about 1776, and of the Linnean Society in 1796. He was also a member of the Æsculapian, Harveian, and Gymnastic Clubs.
When ten years old Rutherford suffered from gout, which increased in severity in later life, and was probably the cause of his sudden death, on 15 Nov. 1819, as he was preparing to go his usual round. He married, on 13 Dec. 1786, Harriet, youngest daughter of John Mitchelson of Middleton.
Besides the important dissertation referred to, Rutherford was author of ‘Characteres Generum Plantarum,’ &c., 8vo, Edinburgh, 1793, and of a paper containing ‘A Description of an Improved Thermometer’ in the ‘Transactions of the Royal Society of Edinburgh,’ vol. iii. A letter of his also appears in ‘Correspondence relative to the Publication of a Pamphlet, entitled “A Guide for Gentlemen studying Medicine at the University of Edinburgh,” by James Hamilton, jun., D. Rutherford, and James Gregory,’ 4to [Edinburgh, 1793].
A portrait in oils by Raeburn is in the possession of Mrs. Rutherford-Haldane; a replica hangs in the hall of the Royal College of Physicians in Edinburgh. This was en-