(b. Ballymoney, Antrim, Ireland, 26 April 1726; d. Dublin, Ireland, 28 December 1778)
Macbride’s father and grandfather were both Presbyterian ministers: his brother John rose to the rank of admiral in the British navy. Macbride chose a career in medicine and became apprenticed to a local surgeon after leaving the village school. He served as a surgeon in the navy during the War of the Austrian Succession (1740–1748) and then spent some time in Edinburgh and London, learning more about his profession from well-known teachers, before establishing a practice in Ballymoney in 1749. In 1751 he moved to Dublin.
His career seems to have met with only a limited success until after the publication of Experimental Essays(1764), which secured him a doctorate from Glasgow (prior to this he had no degree) and a European reputation. The work dealt with various aspects of a theory that Macbride had developed from Stephen Hales’s concept of air. “Hales’s observations of the expulsion of “air” from all kinds of materials, during heating and fermentation, led him to regard air as an essential constituent of all bodies. Its apparently dual nature-elastic in the free state yet capable of fixation in solids—prevented the component particles from coalescing into a “sluggish lump,” while at the same time it contributed to their union (Hales, Vegetable Staticks [London, 1727], pp. v-vi, 313–314).
Stressing the latter property (air as a “cementing principle”), Macbride attempted to apply the idea to medicine. He believed that it had been supported by Pringle’s experiments and confirmed by his own, which appeared to show that “air” freed from fermenting mixtures could counteract putrefaction. He believed that any mixture of animal and vegetable substances with water would ferment, hence the value of a mixed diet. The need for vegetable matter in the diet led to his advocacy of wort (an infusion of malt) in the treatment and prevention of scurvy. This method was favorably reported on by Captain Cook and others.
In one of his essays Macbride established the precipitation of chalk from limewater as a test for “fixed air”—(a phenomenon that confirmed his theory)—but he was unable to decide whether “fixed air” was a substance quite distinct from atmospheric air or simply a part of the latter modified by its fixation in solids.
His experiments with limewater led him to observe that it is more efficacious than plain water in extracting tannin from oak bark; and he petitioned the Irish parliament for recompense if he divulged his “secret” to Irish tanners, claiming that considerable time and money would be saved by his method. There is no record that his petition was successful; but the innovation was reported on favorably by the Dublin Society, and the discovery was eventually published.
Macbride was apparently a skilled surgeon and obstetrician, and his practice became lucrative. His medical treatise was accepted as authoritative and was translated into several European languages.
I. Original Works. Macbride’s writings include Experimental Essays (London, 1764, 1767); and A Methodical Introduction to the Theory and Practice of Physic (London, 1772), 2nd ed.,enl., A Methodical Introduction to the Theory mid Practice of the Art of Medicine, 2 vols. (Dublin, 1777). Some Account of a New Method of Tanning (Dublin, 1769) gives the advantages but not the secret of the method; the latter is given in “An Improved Method of Tanning Leather,” in Philosophical Transactions of the Royal Society, 68 (1778), 111–130.
II. Secondary Literature. The main biographical source is A. Smith, “David Macbride, M.D.,” in Dublin Quarterly Journal of Medical Science,3 (1847), 281–290. Macbride’s theory of air and some of its consequences are dealt with in E. L. Scott, “The ‘Macbridean Doctrine’ of Air…, in Arnbi. r,17 (1970), 43–57.
E. L. Scott