# Dictionary of National Biography, 1885-1900/Baron, John

​BARON, JOHN, M.D. (1786–1851), physician, of Gloucester, and the friend and biographer of Jenner, was born at St. Andrews, where his father was professor of rhetoric in the university. At the age of fifteen he was sent to Edinburgh to study medicine, and he graduated M.D. there four years later (1805), at the age of nineteen. He would appear to have taken a leading place among the students of his year, for he was elected one of the annual presidents of the Students' Royal Medical Society. In the year when he graduated his father died, and he prepared his college lectures for the press. He then attended a patient to Lisbon for two years, and on his return settled in practice at Gloucester. He was almost at once appointed one of the physicians to the General Infirmary, and soon acquired a considerable business. He practised as a physician in Gloucester and the surrounding country until 1832, when failing health (aggravated by the effects of an attack of Asiatic cholera) obliged him to retire. He resided at Cheltenham during the remainder of his life, disabled by ‘creeping palsy’ during his later years, but intellectually vigorous to the last. He was of a philanthropic and pious disposition, an early advocate, at the Gloucester asylum, of the more humane treatment of lunatics, which afterwards became general through the labours of Drs. Conolly and Tuke, a founder of the Medical Benevolent Fund, and an active supporter of the Medical Missionary Society of Edinburgh. He died in 1851.
Among his more distinguished friends were Dr. Matthew Baillie, who had a country house in the Cotswolds, near Cirencester, and Edward Jenner, who practised in the Vale of Berkeley, on the other side of the hills, sixteen miles from Gloucester. He came to know Jenner about 1809, by which time the latter had become eminent; and the intimacy grew to be such that he was naturally designated as Jenner's biographer by the executors. All the biographical materials, copious and well preserved, were put into his hands soon after Jenner's death in 1823; but the ‘Life of Edward Jenner, M.D., LL.D., F.R.S., with Illustrations of his Doctrine and Selections from his Correspondence,’ in two vols. 8vo, with two portraits, was not completed until 1838. The book is not only a serviceable history of the vaccination movement throughout the world, but is full of human interest of the more homely kind, and is put together with good sense and with considerable attention to style and proportion. Dr. Baron's literary merits are indeed greater than his scientific.
Tubercle was the subject upon which he published three books: (1) ‘Enquiry illustrating the Nature of Tuberculated Accretions of Serous Membranes,’ &c., plates, 8vo, London, 1819; (2) ‘Illustrations of the Enquiry respecting Tuberculous Diseases,’ plates, 8vo, London, 1822; and (3) ‘Delineations of the Changes of Structure which occur in Man and some of the Inferior Animals,’ plates, 4to, London, 1828. The theory of tubercle, which he seriously endeavoured to make good, may be said to have been in the air during those years. It came to him through conversation with Jenner, who, in turn, appears to have got some inkling of it from his master, John Hunter, and would have written on it himself had he not been preoccupied with vaccination. As it was, it fell to the lot of Dr. Baron to follow it out, and the idea underlying the inquiry proved, unfortunately, to be a misleading one. The idea was that tubercles were ‘hydatids’ become solid. Hydatids were then understood to include not only bladderworms, as at present, but almost any kind of vesicle filled with fluid, even cysts of the ovary. In the course of his practice, Dr. Baron found (in post-mortem examinations) a good many cases of tubercle of the serous membranes which appeared to him to suit the ‘hydatid’ theory. The tubercles on which his attention became fixed were peculiar. They were often suspended by a stalk, of ‘a pearly hue and cartilaginous hardness,’ with numerous small blood-vessels converging to the apex of the tubercle and spreading in a plexus over its surface. Sometimes they were exceedingly minute, in numbers defying all calculation, and woven into a fringe; others hung by themselves, of the size and shape of peas, or oblong and as large as beans, while some were of the size of hazel-nuts; the smaller were pearly and cartilaginous, and the larger contained a soft, creamy, yellowish matter. In one of the cases, ‘numerous fleshy and vascular appendiculæ or tubercles hung suspended like grapes into the cavity of the abdomen.’ These unique appearances recalled to Baron ​the fancy of Jenner (who was misled by the coexistence of tubercles and true hydatids in the lung of the ox), and led him to adopt the ‘hydatid’ theory of tubercle in general. Curiously enough, Dupuy, a French veterinarian, had been led two years earlier (1817), and independently of Baron, to adopt the same ‘hydatid’ theory to explain the hanging ‘pearls’ or ‘grapes’ which are the common form of tubercle in cattle. The coincidence of his own and Dupuy's observations had been found out by Baron before he published his second volume (1821), and the French veterinarian, as well as several old writers on human pathology, were marshalled in support of the theory. The theory is now completely discredited; but Baron's description of a variety of hanging tubercle in man, the same that has its proper habitat in the bovine species, is not likely to lose its interest. These services to pathological science, aided doubtless by his intimacy with Baillie and Jenner, procured him admission into the Royal Society in 1823.
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