In pathology, or rather in nosology, by which latter term is meant the systematic arrangement and precise definition of diseases, his merits are very considerable. His practice was no doubt too limited, and of too short duration, to enable him to form, from his own experience, correct ideas of all the ailments to which man is liable; but it was sufficient to render him capable of methodizing the observations of others; and it requires little penetration to perceive, that one man may learn more in three years than another in fifty. The several classifications of diseases which have been given to the world, possess various degrees of accuracy. Dr Cullen of Edinburgh, whose Synopsis Nosologiae Methodicae has been almost universally acknowledged as one of the most successful attempts to reduce to order the complicated phenomena of morbid action, considers the Genera Morborum of Linnaeus as the most important work on the subject, next to that of Sauvages. It was first published in 1759 as an academical dissertation, and afterwards as a separate work. In the system now mentioned he arranges the genera of diseases under eleven classes, as follows:-- I. EXANTHEMATICI. Fevers attended with eruptions on the akin. II. CRITICI. Critical fevers. III. PHLOGISTICI. Fevers from local inflammation. IV. DOLOROSI. Painful diseases without fever. V. MENTALES. Diseases in which the functions of the mind are disturbed. VI. QUIETALES. Diseases in which the voluntary and involuntary motions and the senses are impaired. VII. MOTORII. Diseases attended with involuntary motion of parts whose action is ordinarily under the influence of the will. VIII. SUPPRESSORII. Diseases characterized by oppression of the organs, or impeded excretions. IX. EVACUATORII. Diseases attended with increased excretion. X. DEFORMES. Diseases causing deformity of the body, or change of colour in the skin. XI. VITIA. Cutaneous, external, or palpable diseases. Systems of nosology are no doubt useful or convenient, in the same manner as systems of zoology and botany; but so complicated are the phenomena of Nature, and so diversified her productions, that no arrangement, made according to any principles hitherto assumed, can possibly discriminate objects in conformity with all their connexions. If this remark required illustration, it might readily be afforded by the mere inspection of any one of the Linnaean classes or orders. Thus, in the class Vitia there are eight orders. 1. _Humoralia._ Diseases attended with vitiated or extravasated fluids; as emphysema, oedema, inflammation, abscess, and gangrene. 2. _Dialytica._ Solutions of continuity; as fracture, dislocation, contusion, wound, laceration, burn, excoriation, chapped skin. 3. _Exulcerationes._ Purulent solutions of continuity; as ulcer, cancer, caries, fistula, whitlow.