Mercury, however, when prepared for medicinal use, is a remedy of the most extensive application. It is a powerful and general stimulant, but its effects are certainly different from those of other articles which are ranked in the same class. It enters into the circulation, quickens the vascular action, and excites powerfully the whole of the capillary system; increasing all the secretions and excretions, and has even been detected in the urine.5 It has been supposed that it is peculiarly determined to the salivary glands; but if, as there is every reason to suppose, these glands are endowed with more irritability1 than the rest of the habit, it is easy to conceive that the same degree of stimulus, which is operating on the whole system, will produce a greater effect on them in a direct ratio according to their greater susceptibility. But although the general action of the preparations of mercury is stimulant, yet they produce different effects, operating sometimes as stimulants, sometimes as cathartics, or emmena-gogues, and locally as errhines : and hence the great variety of diseases in which mercurials have been found useful; as febrile affections, spasms, cachectic diseases, glandular obstructions, cutaneous eruptions, membranous inflammation, etc. (See Preparations and Compositions.)

1 This method was invented by Professor Brunchi, of Pisa. Vide Phil. Mag. iv. p. 348.

2 Cavendish. 3 Crichton, Phil. Mag. xiv. 49.

4 Thomson's Chymistry, i. 175. If, however, the galvanic fluid be passed through it, the beautiful luminous stars in which it is dispersed seem to prove its combustibility.

5 Mem. della Reale Acad, di Torino, torn. xxix. p. 228.

But the most important effect of the preparations of mercury is their specific operation in syphilis. They were used, and their effects, when accumulated in the habit, were known so early as the 13th century; and the writings of Theodorick2 contain cautions against catching cold during the course; but the first notice of mercury as a remedy in lues venerea is contained in a tract by Jo. Almenar, a Spaniard, published in 1516, who recommends it after the manner of the Arabians, but condemns pushing the remedy so as to promote salivation. In a tract on Syphilis by Laurentius Phrisius, published in 15323, four formulae of ointments in which mercury is an ingredient are given under the title of Unguenta Empiricorum; but it does not appear that it had been used as an external application, by regular practitioners, from the year 1527, at which time it was introduced by Berengarius, a surgeon at Carpo. Physicians, however, did not venture to give mercury internally till Paracelsus broke the fetters of ancient authority, and proved that it might be exhibited not only with safety but with advantage.

Since his time, a period of nearly 300 years, experience has fully sanctioned its use : but although, as Mr. Pearson justly observes, "not one medicine besides, derived from the animal, vegetable, or mineral kingdom, has maintained its credit, with men actually employed in extensive practice, during a tenth part of that period4;" yet it is remarkable, that in the present day its utility in syphilis has been questioned.1 Many various theories of the operation of mercury have been advanced: the most satisfactory of which is that of Mr. Hunter, who supposed that the stimulant operation of the mercury induces and maintains an action which is incompatible with the morbid action produced by the venereal virus, until the poison is either destroyed, or evacuated from the body by the excre-tories. But, whatever may be the principles on which it operates, its efficacy in syphilis is certain, when it is judiciously and cautiously administered. The mode of giving it, and the morbid effects which it produces under certain circumstances, shall be mentioned when its preparations are described; it is only necessary to observe further in this place, that although men of the first medical talents have, occasionally, declaimed against its use2, and although much mischief may have of late years arisen from its indiscriminate employment by the speculative and the ignorant, yet, in the hands of judicious and cautious practitioners, it will continue to rank as one of the most useful of the articles of the materia medica.

1 That the salivary glands, and their excretories, are very excitable, is evident from the flow of the saliva being much increased by affections of the mind, as the thinking of any kind of food which is particularly grateful to the taste.

2 He was a friar, afterwards bishop of Cervia, and died between the years 1270 and 1280. See Friend's History of Physic, ii. 360.

3 Epitome opusculi de curandis pustulis, ulceribus, et doloribus morbi Gallici, mali Fruntzoss appellati, autore Lavrentio Phrisio, artium et medicinae, doctore.

4 Observations, etc. p. 97.

Officinal preparations.3

1. By distillation to purify the metal.

1. Hydrargyrum purificatum, D. Hydrargyrus purificatus, E. II. By trituration; (oxidized.) a. With animal fat.

2. Unguentum Hydrargyri fortius, L. Ung. Hydrargyria D. 3.----------------Hydrargyri, E.

4. -------------------------------mitius, L. D.

5. Linimentum Hydrargyri compositum, L.

6. Emplastrum Ammoniaci cum Hydrargyro, L. D. ----------------Hydrargyri, L. E.

b. With saccharine substances.

7. Pilulae Hydrargyri, L. E. D. e. With carbonate of lime.

S. Hydrargyrum cum Creta, L. D. d. With carbonate of magnesia.

9. Hydrargyrum cum Magnesia, D. III. By the action of heat and air; (oxidized.)

10. Hydrargyri Binoxydum, L. Hydrargyri Oxydum ru-brum, D.

1 Medico-Chirurg. Trans, vol. ix.

Saunders- Observations on the Hepatitis of India, etc. 3 In forming this table, we have been much assisted by the excellent table drawn up by Dr. Duncan, jun. in the. Edinburgh New Dispensatory; and we trust our alterations will render it more-practically useful.

IV. By the action of acids.

a. With sulphuric acid; (oxidized.)

11. Subsulphas Hydrargyri flavus, E. Oxydum Hydrargyri sulphuricum, D.

12. Hydrargyri Persulphas, D.

b. With nitric acid; (oxidized.)

13. Unguentum Hydrargyri nitratis, L. E. D.

14. Unguentum Nitratis Hydrargyri fortius, E. ---------------------------mitius, E. .

15. Hydrargyri Nitrico oxydum, L. Oxydum Hydrargyri rubrum per Acidum nitricum, E. Hydrargyri Oxydum nitricum, E.

16. Unguentum Hydrargyri nitrico-oxydi, L.D. Unguentum Oxydi Hydrargyri rubri, E. Unguentum Hydrargyri Oxidi-nitrici, D.

c. With chlorine.

† sublimed.

17. Hydrargyri chloridum, L. Submurias Hydrargyri mitis,

E. Calomelas sublimatum, D.

18. Pilulae Hydrargyri chloridi, L.

19. Hydrargyri bichloridum, L. Murias Hydrargyri corrosivus, E. Murias Hydrargyri corrosivum, D.

20. Liquor Hydrargyri Bichloridi, L. †† precipitated.

21. Submurias (chloridum) Hydrargyri pracipitatus, E.Calo- * melas prcecipitatum, D. d. With acetous acid; (suboxidized.)

22. Acetas Hydrargyri, E.D. e. With cyanogen.

23. Hydrargyri Bicyanidum, L.

V. By precipitation with earths and alkalies from acid solutions. a. By lime-water from the solution of the bichloride.

24. Hydrargyri Oxidum, L.

b. With liquor potassae from calomel.

25. Hydrargyri Oxydum nigrum, D.

c. By ammonia from the nitric solution; (suboxidized.)

26. Oxydum Hydrargyri cinereum, E.

d. By ammonia from the solution of the bichloride; (oxidized.) -

27. Submurias Hydrargyri ammoniatum, D. Hydrargyri

Ammonio-chloridum, L.

28. Unguentum Submuriatis Hydrargyri ammoniati, D. Ung.

Ammonio-chloridi, L.

VI. Combined with sulphur. a. By trituration.

29. Sulphuretum Hydrargyri nigrum, E. D. b. Sublimated.

30. Hydrargyrum Sulphuretum cum Sulphure, L. D. Hydrargyri Bisulphuretum, L.

VII. Combined with Iodine. a. By trituration.

31. Hydrargyri Iodidum, L. Hydrargyri Biniodidum, L.