Precipitated black oxide of Mercury, with Nitric acid and Ammonia. N 2 O 5 3Hg 2 O + 2NH 3 . (I have, in accordance with the usual custom, embraced both these preparations under the one head, their similarity being so great that no distinction is usually made in practice. Most of the symptoms are obtained from the solubilis , and in order to facilitate the student's knowledge, I have as far as possible designated those obtained from the vivus by an asterisk, those obtained from both preparations by a double asterisk. On account of the varying and doubtful composition of the solubilis , the vivus is usually considered the most reliable remedy, and has replaced the former to a great extent since Hahnemann's time, and even by Hahnemann himself in the latter years of his practice. I find the vivus of most use in affections of the mouth, throat, and respiratory organs, and in glandular swellings, while the solubilis seems to act more decidedly upon the alimentary and genitourinary tracts, and upon the skin. ( Dr. A. C. C .) acting upon these tissues by virtue of its presence in them. Its special action upon each we may more clearly comprehend by a careful study of the characteristic effects, as given below. The most essential feature of the action of Mercury is its remarkable resemblance to the effects of the syphilitic poison. Its chief characteristic is an aggravation of all the symptoms at night, and from the warmth of the bed. Dr. A. C. C.) General Analysis.- Mercurius acts profoundly upon the entire organism, affecting both the function and the substance of every organ and tissue of the body. Preeminently it operates upon the vegetative system, altering its functional power, both quantitatively and qualitatively, and decomposing and destroying its organic constituents. Secretion and absorption are both increased, and the secretions, losing their plasticity, become thinner and more fluid, and at the same time acrid and excoriating. On the organic system, Mercury acts more especially upon the mucous and serous membranes, the glandular system, the parenchymatous organs, the fibrous and osseous tissues, and the skin. The first condition produced is one of excitation-swelling and inflammation, soon followed by reaction, and subsequent weakness and exhaustion, which betokens commencing organic decomposition. The tissues above mentioned become the seat of destructive ulcerative processes, suppurations, and puriform collections, while there is, at the same time, a tendency to the deposition of new products, according to the character of the tissue involved. Thus we see that Mercury penetrates the entire organism, and permeates every tissue, acting upon these tissues by virtue of its presence in them. Its special action upon each we may more clearly comprehend by a careful study of the characteristic effects, as given below. The most essential feature of the action of Mercury is its remarkable resemblance to the effects of the syphilitic poison. Its chief characteristic is an aggravation of all the symptoms at night, and from the warmth of the bed. Characteristic symptoms.