On the microscopic characters of the crystals of arsenious acid / by William A. Guy.

  • Guy, William A. (William Augustus), 1810-1885.
Date:
[1861]
Catalogue details

Licence: Public Domain Mark

Credit: On the microscopic characters of the crystals of arsenious acid / by William A. Guy. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    f/-h On the Microscopic Characters of the Crystals of Arseni- ous Acid. By William A. Guy, M.B. Cantab., Pro- fessor of Forensic Medicine, King^s College, London. (Read May 8th, 1861.) In submitting to your society tbis paper on the micro- seopic characters of the crystals of arsenious acid, I have two principal objects in view. I wish, in the first place, to illustrate, by a striking instance, the great value of the binocular microscope as a means of diagnosis; and, in the second place, to give a more exact account than any at present in existence of the crystalline forms assumed by a very important poison. That to render such an account is not a work of mere supererogation, a reference to the descriptions of the crystals given in works of authority would readily prove. Most authors describe the crystals as regular octahedra, without recognising any other crystalline forms. Some wi'iters, however, speak of the regular octahedron and its modifications, or of forms traceable to the octahedron; and acicular crystals, long prismatic needles, triangular and hexagonal plates, and even tetrahedra, are to be met with in the descriptions of authors.* I may add that, in illustrated works, the octahedral crystals are usually figured in the form in which they are most readily identified; the less usual positions of the octa- hedi’a and the rarer forms and modifications of the crystal being omitted. The imperfect and somewhat conflicting accounts thus given of the crystals of arsenious acid are, doubtless, to be explained, partly by the difficulty of examining them, whether by lens or microscope, when sublimed, as they were for- merly, in thick reduction-tubes of narrow bore; partly to the gi'eat variety of lights and shadows presented by the crystals, especially when viewed by transmitted light • and partly to the imperfect relief given to the crystals 'when examined by the monocular microscope. o Pereiras ‘Matena Medica,’ 4th edition, p. 685, in which nfV£-mentioned as one form of the crystal; Miller’s ‘Elements of Chemistry, part 11, p. 961, in which mention is made of long prismatic needles, isomorphous with those of oxide of antimony; and Taylor, on Poisons, 2d edition, p. 385, in which equilateral triangular plates are i 5