326 THE MICROSCOPE AND ITS REVELATIONS. 



further prosecuted by Dr. "W. M. Ord, with express reference to the for- 

 mation of Urinary and other Calculi. 2 



714. Micro -Chemistry of Poisons. By a judicious combination of 

 Microscopical with Chemical research, the application of re-agents may 

 be made effectual for the detection of Poisonous or other substances, in 

 quantities far more minute than have been previously supposed to be 

 recognizable. Thus it is stated by Dr. Wormley, 2 that Micro- Chemical 

 analysis enables us by a very few minutes' labor to recognize with unerr- 

 ing certainty the reaction of the 100,000th part of a grain of either 

 Hydrocyanic Acid, Mercury, or Arsenic; and that in many other in- 

 stances we can easily detect by its means the presence of very minute 

 quantities of substances, the true nature of which could only be other- 

 wise determined in comparatively large quantity, and by considerable 

 labor. This inquiry may be prosecuted, however, not only by the appli- 

 cation of ordinary Chemical Tests under the Microscope, but also by the 

 use of other means of recognition which the use of the Microscope affords. 

 Thus it was originally shown by Dr. Guy 3 that by the careful sublimation 

 of Arsenic and Arsenious Acid, the sublimates being deposited upon 

 small disks of thin-glass, these are distinctly recognizable by the forms 

 they present under the Microscope (especially the Binocular) in extremely 

 minute quantities; and that the same method of procedure may be applied 

 to the volatile metals, Mercury, Cadmium, Selenium, Tellurium, and some 

 of their Salts, and to some other volatile bodies, as Sal-Ammoniac, Cam- 

 phor, and Sulphur. The method of sublimation was afterwards extended 

 by Dr. Helwig 4 tothe Vegetable Alkaloids, such as Morphine, Strychnine, 

 Veratrine, etc. And subsequently Dr. Guy, repeating and confirming Dr. 

 Helwig's observations, has shown that the same method may be further 

 extended to such Animal products as the constituents of the Blood and of 

 Urine, and to volatile and decomposable Organic substances generally. 5 

 By the careful prosecution of Micro-Chemical inquiry, especially with the 

 aid of the Spectroscope (where admissible), the detection of Poisons and 

 other substances in very minute quantity can be accomplished with such 

 facility and certainty as were formerly scarcely conceivable. 



1 See his Treatise " On the Influence of Colloids upon Crystalline Form and 

 Cohesion," London, 1879. 



2 " Micro-Chemistry of Poisons," New York, 1867. 



3 * On the Microscopic Characters of the Crystals of Arsenious Acid,' in 

 " Trans, of Microsc. Society," Vol. ix. (1861), p. 50. 



3 " Das Mikroskop in der Toxikologie," 1865. 



5 ' On Microscopic Sublimates; and especially on the Sublimates of the Alka 

 loids,' in "Trans of Royal Microsc. Soc.," Vol. xvi. (1868),p. 1; also "Pharma. 

 ceutical Journal," June to September, 1867. 



