770 MOLECULAR COALESCENCE. MICRO-CHEMISTRY. 



study of the relations between their structure and that of true 

 Bones and Teeth, the principle of ' molecular coalescence ' will be 

 found in some degree applicable to the explanation of the special 

 peculiai'ities of the latter. — The inquiry opened-up by Mr. Rainey 

 is one which may easily be pursued by any one who has leisure to 

 devote to it ; and will be almost certain to yield to the judicious 

 cultivator a rich harvest of valuable results. 



600. Micro -Chemisti^y of Poisons. — By a judicious combina- 

 tion 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* that Micro-Chemical analysis enables us by a very few 

 minutes' labour to recognize with unerring certainty the reaction 

 of the 100,000th part of a grain of either Hydrocyanic Acid, Mer- 

 cury, or Arsenic ; and that in many other instances we can easily 

 detect by its means the presence of very minute quantities of 

 substances, the true nature of which could only be otherwise de- 

 termined in comparatively large quantity, and by considerable 

 labour. This inquiry may be prosecuted, however, not only by 

 the application 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. Gruyf 

 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, Camphor, and Sulphur. The method of Sublima- 

 tion was afterwards extended by Dr. Helwig J to the Vegetable 

 Alkaloids, such as Morphine, Strychnine, Veratrine, &c. And 

 subsequently Dr. Guy, repeating and confirming Dr. Helwig's 

 observations, has shown that the same method may be further ex- 

 tended to such Animal products as the constituents of the Blood 

 and of Urine, and to volatile and decomposable Organic substances 

 generally. § It may be anticipated that by the careful prosecution 

 of Micro-Chemical inquiry, especially with the aid of the Spectro- 

 scope, the detection of Poisons and other substances in very minute 

 quantity will come to be accomplished with such facility and cer- 

 tainty as have until lately been scarcely conceivable. 



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



t "On the Microscopic Characters of the Crystals of Arsenious Acid," 

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



t " Das Mikroskop in der Toxikologie," 1865. 



§ " On Microscopic Sublimates ; and especially on the Sublimates of 

 the Alkaloids," in ' Trans, of Royal Microsc. Soc.,' Vol. xvi. (186S), p. 1 ; 

 also " Pharmaceutical Journal," June to September, 1867. 



