WITH THE MICROSCOPE. 197 



PART III. 



OF CHEMICAL ANALYSIS APPLIED TO MICROSCOPICAL INVESTIGATION 

 OF OBTAINING CRYSTALLINE SUBSTANCES OF SPECTRUM 

 MICROSCOPIC ANALYSIS. 



OF THE ADVANTAGES OF CHEMICAL REAGENTS IN MICROSCOPICAL 



INVESTIGATION. 



279. Of Chemical Analysis in Microscopical Investigation. I 



have already referred to the influence which the refractive power of 

 the medium in which any structure is immersed exerts upon it* 

 appearance in the microscope. We have now to discuss the 

 advantages derived from the chemical action of certain solutions 

 upon various specimens. This part of the subject is most important,, 

 and it is perhaps of all the various branches of microscopical 

 research, that from which the greatest advantages may be expected 

 to result. It is an investigation which will certainly reward all who 

 earnestly devote themselves to its study. It is certain that great 

 changes will take place in our views of the nature of many minute 

 structures when chemical analysis shall be more intimately associated 

 with microscopical enquiry. 



Although by the microscope we can say that such a texture is 

 granular, fibrous, opaque, perfectly clear, &c., we learn in such an 

 examination nothing more of its nature. Since these appearances 

 are manifested by several different materials, it is necessary to resort 

 to a chemical examination to discover the nature of the substance 

 to which the microscopical characters are due. If the composition 

 of any body having well-defined microscopical characters has been 

 once made out, by resorting simply to microscopical examination, 

 we are enabled to recognise it whenever we meet with it afterwards. 



Some bodies always produce well-recognised crystals when treated 

 with a certain chemical reagent, and we know that although there 

 may be in nature other crystals of a different composition, but of 

 precisely the same form, these latter could not be produced under 

 the same circumstances as the former; hence in such a. case we may 



