98 THE MICROSCOPIST. 



and Cetacea. Such differences make it quite possible to 

 distinguish the affinities of a fossil specimen from a small 

 fragment of tooth. 



In a similar way the microscopic characters of bone vary. 

 The bones of reptiles and fishes have the cancellated struc- 

 ture throughout the shaft, while the lacunee present very 

 great varieties, so that an animal tribe may be determined 

 by their measurement. In this way many contributions 

 have already been made to palaeontology. 



CHAPTER VIII. 



THE MICROSCOPE IN CHEMISTRY. 



THE value of microchemical analysis, and the simplicity 

 of its processes, commend this department of microscopy 

 to general favor. 



A large proportion of the actions and changes produced 

 by reagents may be observed as satisfactorily in drops as 

 in larger quantities. The decompositions effected by a 

 galvanic battery far smaller than that contained in a lady's 

 silver thimble, which deflected the mirror at the other end 

 of the Atlantic Telegraph Cable, may be readily observed 

 with a microscope. 



Apparatus and Modes of Investigation. A few flat and 

 hollow glass slides, thin glass covers, test-tubes, small 

 watch-glasses, a spirit-lamp or Bunsen's burner, constitute 

 nearly all the furniture which is essential. 



Dr. Wormley* directs that a drop of the solution to be 

 examined should be placed in a watch-glass, and a small 

 portion of reagent added with a pipette. The mixture 



* The Microchemistry of Poisons, fcy Dr. Wormley. 



