2O MICROSCOPICAL -DIAGNOSIS. 



the mixture has a dark' purple color. An excess of this staining can 

 be removed with dilute acetic acid. 



Aniline blue-black. Dissolve five grains of aniline blue-black 

 in 100 c. c. of water. Dilute with water to any strength required. 



Sulphindigotate of soda, osmic acid, eosin, nitrate of silver, and 

 the various aniline colors, all have their general and special uses. 



The difficulty of preparing these staining reagents is such that 

 it is the wisest economy to purchase them, already prepared, from 

 some responsible dealer. 



MOUNTING. 



There is no substance more generally used for mounting pur- 

 poses than Canada balsam. It is used also in solution with benzole 



Fig. 6. Turn- Table. (R. & J. 



or alcohol. To prepare it in this way, a clear sample of the balsam 

 is taken and evaporated in a water bath until all odor of turpentine 

 has disappeared. This balsam will be hard and brittle when cold. 

 The hard balsam is warmed, and enough benzole or absolute alco- 

 hol added to dissolve the balsam, and make the solution, when cold, 

 of the consistence of thin syrup. To mount sections in this 

 medium, it is necessary to remove all water from them by transfer- 

 ring to alcohol, and from that to absolute alcohol. The alcohol is 

 then removed, and the oil of cloves added. When transparent the 

 oil is removed, and the sections are now ready for mounting. In a. 

 few weeks the mounts will become dry; this drying may be hast- 

 ened, of course, by keeping the specimens exposed to an elevated 

 temperature. 



