The Microscope. 247 



CHALK AND BARYTA WATKKS. 



These are chiefly used in making preparations of tendons, 

 and connective and elastic tissues. The first requires about 24, 

 the latter only 6 hours. 



POTASSIUM HYDRATE. 



A trial with each case must decide the strength of the re- 

 agent to be used. 



N. B. — In using an alkaline fluid, it is well to follow it with 

 a very dilute acid, so that the actions of either may be certainly 

 stopped at any desired point. 



DECALCIFYING. 



CHROMO-NITRIC ACID. 



Chromic Acid \ c / 70 vols. 



Nitric Acid 3 vols. 



Water 200 vols. 



PICRO-NITRIC ACID. 



Water 95 vols. 



Nitric Acid ., 5 vols. 



Picric Acid in crystals, as much as will dissolve. 



In the study of developing bone or teeth, the soft parts of 

 adult bone, and animals whose integuments are impregnated 

 with lime (radiates, etc.), the fluids are indispensable in remov- 

 ing calcium so that sections can be made. Its action on the soft 

 parts is to harden them and to preserve their every characteristic 

 and relation, while the lime is dissolved and retained in solution. 

 A large quantity of the solution should be used and renewed as 

 often as it becomes exhausted, and to bring all portions of the 

 acid in contact with the object, it should be frequently well 

 stirred, with a glass or wooden rod ; no metal should ever be 

 placed in the bath. The specimens may be tested from time to 

 time with a fine needle, care being taken, however, not to pass 

 it through a part which it is desired to study. The above two 

 fluids may de used on the fresh specimens as they are good fixa- 

 tives, or the objects may be first killed and hardened and then 

 decalcified. In all cases it is very necessary to completely ex- 

 tract the acid. 



REMOVING SILICA. 



This is done by immersing the well hardened specimens 



