OF MICROSCOPIC OBJECTS. 81 



CHAPTER IV. 



PRESERVATIVE LIQUIDS, ETC., PARTICULARLY WHERE CELLS ARE 



USED. 



THERE are many objects which would lose all their distinctive 

 peculiarities if allowed to become dry, especially those belonging 

 to the fresh-water Algae, many animal tissues, and most of the 

 very delicate animal and vegetable substances in which structure 

 is to be shown. These must be preserved by immersion in some 

 fluid ; but it is evident that the fluid must be suited to the kind of 

 matter which it is intended to preserve. As it often requires 

 much study and trouble to obtain microscopic objects of this class, 

 it is well that their preservation should be rendered as perfect as 

 possible ; and for this reason the CELLS, or receptacles of the 

 fluids, should be so closed that all possibility of escape should be 

 prevented. The accomplishment of this is not so easy a matter 

 as it might appear to the inexperienced. 



Before giving any directions as to the manipulation required in 

 mounting the objects, we must consider the different liquids and 

 cells which are requisite for their preservation. Of the former 

 there are a great number, of which the principal may be mentioned. 



DISTILLED WATER is strongly recommended by many for 

 Diatomaceae and other Protophytes. It has been, however, stated 

 that confervoid growths often disturb the clearness of the liquid, 

 and on this account various additions are made to it. A lump of 

 camphor is often left in the bottle, so that the water i#ay dissolve 

 as much as possible. One grain of bay-salt and one of alum are 

 added to each ounce of water ; or a drop or two of creasote shaken 

 up with the ounce of water, which should be afterwards filtered. 

 These additions are often -made ; perhaps each of them good for 

 certain objects. 



GLYCERINE. Some affirm this to be one of the best preserva- 

 tive liquids, especially for vegetable objects ; but others think that 



5 



