COLLECTING, FIXING, &c. 7 



&c., when it is intended only to show the position of the various parts 

 of which such specimens are composed. By the action of the spirits 

 on the specimens, resinous substances will be dissolved out, and the 

 spirits become discoloured. The latter should now be poured off and 

 the specimens covered with fresh spirits, in which they may remain 

 indefinitely. For the fixation of cells, cell-contents, nuclear division, 

 &c., of both plants and animals some specific fixative must be used, so 

 as to fix and preserve them in their natural condition. As a general 

 rule the reagents best suited for this purpose are: — 



1. Osmic acid. 



2. Chromic acid. 



3. Acetic acid. 



4. Picric acid. 



5. Corrosive sublimate. 



6. Formaldehyde. 



These are combined to suit the purposes for which they are 

 intended, the formulae found most useful are made up as follows : — 



I. Flemmings Fluid. 



25 cc. of I per cent, chromic acid, 



10 cc. of I per cent, glacial acetic acid, 



55 cc. of water, and immediately before use add 



10 cc. of I per cent osmic acid. 



For use this solution should be taken into the field and immediately 

 the specimens are collected they should be cut into as small pieces as 

 possible compatible with the purpose for which they are required and 

 placed directly into the solution, and allowed to remain there sufficiently 

 long for it to completely penetrate the tissue. This will vary from one 



