364 METHODS. 



transfer it to fresh 80 per cent, alcohol, which must be changed until it no longer 

 extracts any iodine from the specimen. 



2. Tei^IvYEsnicky's Fluid. 



Formula: Bichromate of potassium 3 gm. 



Water, loo c.c. 



Immediately before using add 5 c.c. glacial acetic acid. 



This reagent is employed in the same manner as Zenker's fluid, except that the 

 treatment with iodine is omitted. 



3. PiCRO-SULPHURIC AciD. 



Fonnula : Picric acid, I gm. 



Sulphuric acid, 6 c.c. 



Water, 1000 c.c. 



Specimens are kept in the fluid from four to twenty-four hours, not longer, ac- 

 cording to their size; transfer to 30 per cent, alcohol for one hour,, to 50 per cent, 

 alcohol for one to two hours, to 60 per cent, alcohol for twelve hours, and finally 

 to 70 per cent, alcohol, which must be changed daily until it no longer shows even 

 a trace of yellow discoloration by picric acid. 



4. MulIvEr's Fluid. 



Formula: Bichromate of potassium, 20 gm. 



Sulphate of sodium, 10 gm. 



Water, 1000 c.c. 



Miiller's fluid is a valuable reagent, and for the study of the later stages of the 

 nervous system indispensable. The objections to its use are that it requires a 

 long time to act, that it renders the specimens brittle, and makes them some- 

 what difficult to stain. It must be used in large quantities and be frequently 

 changed, and allowed to act on the specimens from three to eight weeks according 

 to their size. The appearance of a film or scum indicates that the fluid needs to 

 be changed. 



5. Parker's Fluid. 



Formula:* 70 per cent, alcohol, 100 c.c. 



Formaldehyde, i c.c. 



Very convenient when a simple and expeditious preservative is necessary. The 

 specimens are placed in the fluid, which ought to be renewed in a few hours. 

 They may be kept permanently in the fluid, but it is desirable, before using them 



* Differs slightly from the original formula. 



