140 FIXATION 



Some authors delight in making trivial changes in well-known 

 formulae. Champy's fluid, ^^^ for instance, has this composition: — 



potassium dichromate, 3% aq. . . . 7 ml 



chromium trioxide, 1% aq. . . . 7 ml 



osmium tetroxide, 2% aq. . . • . . 4 ml 



This is a useful fixative for certain cytoplasmic inclusions. 

 Nassonov ^®* used the proportions 4:4:2 (he calls it Champy's 

 fluid, without comment). To this he adds a solution of pyrogallol, 

 measured in drops: the total amount of pyrogallol added is about 

 o-i mg to 10 ml of fluid. Pyrogallol could not exist for an instant 

 in the presence of vastly greater amounts of two very strong oxi- 

 dizers (chromium trioxide and acidified potassium dichromate) and 

 one moderately strong one (osmium tetroxide): it must at once be 

 changed to carbon dioxide and other oxidation-products. Yet 

 many cytologists continue to believe that there is some special 

 virtue in Nassonov's fluid. Actually there is none. This can be 

 proved by getting a friend to fix one set of objects in Champy's 

 fluid and another in Nassonov's, with secrecy as to which is which. 

 It will not be found possible to distinguish the final preparations. 



Fixatives are generally named after the persons w^ho invented 

 them. It has already been mentioned (p. 24) that it is often con- 

 venient to call them simply by the names of the inventors, without 

 necessarily saying So-and-so's fluid. This works well when the 

 inventor (Zenker, for instance) only introduces a single fixative. 

 When someone introduces two or more, descriptive words are 

 necessary. Thus one may refer to Flemming's weak ^'^^ and 

 strong ^"^ mixtures. It is desirable in such cases that the inventor 

 should himself suggest suitable names. Heidenhain ^^^ named one 

 of his fluids Susa, combining into a single word the first two letters 

 of each of the words Suhlimat and Sdiire. (Some authors have 

 supposed Susa to be a person.) It is thoughtless of an inventor to 

 call a fluid by the number that it happens to receive in his labora- 

 tory note-book ('B.15', for instance, or '2BD'), for this has no 

 mnemonic value for others. 



In some cases the reduction or omission of one constituent 

 radically changes the nature of a fixative, and a change of name is 

 then desirable. Flemming's strong fluid ^"^ contains i Maastheil 

 oder weniger of acetic acid to 19 of other constituents. Benda ^^ 

 reduced the amount to 3 drops of acetic to 19 ml of other constitu- 

 ents: Lewitsky ^^^ omitted the acetic acid altogether. Flemming's 



