632 APPENDIX. 



hours; smaller ones in less time. After fixation, the specimens should be washed in several 

 changes of 30 to 50 per cent, alcohol, but not in water. A few drops of ammonia added to 

 the alcohol will facilitate the removal of the picric acid. Tissues thus treated will take a 

 brilliant differential stain (Weigert's haematoxylin, followed by eosin or acid fuchsin). 

 Bouin's fluid is also an excellent decalcifying agent (see technic, p. 218). 



3. Camay's fluid. 



Glacial acetic acid i part. 



Absolute alcohol 6 parts. 



Chloroform 3 parts. 



This is one of the quickest and most penetrating fixatives and prepares the tissues for almost 

 any stain desired. It has been used with success in studying developing muscle (see p. 315). 

 Wash with alcohol instead of water. 



4. Flemming's fluid. 



1 per cent, chromic acid 15 parts. 



2 per cent, osmic acid . 4 parts. 



Glacial acetic acid i part. 



The solution should be freshly made. It is perhaps the best fixative for nuclear structures, 

 but has the disadvantage of poor penetration. The objects to be fixed should not be more 

 than a quarter of an inch thick, and less if possible. Specimens should remain in the fluid 

 for 24 hours or longer. They are then washed in running water for several hours and trans- 

 ferred to graded alcohols up to 80 per cent. 



5. Formalin. Dilute i volume of commercial formalin with 9 volumes of water. (Com- 

 mercial formalin is a 40 per cent, solution of formaldehyde gas in water.) This diluted 

 fluid is usually called 4 per cent, formalin, although strictly speaking, it is 4 per cent, 

 formaldehyde. 



Formalin, in the solution mentioned above, can be used as a fixative with fairly good 

 results. It has the advantage of great penetrating power and consequently can be used with 

 large embryos. The specimens may remain in the fluid several days and should then be 

 carried through graded alcohols up to 80 per cent. 



6. Gils on's fluid. 



Absolute alcohol i part. 



Glacial acetic acid i part. 



Chloroform i part. 



Mercuric chloride to saturation. 



This is a very rapid fixative, and is much used for fixing objects that are highly impenetrable 

 Whole oviducts of Ascaris, for example, are fixed in from 15 to 30 minutes (see p. 33). 

 Specimens should afterward be washed in several changes of 70 per cent, alcohol containing 

 a few drops of tincture of iodine. 



7. Orth's fluid (Formalin-Mutter's fluid). 



Potassium bichromate 5 grms. 



Sodium sulphate 2 grms. 



Water 100 c.c. 



Formalin, 8 per cent. 100 c.c. 



This is a combination of equal parts of double strength Miiller's fluid and 8 per cent, for- 

 malin. The two should be mixed just before using. It is one of the best general fixatives 



