FIXING AND HARDENING AGENTS. 3-3 



mixture with oxalic acid lias been propounded by GRAF (Cont. Path. 

 Inst. New York State Hosp., 1898, No. 15; see Gruudziige, 4th ed., 

 p. 34). 



39. Chromo- acetic Acid (FLEMMING, Zellsbz., Kern. u. ZelltJi., 

 p. 382). 



Chromic acid . . 0*2 to - 25 per cent. 



Acetic acid . .O'l per cent, in water. 



Flemming found this the best reagent for the study of 

 the achromatic elements of karyokinesis. You can stain with 

 haematoxylin, or the basic anilin dyes. 



The following has been recommended for Annelids by 

 EHLERS : To 100 c.c. of chromic acid of 0'5 to 1 per cent, 

 add from 1 to 5 drops of glacial acetic acid. The acetic 

 acid is said to be sufficient to counteract any shrinkage due 

 to the chromic acid. 



Similar to this is the " chromo-acetic acid, No. 1," of Lo 

 BIANCO (Mitth. Zool. Stat. Neapel, ix, 1890,, p. 443), viz. 1 

 part 50 per cent, acetic acid and 20 parts 1 per cent, chromic 

 acid, which is found very useful for fixing marine animals. 



40. Chromo-formic Acid (RABL, Morph. Jahrb., x, 1884, 

 pp. 215, 216). Four or five drops of concentrated formic 

 acid are added to 200 c.c. of 0'33 per cent, chromic acid 

 solution. The mixture must be freshly prepared at the 

 instant of using. Fix for twelve to twenty-four hours, wash 

 out with water. Used by Rabl for the study of karyo- 

 kinesis. 



41. Chromo-osmic Acid (MAX FLESCH, Arch. mik. Anat., xvi, 1879, 

 p. 300). Osmic acid. 010 ; chromic acid, 0'25 ; water, lOO'O. Lo BIANCO 

 (Mitth. Zool. Stat. Neapel., ix, 1890, p. 443) employs for marine animals 

 a mixture of 1 part 1 per cent, osmic acid and 50 parts 1 per cent, 

 chromic acid. 



42. Chromo-aceto-osmic Acid (FLEMMING, Zellsubstanz, Kern 

 und Zelltheilung , 1882, p. 381). FIRST or WEAK formula : 

 Chromic acid. . . 0*25 per cent.l 



Osmic acid . . . O'l lin water. 



Glacial acetic acid . .O'l 



MEVES (Encycl. mikr. Teclm., 1, p. 475) sometimes adds 

 1 per cent, of sodium chloride. 



