FORMIC ACID. 37 



delicate detail will generally be found admirably preserved. 

 I see no reason why other energetic reagents should not be 

 combined with the glacial acetic acid if desired. Dr. LINDSAY 

 JOHNSON (in. litt.) has found that the best of all fixatives for 

 retina is a mixture of equal parts glacial acetic acid and 2 per 

 cent, osinic acid. 



54. Acetic Alcohol (CARNOY, La Cellule, t. iii, 1, 1886, p. 6 ; 

 and ibid., 1887, 2, p. 276 ; v. BENEDEN et NEYT, Bull. Ac. roy. d. 

 sci. de Bdg., t. xiv, 1887, p. 218; ZACHAEIAS, Anat. Anz., iii 

 Jahrg., 1, 1888, pp. 2427; v. GEHUCHTEN, ibid., 8, p. 237). 

 ' CAENOY has given two formulse for this important reagent. 

 The first is 



Glacial acetic acid . . .1 part. 

 Absolute alcohol . . .3 parts. 

 The second is 



Glacial acetic acid . . .1 part. 

 Absolute alcohol . . .6 parts. 

 Chloroform . . . . 3 

 The addition of chloroform is said to render the action of 

 the mixture more rapid. 



V. BENEDEN and NEYT take equal volumes of glacial acid 

 and absolute alcohol. 

 ZACHARIAS takes 



Glacial acetic acid . . .1 part. 

 Absolute alcohol . .4 parts. 



Osmic acid . . . .A few drops. 

 Acetic alcohol is one of the most penetrating and quickly 

 acting fixatives known. It preserves nuclei admirably, and 

 admits of admirable staining in any way that may be pre- 

 ferred. It was imagined by all of the authors quoted for the 

 study of karyokinesis in the ova of Ascaris, proverbially one 

 of the most difficult objects to fix, but it is applicable to 

 tissues in general. You may wash them out with alcohol and 

 treat them afterwards in any way that may be preferred. It 

 will be well, however, to avoid treatment with water as much 

 as possible. 



55. Formic Acid may be used dilute in the same way as acetic acid 

 (supra, 53). It is probable that it might also take the place of acetic 

 acid in the concentrated form, but I am not aware of any experiments in 

 this direction. 



