FORMIC ACID. 35 



In the Traite des Meth. Techn., 1887, 1 stated that the reason 

 why glacial acetic acid was not more used was that it did not 

 faithfully preserve delicate histological and cytological detail. 

 I now believe that if the instructions above given be followed, 

 in particular as regards the employment of the glacial acid, 

 and the washing out with somewhat strong alcohol, the 

 most delicate detail will generally be found admirably pre- 

 served. 



52, Acetic Alcohol (CAENOY, La Cellule, t. iii, 1, 1886, p. 6; 

 and Ibid., 1887, 2, p. 276 ; v. BENEDEN et NEYT, Bui. Ac.roy. d. 

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

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

 CAENOY has given two formulae 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. 

 ZACHAEIAS 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. 



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

 a, 51). It is probable that it might also take the place of acetic 



