FIXING AND HAKDENING AGENTS. 65 



varies greatly- with different tissues. Mucin is not pre- 

 cipitated and remains transparent. Pat is not dissolved. 

 Micro-organisms retain tlieir specific staining reactions. 

 Formaldehyde is said to harden celloidin as well as gelatin, 

 and to be useful for celloidin-imbedding (Blum, Anat. Anz., 

 xi, 1896, p. 724). 



Several of the following mixtures are irrational, becoming 

 reduced more or less quickly, but may give good results all 

 the same. 



109. Alcoholic Formol (Lavdowsky, Anat. Hefte, iv, 1894, 

 p. 361.) — Water 40 parts, 95 per cent, alcohol 20, formol 6, 

 acetic acid 1 ; or water 30, alcohol 15, formol 5, acetic 

 acid 1. 



GuLLAND {Zeit. wiss. Mikr., xvii, 1900, p. 222) takes (for 

 blood) 1 part formol and 9 parts of alcohol. 



Bles {Trans. Buy. Soc. Edinhurgh, xli, 1905, p. 792) takes 

 1 of formol, 90 of alcohol of 70 per cent., and 3 of acetic 

 acid. 



Tellyesniczky (Encycl. mikr. Techn., i, p. 472) takes 5 of 

 formol, 100 of alcohol of 70 per cent., and 5 of acetic acid. 



110. Picro-Formol. — P. Bourn [Phcnomlnes cytologiques 

 anormavx dans L' Histogenesis, etc., Nancy, 1897, p. 19) 

 recommends — 



Picric acid, saturated aqueous sol. . 75 parts. 

 Formol . . . • • • 25 „ 



Acetic acid . . • ■ • 5 ,, 



Wash out with alcohol, first of 50 per cent., then 70 per 

 cent, till the picric acid is mostly removed. I consider this 

 to be for most purposes the most valuable fixative yet made 

 known. I have satisfied myself that the proportions are 

 exactly what they should be and cannot be changed without 

 hurt. It is rather a strong fixative, and should not be 

 allowed to act for more than 18 hours. If a weaker 

 mixture be desired, dilute the whole with water. The 

 penetration is great, the fixation equable, delicate detail 

 well preserved, staining qualities admirable, especially with 

 iron-hematoxylin and Saiirefuchsin. See also Gaeniee, 

 Bibl. Anat., v, 1898, p. 279. 



The formulae of Geap {State Eo>p. Bull. New Ycrlc, 1897 ; Jcurn. Eoy. 



5 



