FIXATION 645 



crystal of iodin should be added to the stronger alcohols until 

 decolorization no longer occurs. If the mercury is not thus re- 

 moved it will be difficult to obtain well stained specimens. 

 Flemming's Solution: 



1 per cent, aqueous solution of osmium tetroxid 40 cc. 



Glacial acetic acid. 5 cc. 



10 per cent, aqueous solution of chromic acid. . 7.5 cc. 



Distilled water 47.5 cc. 



Pieces of tissue should not be more than 2 to 3 mm. in thick- 

 ness and should be left in the solution and kept in the dark for 

 one to twenty-four hours, according to the results desired. For 

 mere fixation a short immersion is sufficient ; for blackening fat 

 and the myelin of medullated nerve fibres the longer period is nec- 

 essary. After fixation the tissues are to be washed in running 

 water for three to twenty-four hours, and hardened in graded 

 alcohol. 



This fluid gives excellent results for the fixation of the finer 

 cytological elements of glandular epithelium, and serves to demon- 

 strate the presence of fat and myelin, which are blackened by the 

 osmium tetroxid. It does not penetrate the tissues very readily, 

 and the surface of the piece is usually destroyed by overfixation. 

 Kleinenberg's Fluid : 



Saturated aqueous solution of picric acid 99 cc. 



Sulfuric acid. 1 cc. 



Shake well, filter, and dilute the filtrate with 200 cc. of distilled 

 water. 



Small pieces of tissue should be left in the fluid for about three 

 hours and then transferred to 67 per cent, alcohol, which is changed 

 two or three times during the first day. Hardening is continued in 

 82 and 85 per cent, alcohols, which are to be frequently changed. 

 The picric acid will be slowly dissolved by the alcohol, but will not 

 be entirely removed even after a considerable time ; a trace remain- 

 ing does no harm. 



This fluid gives excellent results with small pieces of embryonic 

 tissue, and possesses the additional advantage of removing the calca- 

 reous salts from partially calcified bone ; it is not, however, a strong 

 decalcifying reagent. 



Van Gehuchten's Fluid : 



Absolute alcohol 60 cc. 



Chloroform 30 cc. 



Glacial acetic acid . , , 10 cc. 



