FIXATION 729 



xylol in the embedding process. II docs not penetrate the tissues very 

 readily, and the surfaces of the piece are usually destroyed by over- 

 fixation. 



Kleinenberg's Fluid: 



Saturated aqueous solution of picric aeid 99 c.c. 



Sulphuric acid 1 c.c. 



Shake well, filter and dilute the nitrate with 200 c.c. of distilled water. 



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

 hours and then transferred to 70 per cent, alcohol, which is changed 

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

 80 and 95 per cent, alcohols, which are to be frequently changed. The 

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

 tirely removed even after a considerable time; a trace does no harm. 



This fluid gives excellent results with small pieces of embryonic 

 tissue; and possesses the additional advantage of removing the calcareous 

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

 ing reagent. 



When a fixative is employed which contains picric acid, the tissue 

 must never be washed in water, but is transferred directly to 70 per 

 cent, alcohol. 



Bouin's Fluid: 



Picric acid, saturated aqueous solution 75 c.c. 



Formalin 20 c.c. 



Glacial acetic acid 5 c.c. 



Small pieces of tissue are fixed from three to twelve hours, trans- 

 ferred to 70 per cent, alcohol, and then passed through the higher 

 grades. This is an excellent fluid for the fixation of embryonic ma- 

 terial. For chromosome studies it is probably surpassed only by Flem- 

 ming's fluid. 



Van Gehuchten's Fluid (Carnoy's fluid, Xo. I) : 



Absolute alcohol 60 c.c. 



Chloroform 30 c.c. 



Glacial acetic acid 10 c.c. 



Very small pieces of tissue should be used. They should be left in 

 the fluid three to twelve hours, and the vessel tightly closed to prevent 

 evaporation of the volatile fluid. The tissues are then transferred to 

 46 



