378 fiHArTEi; xxxr. 



a.ngmerits in weight slightly in 10 per cent, forniol solution 

 (spinal cord somewhat move) ; whilst in 1 per cent, solution 

 it may increase as much as 24 per cent. 



Gkkota {Zeit. ivi'ss. Mik., xiii, 1896, p. 314) puts human 

 brains into a 5 or 10 per cent, solution of formol, and after 

 twenty-four hours removes the pia and changes the liquid ; 

 this is also further done every five to seven days, and in one 

 or two weeks the hardening is complete. In the case of 

 foetal brains of Gnnis, Feli^, and Homo, he first injects the 

 vascular system with a 10 to 15 per cent, solution of formol 

 in 85 per cent, alcohol, and then brings the heads into the 

 5 to 10 per cent, watery solution ; after one or two daj'.s he 

 removes the brains from the skull and puts them back for 

 fifteen to twenty days into the formol. 



Kadti {Poln. Arch. Biol. Med. Wif<s., i, 1901, p. 80) takes 

 5 ]ia,rts of formol, 100 of water, and 2 of bicarbonate of soda, 

 for four to ten days. 



Hrdlicka [Proc. IT. S. N((f. Mit..9., XXX, 1906, p. 304) takes 

 3 parts of formol, 25 to 45 of water, and 72 to 52 of alcohol 

 of 95 per cent. 



Streckee (Zeif. lom. Mil:., xxviii, 1911, p. 17) fixes small pieces for 

 twenty -four to forty-eight hours in 1 part of formol of 10 or 20 percent, 

 with 1 part of EIu-lich-Biondi triacid mixture, and imbeds in paraffin, 

 thus getting a stain at the same time as a fixation. Similarly with 

 toluidin blue, fixing it with ammonium molybdate. 



742. Chromic Salts. — That most used is the bichromate of 

 potash. 



The liquid of Erlicki has a more rapid action than the 

 other solutions of chromic salts. Sahi.i, however (loc. cif., 

 § 739), after liaving studied the action of the usual solution.s, 

 concludes that the best hardening agent for fresh tissues is 

 2vire hichroviafe of pota.ih, in 3 or 4 per cent, solution, the 

 hardening being done in a cold jilace. He rejects the liquid 

 of Erlicki on account of the precipitates it so frequently 

 gives rise to (see § 54) . 



Obeesteineh is of the same opinion, recommending pure 

 bichromate for general hardening purposes ; whilst for the 

 study of the most delicate structural relations he recommends 

 fixing in Fol's modification of Fleniming's liquid (§ 42) for 

 twenty-four hours, followed by washing with water and 

 hardening in SO per cent, alcohol. 



