396 Pierre A. Fish 



Stieda" immerses the brain in an aqueous solution of zinc 

 chlorid for twenty-four hours, as soon as it becomes firm 

 enough the pia is removed and the specimen is transferred to 

 ninety-six per cent, alcohol for two or three weeks, to de- 

 hydrate, it is then transferred for an equal length of time to 

 turpentine and finally immersed for two weeks or longer in 

 the ordinary commercial oil-finish. It is laid on blotting 

 paper to dry for about eight days, and acquires a dull brown 

 color on its surface. A shrinkage occurs which he considers 

 unimportant, about one fourth of the original volume being 

 lost. 



Teichman" has pursued a similar course, the difference being 

 that the brains were hardened in alcohol and finally impreg- 

 nated with " Damar-harz" or " Damar-lack." 



So far as Stieda knows Broca was the first to use nitric acid 

 for hardening the central nervous system. His formula is as 

 follows : 



Water 5 parts. 



Nitric acid i part. 



The brain is left in this mixture for two days ; the quantity 

 of the nitric acid is then doubled and after two days more the 

 specimen is taken out and allowed to dry and harden. There 

 is considerable shrinkage. A method of "galvanoplastie" de- 

 vised by M. Ore' is said to give good and durable specimens. 

 Duval has proposed a modification of Broca's method in that 

 the specimen is finally to be infiltrated with paraffin. 



Hyrtl'" (i860) saw no special advantage in using salts or 

 nitric acid combinations, and gave the preference to alcohol ; 

 the addition of sugar as recommended by Lobstein gives to 

 the specimen a welcome degree of flexibility. His experi- 

 ments on dry preparations were not wholly satisfactory ; the 

 brains of a hor.se and calf were utilized and after hardening in 

 sublimate were "cooked" in linseed oil and then allowed to 

 dry. They kept their shape for a couple of weeks but after 

 some months the horse brain shrunk to the size of a small 

 apple and that of the calf to the size of a nut. 



Giacomini' was the first to use glycerin for " dry " prepara- 

 tions ; his specimens have been highly commended for retain- 



