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. 



Hj^rtl'" (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 lyobstein gives to 

 the specimen a welcome degree of flexibility. His experi- 

 ments on dry preparations were not wholly satisfactory ; the 

 brains of a horse and calf were utilized and after hardening in 

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

 dry. The}^ 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- 



