Brain Preservation 395 



inflexible ; the other involves the infiltration of the tissue by 

 some hygroscopic substance like glycerin which replaces the 

 natural fluid by abstracting the requisite amount of moisiure 

 from the air. Such specimens, of course, are not dehydrated 

 and therefore are not dry in the same sense as those of the 

 former class. 



A temporary dry preparation of the brain for demonstrative 

 purposes has been recommended by von Lenhossek". After 

 thorough hardening in alcohol, the specimen, when needed 

 for demonstration, is carefully dried in soft linen and then 

 coated with a thin layer of celloidin applied with a fine brush. 

 After five or ten minutes the celloidin dries, and as a thin, 

 transparent, tough membrane affords great protection and firm- 

 ness to the preparation. If exposed to the air for more than 

 two hours the specimen will begin to .shrink and should be re- 

 turned to the alcohol. 



Paraffin impregnation of brain tissue for dry preparations was 

 first employed by Fredericq'. Schwalbe'"* in the same year 

 (1876) adopted Fredericq' s method slightly modified. The brain 

 is hardened in zinc chlorid or alcohol, the membranes are re- 

 moved and the specimen cut into suitable pieces, impregna- 

 tion in toto does not seem to be advisable. After dehydrating 

 in strong alcohol, immerse in turpentine until completely sat- 

 urated, then infiltrate with soft paraffin at a temperature of 

 60° C. from five to eight days and let cool on a layer of cotton 

 taking care to avoid deformation. W. C. Krauss" and others 

 have employed a similar method and recommend it for friable 

 specimens. 



Dr. J. W. Blackburn's' method consists of allowing the 

 specimen to harden for about five weeks in Miiller's fluid, the 

 pia being removed after a few days immersion. After 

 thorough dehydration in alcohol it is placed in a saturated 

 solution of Japan wax (a concrete oil, the product of i?,^z« suc- 

 cedenea) in chloroform. When the alcohol has been displaced 

 the specimen is transferred to a bath of pure melted wax and 

 kept there at the melting point (42° to 55° C), until 

 thoroughly infiltrated. Upon removal the wax drains from 

 the surface leaving it perfectl}' smooth. A small proportion 

 of parafiin will prevent cracking. 



