Brain Preservation 393 



There are two liquids which will cause the brain to retain 

 approximately its normal size ; one is glycerin which, 

 after it has thoroughly infiltrated the hardened tissues, causes 

 them to absorb moisture from the atmosphere and the natural 

 fluid is thus artificiall3^ replaced by means of this hy- 

 groscopic agent. There must, however, be some limit to 

 the preservative action, and the time may eventually 

 come when enough water will have been absorbed to cause 

 considerable deterioration. The other liquid is potassium bi- 

 chromate which, as noted in the table, caused an actual 

 "bloating" of the tissue, increasing both the weight and 

 girth of the specimen, and imparting an undesirable as well 

 as an unnatural color. The pia is a more or less inelastic and 

 pervious membrane, and while on the one hand it may retard 

 the penetration of the fluid, it serves a little later, in the case 

 of the bichromate to restrain the "bloating" and keep the 

 tissue within bounds. The pressure either from without or 

 within, would tend to disturb the normal relations of the his- 

 tological elements. 



Brains from animals of the same species react difi"erently 

 although subjected to exactlj' the same course of treatment. 

 The density of the tissue, the age and condition of the sub- 

 ject, the temperature and many other factors equally impor- 

 tant, are causes which contribute to these varying results. 



After considerable study and experimenting a fluid was de- 

 vised, which, though not ideal in its efi'ects, seems to answer 

 the requirements of economy, fixation of the structural ele- 

 ments, differentiation of tissue, a minimum amount of distor- 

 tion, firmness of texture, and rapidity of action. 



The formula is as follows : 



Water 400 c. c- 



95% Alcoholl 400 c. c. 



Glycerin 250 c. c. 



Zinc chlorid 20 grams. 



Sodium chlorid 20 grams. 



The specfic gravity of the mixture should be about 1.04, a 

 little greater than that of the brain itself (1.038). The 



