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HELEN DEAN KING 



Chart 5 Showing the final percentage weight increase in series of rats' brains 

 kept for four weeks in different quantities of neutralized and of non-neutralized 

 solutions of 4 per cent formaldehyde. A, 40 cc. of a neutralized solution used; 

 B, 40 cc. of a non-neutralized solution used; C, 20 cc. of a neutralized solution 

 used; Z), 20 cc. of a non-neutralized solution used. 



Series 4- As it is known from the experiments of Donaldson 

 ('94), Hrdlicka and others, that the amount of Hqiiid in which 

 brains are kept has a decided effect on the weight increase, the 

 present series of experiments was made to test this point with 

 brains of rats of various ages. The experiments were made 

 exactly like those in Series 3, except that the amount of solution 

 used was reduced from 40 to 20 cc. in every case. The data 

 obtained in the experiments in which the brains were kept for 

 four weeks in 20 cc. of a neutralized solution are given in table 6. 



A comparison of the data given in this table with that in 

 table 4 shows that the maximum, as well as the average, per- 

 centage weight increase is much lower when brains are treated 

 with 20 cc. of solution than when double this amount of solution 

 is used. This is the result one would expect if the amount of 

 swelling diminishes as the strength of the solution is increased; 



