298 



HELEN DEAN KING 



Age of rat. 



Percentage weight increase. 



Time in days. 



Age of rat 

 , Ne^Af born. 



- 10 days. 



- 20 days. 

 .-40 days. 

 "■50 days. 

 "-70 days. 



100 days. 

 ' -200 days. 



Chart 6 Showing the weight changes in brains of rats of various ages, each 

 kept for four weeks in 20 cc. of a neutralized solution of 4 per cent formaldehyde. 



60 



Age of rat 

 10 days. - 

 ?0 days. 

 70 days.- 

 50 days. '40 

 40 days. 

 100 days 

 200 days. 

 New born.- ' 

 20 



30 



Percentage weight increase. 



Time in days. 



Age of rat. 

 .10 days. 

 -20 days. 



50 days. 

 - 70 days. 



40 days. 

 -100 days. 

 -200 days. 



New born. 



Chart 7 Showing the weight changes in brains of rats of various ages, each 

 kept for four weeks m 20 cc. of a non-neutralized solution of 4 per cent formalde- 

 hyde. 



