EFFECTS OF FORMALDEHYDE ON BRAIN OF RAT 



295 



less than 5 per cent between the final weights. The very great 

 difference between the effects of the solution on the brains of 

 new-born animals and those on the brains of other ages is brought 

 out very clearly in the graphs in chart 4 which show the per- 

 centage weight changes for each set of brains during the four 

 weeks the experiments were continued. • 



New born 



Chart 4 Showing the weight changes in brains of rats of various ages, each 

 kept for 4 weeks in 40 cc. of a non-neutralized solution of 4 per cent formaldehyde. 



This series of experiments shows that the neutralization or non- 

 neutralization of a 4 per cent solution of formaldehyde has a 

 marked effect on the amount of swelling of the brain tissue. The 

 difference is shown in the graphs A and B of chart 5 which are 

 plotted from the final percentage weight increase in the various 

 sets of brains. As the weight of the brains of the new-born rats 

 kept in the neutralized solution is some 62 per cent greater than 

 that of the brains of the same age treated with the acid solu- 

 tion, the two graphs are very far apart at their beginning. At 

 the ten-day period the difference between the graphs is reduced 

 nearly one-half. They then approach gradually, and at the end 

 are comparatively close together as the final weighings of the 

 two sets of adult brains differed by only 10 per cent. 



