EFFECTS OF FORMALDEHYDE ON BRAIN OF RAT 307 



Brainy of 70- and of 100-day-old rats suffer about the same 

 relative loss in substance when kept in a 4 per cent solution of 

 formaldehyde, amounting to about 5 per cent. The extraction 

 from adult brains is about 2 per cent, showing that formalde- 

 hyde has little solvent action on the brains at this stage. 



THE EFFECTS OF A 4 PER CENT SOLUTION OF FORMALDEHYDE ON 

 THE BRAINS OF RATS INFECTED WITH PNEUMONIA 



In the course of a study of the effects of pneumonia on the 

 brain of the rat (King '11) a small series of experiments was 

 made to ascertain whether the brains of animals suffering with 

 this disease would react as do the brains of healthy rats when 

 placed in a 4 per cent solution of formaldehyde. Five adult 

 rats which were in advanced stages of pneumonia were killed 

 with ether, and the brains removed at once and weighed. Each 

 brain was placed in 40 cc. of a stock solution of 4 per cent fonn- 

 aldehyde which had been neutralized with NaCOs. The brains 

 were kept in the solutions for one week, then weighed and the 

 percentage weight increase calculated. For control purposes 

 brains of five adult rats that were not suffering from any disease 

 as far as could be determined were treated in a similar manner. 

 The exact age of the rats used in these experiments was not 

 known in any case, but all the rats were from five to eight months 

 old. The age of the animal, therefore, was not a factor that 

 could have had any appreciable influence on the results. Table 

 1 1 shows the fresh brain weights of the control and of the infected 

 animals together with the percentage weight increase at the end 

 of one week. 



As shown in table 1 1 , the average fresh brain weight as wel) 

 as the percentage weight increase after treatment with 4 per cent 

 formaldehyde are practically the same for both groups of brains 

 used in this series of experiments. It would seem, therefore, as 

 if pneumonia, even in its advanced stages, does not produce any 

 changes in the brain tissues that affect the amount of swelling 

 of the brains when kept in a solution of formaldehyde. An 

 examination of the individual records, however, point to a dif- 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 23, NO. 4 



