— 175 — 



designateci by the letter C. Both mixtures were put together 

 in the incubator at 37° and left there for Q6 hours. During the 

 incubation the mixtures were shaken repeatedly. The period of 

 incubation over, mixture A was acidified with a few drops of 

 acetic acid and heated to boiHng point. Mixture C having been 

 already heated it was unnecessary to repeat this operation. When 

 cool both mixtures were poured into a graduated cyhnder and 

 filled with water until their volume , together with the precipi- 

 tate, had become exactly ten times greater than the quantity of 

 brain employed ; then they were well shaken and filtered through 

 a dry filter. In this way 10 e. e. of filtrate correspond exactly 

 to one gram of brain. 



In the filtrates so obtained the dry residue , ash , organic 

 matters , total nitrogen , purine-nitrogen and phosphorus were 

 determined. 



With regard to the chemical analysis both of the brain and 

 of the filtrates they were executed in the following way : 



1. The dry residue was determined at a temperature 

 of 110". 



2. The ashes were determined by carbonizing the dry 

 residue, carefully, in a platinum capsule; extracting the soluble 

 salts with water and igniting the residue till the carbon was com- 

 pletely burned; then the solution of the soluble salts was added to 

 it and the whole was evaporated to dryness, at first on the wa- 

 ter bath and then heated carefully to a red heat over a Bunsen 

 flame. 



3. The organic matters are calculated by the difference 

 between the dry residue and the ash. 



4. The nitrogen was estimated according to Kjeldahl 

 employing copper sulfate as catalysator. For titrating, decinormal 

 sodium hydrate and hydrochloric acid solutions were employed 

 and rosolie acid as indicator. 



5. Purin-bases nitrogen. The solution to be treated 

 was first alkalized with ammonia and filtered from the precipi- 

 tate formed. The filtrate was then treated with an ammoniacal 

 Silver nitrate solution and left in a dark place for 24 hours. The 

 precipitate of the Silver compound of the purin-bases was filtered 

 through a quantitative filter, washed, at first, with ammoniacal 



