250 



ADVEXTURES IX RADIOISOTOPE RESEARCH 



PREPARATION OF CHLOROCADMIUM LECITHIN 



The ether extract of the brain was evaporated to dryness, the residue 

 was dissolved in alcohol, and a saturated solution of cadmium chloride 

 in methyl alcohol added. The chlorocadmium lecithin which precipitates 

 from the solution was further purified in the following manner : the 

 precipitate was suspended in chloroform and a solution of ammonia 

 in methyl alcohol added, whereupon the lecithin remained in solution 

 while the cadmium is precipitated. The next step was to evaporate 

 down the solution containing the lecithin, and to dissolve the latter 

 in alcohol; the whole purification process was then repeated. We ascer- 

 tained in our preliminary experiments that the above lenghty process 

 can be carried out with a yield of about 50%. In an experiment with 

 a rat's brain extract which showed an activity of 2.4 -lO'^ o^^ of the 

 total amount given to the animal, we recovered, after the preparation 

 of the chlorocadmium compound, lecithin containing 1.2 •lO"^ o^^ 

 of the total activity administered. 



INVESTIGATION OF THE BRAIN OF MICE 



As has been mentioned already it is of great importance to investigate 

 the brains of animals no longer growing. Through the kindness of Pro- 

 fessor Krogh and Dr. Hagedorn we obtained mice of unusually high 

 age and investigated their brain. The animal was killed 21 days after 

 injecting the labelled phosphorus. A result obtained was the following: 



Table 3 



INVESTIGATION OF THE BRAIN OF RABBITS 



The investigation of a brain of a rabbit killed 27 days (I.), resp. 4.5 

 hours (II.) after injection with radioactive phosphorus gave the follow- 

 ing result. 



Table 4 



