FOR>L\TION OF PHOSPHATIDES IN THE BRAIN TISSUE OF ADULT ANIMALS 249 



by shaking a solution of laboUed sodium phospluilc wilh a large excess 

 of finely powdered unlabell(Ml sodium phosphate the former can ])e 

 removed from the solution. A distribution of the phosphate ions between 

 the liquid and solid phase takes place and the chance of a lal)elled phos- 

 phate ion being in solution is entirely negligible on account of the over- 

 whelming excess of the solid phase; this is especially so when the whole 

 procedure is repeated. Another method of purification of the ether 

 extract fiom the labelled inorganic phosphorus was as follows. Unlabelled 

 sodium phosphate was dissolved in the extract and precipitated as 

 ammonium magnesium phosphate. By repeating this procedure it was 

 possible to get rid of the slightest trace of labelled inorganic phosphorus 

 present in the ether extract. The activity of the ether extract had then 

 to be measured. The amount of material being small (2.3 mgm) it was 

 advisable to add a carrier. An inactive commercial lecithin preparation 

 was used for this purpose, some of it being dissolved in the ethereal 

 solution before evaporation. Before destroying the lecithin, calcium 

 oxide was added to bring about the formation of calcium phosphate. 

 The activity of the latter was measured by means of a Geiger— Miiller 

 Counter. 



INVESTIGATION OF THE BRAIN OF RATS 



All our investigations were carried out on fully-grown adult rats- 

 One animal was killed after a lapse of 5 days, a second one after a lapse 

 of 3 days, and the third one after one hour. The results obtained are 

 seen in Table 2. 



Table 2 



The above figures show clearly the formation of labelled phosphatide 

 in the brain of adult animals. Though it could hardly be doubted that 

 what we extracted and tested was actually phosphatide we obtained 

 further evidence of this preparing from the brain tissue of rats to which 

 labelled phosphorus had been administered, the highly characteristic 

 chlorocadmium compound of lecithin and tested its activity. 



