362 S. HATAI 



physical data on the growth changes of the body and organs, 

 and also a complete record of the percentage of water in the 

 brain and of the composition of the entire body (Donaldson, '15) 

 all of which data can be advantageously utilized for the pur- 

 pose of cross reference. The rats employed in this study were 

 all in good condition, any appearing at all unhealthy having 

 been discarded. I have also used the sheep's brain for the study 

 of the white matter and the gray matter. These brains were 

 secured at a local slaughter house, immediately after the animals 

 had been killed. 



TECHNIQUE 



I have used 2.5 per cent trichloracetic acid for extracting 

 water soluble organic substances from nervous tissue. This 

 reagent was first used by Greenwald ('15) to precipitate proteins 

 as well as small quantities of fat which are present in the blood. 

 I have also found that this reagent not only precipitates proteins 

 but that it also precipitates completely the lipoids. It is re- 

 markable that the reagent gives a clear watery filtrate which is 

 entirely free from the lipoids even in the case of the nervous 

 tissue which contains more than 50 per cent of lipoids in its 

 solids. I have found it convenient to take about seven grams of 

 moist material for an analysis. The material is well ground in 

 a mortar and then well mixed with a small quantity of water 

 (5 cc). Then with an aid of 45 cc. of water the entire material 

 is transferred to a bottle. To this 100 cc. of 2.5 per cent tri- 

 chloracetic acid is added, and the mixture shaken well and 

 frequently for the first hour. The material remains in the solu- 

 tion for twenty-four hours (two or three hours are sufficient for a 

 complete extraction, but for convenience in carrying out my 

 working schedule I have left it for twenty-four hours). The 

 filtration is very easily made and one obtains a perfectly clear 

 solution. The following amounts of filtrate were taken for the 

 various determinations; 5 cc. for non-protein nitrogen, 20 cc. 

 for amino acids, 30 cc. for urea and ammonia and 40 cc. for 

 ammonia alone. Altogether 95 cc. are used and the remainder 

 kept for emergency purposes. 



