METABOLIC ACTIVITY OF NERVOUS SYSTEM 53: 
from the rat brain, I may state simply that the values for the 
alecohol-ether soluble fraction obtained in this series of fish are 
similar to those obtained by Von Bibra (’54) and by Schloss- 
berger (’56) in other forms of fish (table 3). 
CONTENT OF ‘NON-PROTEIN NITROGEN’ IN THE BRAIN 
Altogether 44 snappers of medium size were used for the 
purpose of determining the various extractive nitrogenous sub- 
stances in the brain. These brains were divided into three sam- 
ples, each giving nearly the same amount of moist brain weight. 
One additional sample was obtained from the brains of the school- 
master (Neomaenis apodus) which is a species most closely related 
to the gray snapper. 
The fresh brains of each sample were ground finely and then 
preserved in 150 cc. of 2.5 per cent solution of trichloracetic 
acid in water.- The ground brains were transferred to a bottle 
by means of 50 cc. water, thus making altogether 200 ce. of 
solution. The filtrates from this mixture were brought back 
to the Wistar Institute for analysis. The methods used for the 
determination of various nitrogen fractions were as follows: 
1. Total non-protein nitrogen. Micro method of Folin and 
Farmer as modified by Benedict and Bock. 
2. Amino-acid nitrogen. Van Slyke’s nitrous acid seine 
Also the same author’s micro apparatus. i 
3. Urea nitrogen. Urease method. 
4. Ammonia nitrogen. By the usual aerat on method. 
In all cases, except the case of the amino acid, the nitrogen 
content was determined by means of the DuBoseq colorimeter. 
The results obtained from these determinations are given in 
table 6. 
Since it is my intention to discuss this einen later in com- 
parison with the similar data recently obtained from the brain 
of the albino rat, I shall merely direct attention to the fact: that 
these three samples give results very close to each other... Fur- 
thermore the results obtained from the sample of the school- 
master also agree with those found in the case of the gray snapper. 
