1913] Clayton S. Smith 59 



" Soluhle nitrogen" was determined by the Kjeldahl method, in 10 

 c.c. of an aqueous extract prepared in the foUowing manner : Twenty 

 gm. of water were added to each gm. of fish taken, but in prepar- 

 ing the extracts, an allowance was made for the water content of the 

 flesh, which was found to average 78.48 per cent. Approximately 50 

 gm. of flesh were used. After the extract-mixtures were prepared, 

 they were shaken thirty times and allowed to stand over night. Then 

 they were again shaken, allowed to settle and filtered. During filtra- 

 tion care was taken to prevent losses by evaporation. 



" Non-coagidahle nitrogen" was determined directly as follows: 

 100 c.c. of extract, prepared by the foregoing method, were heated 

 gently to boiling and then treated with 2 c.c. of a 2 per cent Solution 

 of acetic acid. When the liquid had again been carried to the boiling 

 point, the Solution was filtered directly into a Kjeldahl flask, Into the 

 beaker in which the precipitation had been made, were poured 50 c.c. 

 of distilled water. This was brought to the boiling temperature and 

 then used at once to wash the precipitate on the filter. The precipitate 

 was washed twice in this manner, after which the total ("non-coagu- 

 lable") nitrogen in the combined filtrate and washings was determined 

 as usual. 



From data obtained by the foregoing methods, the " insoluhle ni- 

 trogen" and " coagxtlahle nitrogen" were determined by difference. 



3. To prepare flesh for the determination of its content of lipins, 

 muscle was quickly removed from the fish, passed through a hashing 

 machine, and the hash dried at room temperature before an electric 

 fan, after which the residue was pulverized in a drug mill. Mixtures 

 of aliquot portions of each powder were used in the extractions, which 

 were made by the Soxhlet method upon 60 gm. charges, whenever 

 practicable. 



The acidity of the lipin mixture was determined by shaking the 

 sample with 50 c.c. of 95 per cent alcohol to which i c.c, of i per cent 

 Phenolphthalein Solution in 95 per cent alcohol had been added and 

 titrating with n/$ alkali Solution. A blank was always run simulta- 

 neously on the alcohol. 



4. The reducing power of aqueous extracts of fish muscle, after 

 removal of the protein, was determined by Benedict's^* method. The 

 extract was made by treating each gram of fish with 4 gm. of water. 

 Coagulable protein was removed by the method described above. 



We always ascertained the degree of acidity of the aqueous extracts, 

 as prepared for the various nitrogen determinations. Fifth normal 



1* Benedict: Joitrn. Am. Med. Assn., 1911, Ivii, p. 1193. 



