Johnson. — Food Values of Neiv Zealand Fish. 21 



mixed. Then, after a portion had been set aside for the estimation of 

 the water and protein percentage, the rest was spread in thin layers on 

 glass plates and dried, either over a low-temperature water-bath or in an 

 oven maintained at 52° C. Some oxidation of the fat was unavoidable 

 in this process. The dried material was minced again, passed through a 

 fine sieve, and the larger pieces ground in a coffee-mill. The whole 

 powder was carefully sifted and stored in a bottle. In the case of tara- 

 kihi 1 and mullet 1 further oxidation of the fat was noticeable in that 

 part exposed to the light. 



(II.) Percentage of Water and Solids. 



This was carried out in a hot-air oven at 65°-70° C, the average of 

 three estimations per sample being taken. 



(III.) Percentage of Protein. 



The total nitrogen was estimated on fresh material by the Kjeldahl 

 method, 0*2 N solutions of acid and alkali being used. The protein was 

 calculated as total nitrogen multiplied by 6-25, and the average of two 

 estimations per sample taken.* 



(ly.) Percentage of Fat. 



The dried powder from (I) was extracted with sulphuric ether in a 

 Soxhlet extractor. After twelve hours' extraction the solvent was evapo- 

 rated somewhat, the mixture filtered, the remainder of the ether carefully 

 evaporated, and the oil finally dried for three hours or more at 52° C. 

 The figure in the tables is the average of two estimations. (The water 

 percentage of the powder was estimated, to obtain the amount of fresh 

 material represented.) 



(V.) Percentage of Ash. 



This was carried out in the usual way with the dried material from (II) 

 in a Davy's crucible furnace. The longer method of extracting the chlo- 

 rides with distilled water after the first charring, and adding the residue 

 after evaporation to the ash, was used at first but discontinued, as the 

 results from the shorter method were found to vary but little from those 

 of the longer method, and the greater accuracy seemed unnecessary, as the 

 protein and fat estimations could only be approximate. 



(VI.) Calculations. 



■ From these results the following figures were calculated : — 

 (1.) Calories per cent., using the factors 4-1 large calories per gramme 



of protein and 9-3 large calories per gramme of fat. . 

 (2.) The cost of 1,000 calories, and of 100 grammes of protein. 

 (3.) For purposes of comparison the composition of milk, meat, and 



eggs was taken as given in Hutchison's Food and Dietetics. 



Results. 

 The results are shown in, the following tables (I-VI). 



* The use of this figure (6-25) is not quite satisfactory, as the proper factor to use 

 with fish proteins requires investigation. 



