SEA-FISHERIES LABORATORY. 217 



difference. The bottle with its contents was now dried, in 

 the water oven until the weight was constant, a matter usually 

 of about 20 hours, or more. The fat was then extracted. 



In the richest samples the oil oozed out through the 

 thimble in the process of drying, and it was necessary to rinse 

 out the weighing bottle, adding the solvent to the extraction 

 flask. It was also necessary to plug the opening of the thimble 

 lightly with dry cotton wool to prevent the breaking away of 

 small fragments of the dried tissue and the entrance of these 

 into the extraction flask through the siphon tube. In 

 extraction the flask and Soxhlet were wrapped round with a 

 towel so as to keep the temperature of the solvent as high as 

 possible — it could almost be made to boil in the Soxhlet by 

 this method. Extraction was usually carried on for two or 

 three hours by which time all the fat was removed. Indeed 

 after the third siphoning all the colour had usually disappeared 

 from the solvent in the Soxhlet. 



The flask containing the solution was then detached and 

 the solvent distilled away. The flask was then dried in the 

 steam oven till its weight was constant. This process was 

 hastened considerably by frequent blowing into the flask by 

 means of a small hand bellows. The heavy vapour of carbon 

 tetrachloride was thus removed. As a rule constancy of 

 weight was attained in about 8 to 10 hours. Checks on the 

 accuracy of the analyses were made by drying and weighing 

 the residues. The latter were also stored in order that Kjeldahl 

 nitrogen analyses might be made, but no time was available for 

 this latter work. The error in the analyses is, I think, fairly 

 small ; and when the individual differences of fish and fish 

 are considered it may be concluded that further refinements 

 in the methods of estimation would be futile. 



The results are given in tables I to III. From the dates 

 of the analyses the samples can be identified, and a comparison 

 with Mr. Riddell's results (published in this report) can be made. 

 The degree of ripeness of the fish and the relation of the sample 



