150 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



dried and weighed, the date of the sample having been written 

 in pencil on the thimble to avoid confusion. Mussel powder 

 was wrapped carefully in the filter paper and placed in the 

 thimble, the latter being then plugged by the cotton wool. 

 It was found in practice that this method prevented a passing 

 over of the powder itself during the extraction. The weighing 

 bottle, with its contents, was placed in the oven, and once a 

 constant weight was obtained the amount of powder in the 

 thimble was ascertained by subtracting the original weight 

 of the bottle, etc. 



To ensure as complete an extraction as possible, the Soxhlet 

 apparatus was kept working for three or four hours, although 

 the solvent appeared clear after the third or fourth siphoning. 

 The thimble, with its residue, was then placed back into the 

 weighmg bottle and dried in the oven. The weight of the 

 residue was a check upon the accuracy of the extraction, since 

 its weight plus that of the carbon tetrachloride extract should 

 equal the original dry weight of the powder taken for the 

 experiment. The error generally fell to within 0-5 %, and 

 where differences were greater, the extraction was carried out 

 again. 



This system of fat extraction is not without error ; other 

 substances besides fats are probably extracted from the tissues. 

 Moreover, there will be oxidation of some of the fat present 

 in the powder during the heating and drying process. The 

 proprietv of estimating fats in such a manner, instead of 

 estimating them as fatty acids, has been discussed by several 

 writers*. 



The results from the above methods, however, if not 

 strictly accurate are all obtained under the same standard 

 conditions ; and since this work is one of comparison rather 

 than intensive quantitative estimation, it is sufficient for the 



* For papers see Hartley, J. of Physiology, 1907-8 ; Mottram, ibid,, 

 1909-10 ; Kumagawa and Suto, Bio -chemical Zs., 1908 ; Tamura, ibid,, 

 1913. 



