70 PROCEEDINGS OF SECTION B. 



5.— THE ESTIMATION OF FAT. WITH AN IMPROVED METHOD FOR 

 THE DETERMINATION OF FATTY ACIDS AND CHOLESTEROL 

 IN TISSUES. 



By E. C. GREY, B.Sc, Acting Assistant Lecturer and Demonstrator in Physiology in the University 



of Sydney. 



The gradual discovery of the phosphorised and nitrogenous fatty 

 substances, spoken of collectively as lipoids, has of recent years very 

 considerably modified our conceptions of the nature of the fats 

 which build up the tissues of our bodies, and although to the physio- 

 logical chemist these conceptions are tolerably familiar, they do not 

 seem yet to have been much recognised or utilised by those who are 

 devoted to applied science. For this reason one sees still employed 

 the old methods of ether extraction. Two assumptions are involved 

 in this method, firstly, that ether is capable of dissolving all the fat 

 from tissues, either vegetable or animal, and secondly that whatever 

 does dissolve in ether is indeed to be considered fat. As a matter 

 of fact both these assumptions are incorrect. 



Dealing firstly with the question : Does ether extract all the 

 fat from tissues ? If the tissue is moist, the extraction is very 

 laborious and incomplete. After 200 hours' extraction with Soxhlet 

 apparatus, Dormeyer was able by his method ^ to demonstrate 

 that 8*5 per cent, of the fat still remained unextracted. To over- 

 come the difficulty, Voit - extracted the tissue with ether in 

 Soxhlet apparatus after he had previously dehydrated it with 

 alcohol. Under these circumstances, if care were taken to exclude 

 moisture, he found that only a trace of fat remained after 24 hours' 

 extraction. This result, however, would not have been so favour- 

 able if he had used other tissues than those which he employed. 

 Moreover, this author found it necessary to work with very small 

 amounts of material, so that the constants of the fat could not 

 readily be determined. 



A method of extraction is therefore desirable which yields the 

 fats in sufficient amount to permit of purification and examination. 

 Kumagawa and Suto (3) have recently examined at some length 

 the solvent powers of ether, petroleum spirit, benzene, ethyl alcohol, 

 etc., and have agreed in the opinion formed by most workers of 

 recent years that ethyl alcohol is the best fat-extracting solvent 

 for tissues. In many cases, however, the alcohol cannot dissolve 

 all the iatty material and the alcohol extraction must be followed 

 or preceded by treatment with ether. 



According to the method of Rosenfeld * treatment with hot 

 alcohol, followed by chloroform and petrol spirit gives also good 

 results, leading in many cases to complete extraction. For a 

 summary of these methods the reader is referred to Glikin's paper^ 

 and also to his article oi; fats.^ 



The second question concerns the nature of the material which 

 is extracted by any of these processes. During the early part of 

 the operation it is very probable that pure fats will be extracted 

 if the organ is rich in such, but later it will invariably be found 



