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XII. " On the Action of Bile upon Fats ; with Additional Ob- 

 servations on Excretine." By W. MARCET, M.D., F.R.S., 

 Assistant Physician and Lecturer on Chemistry to the 

 Westminster Hospital. Received June 10, 1858. 

 (Abstract.) 



Having formerly observed and communicated to the Soeiete de 

 Biologic of Paris, that by heating a solution of neutral tribasic 

 phosphate of soda (2NaO . HO . PO 5 ) mixed with animal fatty acids, 

 an emulsion was obtained attended with the formation of a small 

 quantity of soap, while no such action occurred if neutral fats were 

 used instead of fatty acids, I was induced to inquire into the nature 

 of the action of bile on neutral fats and fatty acids (sheep's bile being 

 used), with the final object of throwing, if possible, some additional 

 light on the digestion of fats. These investigations led to the fol- 

 lowing results : 



1 . A mixture of bile and neutral fats (stearine, oleine and marga- 

 rine), heated to a temperature above the fusing-point of the fat, un- 

 dergoes no change, and no chemical action takes place. 



2. A mixture of bile and fatty acids (stearic, oleic, and margaric 

 acids), heated to a temperature above the fusing-point of the fatty 

 acids, is transformed into a solution, a very few and minute globules 

 only of fat remaining unacted upon from the presence of oleic acid. 

 This solution becomes a perfect emulsion on cooling, and is attended 

 with a chemical decomposition of the bile ; and further, if the emul- 

 sion of bile and fatty acids be filtered when quite cold, and the residue 

 on the filter thoroughly washed with distilled water, the filtrate and 

 washings mixed together again possess the property of forming an 

 emulsion with another quantity of fatty acids, being also at the same 

 time partly decomposed, although in the previous operation the bile 

 appeared to have exhausted its power on the fatty acids. The fil- 

 trate and washings from this second operation again act upon a 

 fresh quantity of fatty acids, and so on ; only in every subsequent 

 operation the proportion of emulsion obtained appears to diminish, 

 and the induced chemical decomposition to be lessened. 



3. Pure oleic acid, when agitated with bile, cold or hot, produces 

 no emulsion or chemical action whatever. 



4. The stomach during digestion has the power of decomposing 



