THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



MAY 1879. 



XL V III. On the Formation of Emulsions, and the Action of 

 the Bile in Digestion. By Dr. G. Quincke*. 



1. Historical Review. 



AN emulsion consists of a large number of small spherical 

 globules of fatty matter suspended in an aqueous liquid. 

 Ordinary milk, for instance, is an emulsion. The smaller these 

 fatty globules the larger is their surface in proportion to 

 the mass, and the greater is the resistance they meet with 

 in ascending through the specifically heavier surround- 

 ing fluid. The smaller the fatty globules the longer they 

 remain suspended in the surrounding liquid, and the more 

 perfect is the emulsion. The minute globules have a con- 

 tinual tendency to coalesce into larger ones ; the less this 

 tendency and the smaller the uniform velocity of the ascent 

 of the globules in the surrounding aqueous liquid, the more 

 permanent is the emulsion. And the smaller this velocity the 

 less is the difference between the specific gravity of the emul- 

 sion and that of an actual solution of the fatty matter in the 

 liquidf. 



In chemists' shops an emulsion is made by diffusing mecha- 

 nically (rubbing with a pestle in a porcelain mortar) the glo- 

 bules of an oil throughout a solution of gum arabic in water. 

 In the process of digestion in the animal body the assimilation 

 of the fats is initiated by the formation of an emulsion in the 

 liquid contents of the intestine, and, as experience shows, faci- 



* From a separate impression from Pfliiger's Archiv fur die gesammte 

 Physiologic Translated by J. F, Iselin, M.A, 



t Camillo Bondy, Pogg. Ann. 1865, p. 323 ; E. Mach, ib. p. 329. 



Phil. Mag. S. 5. Vol. 7. No. 44. May 1879. 2B 



