2 INTRODUCTORY— THE CONSTITUENTS OF MILK. 



It exists in milk in tlie form of small globules. Many have 

 thought that a true membrane surrounds each globule, and 

 Bechamp considers this view as proved by the behaviour ot 

 milk when treated with ether. He finds that milk is capable ot 

 dissolving a very large quantity of ether, much more than woiild 

 be dissolved in the aqueous portion of the milk, and he explains 

 this by the theory that the ether is dissolved by the fat con- 

 tained in the membranes. His theory assumes that the ether 

 has passed into the membrane by the process known as " endos- 

 mose," and that the endosmose is stopped only when the pressure 

 exerted by the distended membrane is equal to the osmotic 

 pressure ; "the presence of fat to small amount in the excess of 

 ether which separates is explained as partly due to a process 

 of exosmose of the fat within the membrane concurrently with 



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Kg. 1.— Fat Globules in Milk. 



the endosmose, and partly to the bursting of a number of the 

 globules. The opponents of his theory urge that the amount 

 of fat in the excess of ether which separates, if this be great, is 

 too large to be explained by assuming exosmose, or the bursting 

 of the globules, which should not take place to a greater degree 

 with a large excess of ether than with a small. 



Storch has put forward the view that no real membrane exists 

 round the fat globules, but that a gelatinous "mucoid" mem- 

 brane {slim-memhran, in Danish) surrounds them ; this consists, 

 according to him, of a combination of 6 parts of a " mucoid " 

 protein with 94 parts of water (menibran-slim). He bases his 

 view — 



(1) On the fact of the existence of this mucoid substance in 



