12 BUTTER-MAKING AND COMPOSITION OF MILK 



each fat-globule, cream should contain a higher percentage of 

 albuminoids than milk. This, Richmond maintains, is not so. 

 Dr. S torch concludes from extensive researches that there is a 

 gelatinous membrane enveloping the fat-globules. His conclu- 

 sions are based mainly upon the first three reasons given below. 

 The other facts mentioned also support his conclusions : 



(1) When milk has been stained with ammoniacal picro- 

 carmine, and the cream washed with water until it is free from 

 milk-sugar, a stained layer is present around each globule. 



(2) He has succeeded in isolating this gelatinous substance 

 from cream and butter. Owing to its existence in these two 

 substances, he assumes that it is also present in milk. 



(3) When ether is added to milk, the fat-globules .dissolve 

 with difficulty, unless some alkali is added to the milk first. 



(4) Bichamp maintains that when ether is added to milk 

 the fat-globules are enlarged due to the ether passing through the 

 supposed membrane by the process of osmosis. He considers 

 this fact sufficient to prove that there is a membrane encircling 

 each globule. 



(5) Butter containing 85 to 86 per cent fat is asserted by 

 Richmond to have the same consistency as cream containing 

 about 72 per cent fat at the same temperature. The solidity of 

 butter is due to the close proximity of the fat-globules. Now, if 

 cream with less fat has the same consistency as butter, the prox- 

 imity of the fat-globules must be equal to that of the butter; 

 this would indicate that there is a membrane and that this mem- 

 brane increases the size of the fat-globules. 



(6) The fact that cream separated by centrifugal force is 

 more easily churned than cream o*f the same richness separated 

 by gravity methods, would also be explained if the fat-globules in 

 milk had such a membrane surrounding them. 



This membrane, or what is believed to be a membrane, 

 Storch has isolated and analyzed. He finds it to consist of 

 94 per cent of water and 6 per cent of proteid. 



The reasons deduced by Storch are strong; and the behavior 

 of cream and butter renders it probable that there is such a 

 membrane enveloping each globule of fat. 



