22 MILK [in 



But all these seemingly plausible arguments in 

 favour of the existence of a membrane can be easily 

 explained on grounds which do not require the 

 assumption of a membrane. In the first place, the 

 difficulty of obtaining milk-fat free from albuminous 

 matter is due simply to the fact that minute 

 quantities of these bodies cling to the fatty globules, 

 and, although not forming any solid membrane, may 

 yet form a thin liquid envelope. Again, the isolation 

 of the fatty globules, although not so easily explained, 

 does not need the supposition of a membrane. It 

 may be explained by the semi-solid condition of the 

 casein and of a part of the mineral matter. According 

 to Babcock, milk, after being kept for a short time, 

 has formed in it a body resembling blood-fibrin. 

 This body has the effect of rendering the milk less 

 limpid, and at the same time helping to prevent 

 coalescence of the globules. A further argument in 

 support of the membrane theory is based on the 

 behaviour of milk towards ether, which, it is well 

 known, is an excellent fat solvent. If milk be 

 shaken up with ether, it is found that the ether 

 does not dissolve out the fat globules, as is proved 

 by the fact that there is no diminution in the opacity 



point of water, is afforded by submitting them to microscopic 

 examination, when it will be seen that they maintain their globular 

 form. On solidifying them at a considerably lower temperature, 

 however, they will be seen to lose their globular form and assume 

 different shapes, due to solidification. 



