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ficial emulsions behave in the same way when treated with ether, 
and in this case there can certainly be no membrane to protect 
the fat. Ifthe effect of the addition of a little alkali or acid is due 
to the solution of a membrane, why should alcohol, which hardens 
all tissues, certainly does not dissolve them, act in the same way. 
The fact is that any substance that destroys the emulsion will have 
the same effect. If in the preparation of an emulsion, a highly col- 
ored oil, such as compose the prepared butter colors, is used instead 
of a colorless one, and the emulsion when formed shaken with ether, 
the globules of the mixture produced will appear under the rzicro- 
scope more or less colored, according to the amount of ether taken, 
showing that the colored fat has been dissolved in the ether. 
Not only have milk and artificial emulsions behaved alike in re- 
spect to the points mentioned above, but the resemblance has been 
equally marked in all others to which our experiments have been d1- 
rected, so that the conclusion seems inevitable that milk itself is an 
emulsion. But there are a few observers who think they have seen 
these membranes, and to them the evidence which these analogies 
present is inconclusive. While acknowledging the greater weight 
which direct vision should have, still, in consideration of the uncertain- 
ty which always attends such observations, and the failure of others 
skilled in the use of the microscope to confirm them, coupled with 
the fact that under the most favorable circumstances the number 
seen has been very small compared to the immense number of glob- 
ules which must have been present, it seems probable that some ab- 
normal appearance, or foreign matter in the milk has been seen and, 
through the influence of a preconceived opinion, supposed to be the 
broken sacks which had contained the fat. 
This subject has been treated at considerable length because it has 
a practical bearing upon the butter industry. If it is true that milk 
is an emulsion, or even in most of its properties behaves like one, we 
have a ready means, in artificial emulsions, of testing certain ques- 
tions which with a complex substance like milk are difficult or even 
impossible of solution. It also modifies to a certain extent our ideas 
concerning the best methods of churning, and helps to explain why 
some give better results than others. Experience has done much 
toward determining the best methods, and has brought about many 
changes which have had a marked influence on the quantity and 
quality of the product. But these changes, as shown in the develop- 
ment of the churn, have been steadily in a direction which the sup- 
position that milk is an emulsion would demand. A few years ago 
most of the new churns put upon the market consisted of complex 
arrangements of floats for the purpose of beating and agitating the 
cream in the most violent manner possible. Now however the churns 
used by the most successful manufacturers contain no floats, and even 
have the angles modified so that rubbing or grinding of the globules 
except upon each other is reduced to a minimum. 
The former churn is precisely what is required to rupture the mem- 
branes, if they exist, and set the fat free; but is not consistent with 
the idea of an emulsion. Have the dairymen made a mistake in the 
quite general adoption of the simpler churn? I think not, and trust 
that experiments about to be made will furnish information which 
