at and wheat flour, and the various modes of
determining their nutritive value_.--In my former report it was
stated that the analyses of the various samples of wheat, the
results of which were there given, had been chiefly directed to the
determining the amount of rough _gluten_ which they contained. My
reasons for adopting this plan, and the arguments in favor of its
general accuracy, as compared with other modes of analysis, and
especially that by which the ultimate composition is ascertained,
were also detailed. A more full examination of this subject has
served only to strengthen the opinion already expressed, that for
the great purpose to be answered by these researches, the process
which I have adopted is, to say the least, as free from objection
as any other, and if carefully and uniformly carried out, will truly
represent the relative values of the several samples of wheat flour.
As this is a matter of much consequence in a practical point of
view, I trust I shall be excused for introducing some additional
facts in regard to it.

The term _gluten_ was originally applied to the gray, viscid,
tenacious, and elastic matter, which is obtained by subjecting wheat
flour to the continuous action of a current of water. But it appears
that this is a mixture of fibrine and caseine, with what is now
called _glutine_, and a peculiar oily or fatty matter. Now these
substances may be separated from each other, but the processes
employed for this purpose are tedious, and to insure accuracy the
various solvents must be entirely pure--a point which, especially in
the case of alcohol and ether, is not ordinarily easy to be
attained. This will be rendered still more evident by a reference to
a French process, which will hereafter be noticed.

But were it much less difficult in every case accurately to separate
the constituents of gluten, it would not, in my opinion, be of the
least practical utility. It is to the peculiar mechanical property
of this gluten that wheat flour owes its superior power of detaining
the carbonic acid engendered by fermentation, and thus communicating
to it the vesicular spongy structure so characteristic of good
bread.[37] It may also be added, that the results of more than one
hundred trials have satisfied me that a diminution or loss of
elasticity in the glute