sion
of the plan of our work was to define these constituents by bringing
together all that had been established concerning them. These groups are
widely divergent in chemical character, as are the compound celluloses
in function in the plant. Consequently there is for each a special
method of attack, and it is a reversion to pure empiricism to expect any
one treatment to act equally on the pectocelluloses, lignocelluloses,
and cutocelluloses. Processes of isolating cellulose are really more
strictly defined as methods of selective and regulated attack of the
groups with which they occur, combined or mixed. A chemist familiar with
such types as rhea or ramie (pectocellulose), jute (lignocellulose), and
raffia (cutocellulose) knows exactly the specific treatment to apply to
each for isolating the cellulose, and must view with some surprise the
appearance at this date of such 'universal prescriptions' as the process
in question.

The third division of our plan of arrangement comprised the synthetical
derivatives of the celluloses, the sulphocarbonates first, as peculiarly
characteristic, and then the esters, chiefly the acetates, benzoates,
and nitrates. To these, investigators appear to have devoted but little
attention, and the contribution of new matter in the present volume is
mainly the result of our own researches. It will appear from this work
that an exhaustive study of the cellulose esters promises to assist very
definitely in the study of constitutional problems.

This brings us to the fourth and, to the theoretical chemist, the most
important aspect of the subject, the problem of the actual molecular
structure of the celluloses and compound celluloses. It is herein we are
of opinion that the subject makes a 'law unto itself.' If the
constitution of starch is shrouded in mystery and can only be vaguely
expressed by generalising a complex mass of statistics of its successive
hydrolyses, we can only still more vaguely guess at the distance which
separates us from a mental picture of the cellulose unit. We endeavour
to show by our later investigations that this problem merges into that
of the actual structure of cellulose in the mass. It is definitely
ascertained that a change in the molecule, or reacting unit, of a
cellulose, proportionately affects the structural properties of the
derived compounds, both sulphocarbonates and esters. This is at least an
indication that the properties of the visible aggregates are