directly
related to the actual configuration of the chemical units. But it
appears that we are barred from the present discussion of such a problem
in absence of any theory of the solid state generally, but more
particularly of those forms of matter which are grouped together as
'colloids.'

Cellulose is distinguished by its inherent constructive functions, and
these functions take effect in the plastic or colloidal condition of the
substance. These properties are equally conspicuous in the synthetical
derivatives of the compound. Without reference, therefore, to further
speculations, and not deterred by any apparent hopelessness of solving
so large a problem, it is clear that we have to exhaust this field by
exact measurements of all the constants which can be reduced to
numerical expression. It is most likely that the issue may conflict with
some of our current views of the molecular state which are largely drawn
from a study of the relatively dissociated forms of matter. But such
conflicts are only those of enlargement, and we anticipate that all
chemists look for an enlargement of the molecular horizon precisely in
those regions where the forces of cell-life manifest themselves.

The _cellulose group_ has been further differentiated by later
investigations. The fibrous celluloses of which the typical members
receive important industrial applications, graduate by insensible stages
into the hemicelluloses which may be regarded as a well-established
sub-group. In considering their morphological and functional
relationships it is evident that the graduation accords with their
structure and the less permanent functions which they fulfil. They are
aggregates of monoses of the various types, chiefly mannose, galactose,
dextrose, &c., so far as they have been investigated.

Closely connected with this group are the constituents of the tissues of
fungi. The recent researches of Winterstein and Gilson, which are noted
in this present volume, have established definitely that they contain a
nitrogenous group in intimate combination with a carbohydrate complex.
This group is closely related to chitin, yielding glucosamin and acetic
acid as products of ultimate hydrolysis. Special interest attaches to
these residues, as they are in a sense intermediate products between the
great groups of the carbohydrates and proteids (E. Fischer, Ber. 19,
1920), and their further investigation by physiological methods may be
expected to dis