34 SECTIONAL ADDRESSES 
precise form constituting these complex carbohydrates is a fascinating 
experimental problem. Let us pass to consider the kind of atom model 
which must be ascribed to maltose, cellobiose, sucrose, and the relation- 
ship which these structural types bear to such important carbohydrates 
as starch, cellulose, and inulin. 
There are several ways in which two glucose units may be united 
through the intermediary of a common oxygen atom. Experimental 
work during the past twenty years has enabled us to proceed beyond the 
speculations of Fischer and to arrive at a precise picture for each of the 
disaccharides. The expressions C,H ,,0, + CgH 1.04 = CysHo901; + H,O 
merely indicate the union of two hexose residues with loss of water to 
give a biose. Of the several hydroxyl positions available for providing 
the point of union of two glucose residues it was found that it is those 
groups at the first carbon atom in one residue and the fourth carbon 
atom in a second residue which furnish the oxygen bond uniting two 
glucopyranose units in both maltose and cellobiose. 
¢ H,OH 
CH;0H 
Sore Ce) 
OH os ee 
veer - 
4 on 
Union of two B-Glucopyranose molecules. B-Cellobiose. 
It will be observed that in the latter formulations two 8-glucoses are shown 
united through two OH groups which are spatially above and below the 
planes of the pyranose rings. To bring the final cellobiose formula into 
alignment one of these rings is now inverted. It is of the highest im- 
portance to observe that although the units participating in the union of 
maltose are structurally identical with those assembled in cellobiose, 
yet these products are widely different in kind. The difference is entirely 
in the spatial arrangement of the left-hand components, indicated as 
«- or @-forms of glucose. It is this simple distinction which provides 
the reason for the different identities of starch, which is formulated on 
the maltose model, and cellulose, which is based on the formulation of 
cellobiose. There exist other polysaccharides in which the linking is 
different. This type may be illustrated by the assembly of two glucose 
