36 SECTIONAL ADDRESSES 
a picture illustrating similar experimental conclusions as to how more 
than two such sugar units are united in the various forms of carbo- 
hydrates. Without giving the intimate experimental basis for these 
conclusions, I may here show how two molecules of cellobiose are united 
in a continuous chain of such units in cellulose, and how maltose units 
are assembled in starch. Let us envisage this process, repeated by 
Two maltose units assembled Two cellobiose units assembled 
as in starch. as in cellulose. 
adding still more maltose units or cellobiose units to our lengthening 
chain and we approach to the constitutional picture representing starch 
and cellulose. Striking as the statement may appear, it is nevertheless 
the case that these two models are structurally identical. They owe 
their differences to the varied stereochemical forms of the same gluco- 
pyranose units which are found to be those of «-glucose in maltose and 
6-glucose in cellobiose. Arranged as a continuous chain, it will be found 
that the models present a perfectly symmetrical picture in the case of 
cellobiose, showing the sixth carbon atom or side chain of each hexose 
residue alternately above and below in the picture, whereas, in the case 
of continuous units of maltose assembled in a chain, this sixth carbon 
atom occurs entirely on one side: a representation less symmetrical than 
that of cellobiose. Moreover, the continued repetition of «-gluco- 
pyranose units in the starch complex, represented by assembling numerous 
maltose residues, provides a model which departs markedly, in zig-zag 
or spiral fashion, from the more or less straight line which is furnished 
by the continuing units of cellobiose in cellulose. And so, as Milton 
puts it : 
“with many a winding bout 
Of linked sweetness long drawn out,’ 
we picture the sinuous track of glucose units assembled in the continuous 
chain of the starch molecule. This circumstance appears to account for 
the difficulty of obtaining a regular pattern for starch which marks the 
X-ray diagram obtained for native cellulose. It will be seen that not 
only does the cellobiose picture, as determined by the classical constitu- 
tional methods of organic chemistry, fit perfectly into the size of cell 
