310 MODERN SCIENCE READER 



Starch is an unsolved problem. It is of the highest im- 

 portance in Nature. Its wide distribution among plants 

 and the part that it plays as a constituent of foods show 

 this. What is it ? Of course, if we say it is a carbohydrate, 

 we have made the whole subject clear ! The truth is we 

 know very little about it, in spite of the large amount of 

 work that has been done on it. In what has been done 

 there is little promise of success, though the chemical 

 optimist hopes, even in the face of starch. I confess to 

 being a moderate optimist. If asked why I hope in this 

 case, I could only answer, "I hope that is all." 



Let us take the next step. This brings us to cellulose, a 

 substance of very great importance for all plants. It 

 forms, as it were, their skeletons. Just as animals are 

 built upon a basis of bone, so plants are built upon a basis 

 of cellulose. It is that constituent of plants that gives them 

 form and that enables them to resist the disintegrating in- 

 fluences to which they are subject in Nature. When a 

 piece of wood is treated with certain active substances, 

 " chemicals" as they are called by the outside world, many 

 of the constituents are destroyed and removed, and, finally, 

 what is known as wood-pulp remains. This is mainly 

 cellulose. As is well known, large quantities of paper are 

 made from this pulp. Paper is, in fact, more or less pure 

 cellulose. Every plant contains cellulose, and without it 

 the plants could not exist. It seems as though a chemist 

 ought to feel humiliated to have to confess that even less is 

 known about cellulose than about starch. There appears 

 to be some reason for believing that it is distantly related 

 to starch, but that is about all we can say. It is probably 

 enormously complicated. To be sure, it contains only the 

 three elements, carbon, hydrogen, and oxygen, but these 

 three elements can combine with one another in thousands 

 of different ways, forming, on the one hand, relatively 

 simple products, and, on the other, products of such com- 

 plexity that before them the chemist can only stand and 

 wonder. Cellulose belongs to the latter class. 



