THE COCOA TREE AND ITS FRUIT. 19 



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carmine or violet color, and are distinguished by the change of shade 



when an alkali is added, becoming thereby darker. 



These are the only structural elements which a pure powder or paste 

 of chocolate should show under the microscope. Any other substances 

 must be recognized as accidental or intentional additions. 



All seeds of whatever kind contain, as a part of their substance, the 

 matter of which cell walls are made, namely, cellulose. The percent- 

 age differs in different seeds, in those of the chocolate plant being 

 about three in the hundred. Cellulose has the same chemical composi- 

 tion as starch, but its physical properties are not the same as those of 

 starch; among these may ife mentioned its entire insolubility in boiling 

 water, whereas starch readily dissolves. 



Starch forms, on an average, 8 to 10 per cent, of chocolate seeds. 

 It consists of minute spherical grains, not distinguishable from that 

 found in many other kinds of seeds. Traces of gum and of other 

 allied bodies are alst> present in the seeds. 



Albuminoids, or substances resembling, in a general way, the albu- 

 men of egg, occur in chocolate seeds as they do in other seeds, and in 

 a somewhat higher amount than in certain other cases in which seeds 

 are used as food. The percentage ranges from about 15 to 20, depend- 

 ing on the variety. These albuminoids are compounds of nitrogen, 

 and are extremely nutritious. In the seeds they occur in a readily 

 assimilable form, fit for digestion. 



Cacao red occurs as a coloring matter in small amount. It is ren- 

 dered dark by alkalies. 



Theobromine, the active principle of the cocoa bean, constitutes less 

 than i per cent, of the weight of the seeds, but it varies greatly in 

 amount in different seeds, ranging from %oo of i per cent, in some to 

 a trifle over i per cent, in others. 



The ash left, on completely burning cocoa beans, is not far from 

 4 per cent. Its composition is substantially that of the ash of seeds of 

 other plants. 



