489 



almond, and the kernels of stone fruits in general, comes 

 in contact with emulsin, another substance which they 

 invariably contain. On breaking the little cell walls, which, 

 in the natural state of the fruit, kept these substances 

 separated from each other, the contact of the two instantly 

 causes the elements of the araygdalin to arrange themselves 

 in new forms, so as to produce sugar, formic acid, oil of 

 bitter almond, prussic acid, and water; and thus, from a 

 substance perfectly harmless, are generated poisons of the 

 most deadly kind. Another curious change is communicated 

 to starch by the action of a peculiar principle, generated 

 during the germination of seeds, called diastase. When so 

 small a portion as one part of this substance is mixed with 

 a solution containing one thousand parts of starch, and kept 

 at a particular temperature, the whole is converted into a 

 solution of sugar in the space of a few hours. In this case 

 there is no exchange of elements between the diastase and 

 starch, no more than between the constituents of the almond; 

 it is the decomposing nitrogenous matters, namely, the emul- 

 sin and diastase, which, in both instances, suffice to induce 

 the change. In the same manner when we add yeast, a 

 substance in a state of rapid decomposition, to a solution of 

 sugar, we find the elements of the sugar dividing themselves 

 into two other compounds, namely, carbonic acid and alcohol, 

 without in any way sharing the elements of the yeast. Other 

 matters undergoing a similar kind of transformation to yeast 

 are capable of inducing a similar state of decomposition to 

 solutions of sugar ; but if the kind of transformation, as I 

 shall presently explain, be different, that is, if the compounds 

 it is producing be not the same as those produced by yeast, 



we shall have a different kind of decomposition induced in 



• • • . ^ 



the matters with which it comes in contact. The communi- 

 cation of putridity from one piece of dead flesh to another, 

 or from one piece of wood to another, are all instances of 



