The Romance of Modern Chemistry

 HHSHH CHAPTER III NATURE’S BUILDING MATERIAL •I J A COMMON way of classifying natural objects is suggested by the familiar questions—“ Is it animal ?11 “ Is it vegetable ? ” “ Is it mineral ? ” Now, although from the chemical point of view we are chiefly concerned with so-called “dead” matter, there are many things belonging to the animal and vegetable kingdoms which we must take into consideration. A certain object may be assigned to one of these two kingdoms, not because it is at present alive, but simply because at one time or another in its history it has been a part of a living thing, a plant or an animal. A bone, for example, would be considered to belong to the animal kingdom, although in itself it is as dead as a door-nail, apart from the living and throbbing body of which it was a member. A tree that refuses to become green under the touch of spring would still be regarded as “ vegetable,” although, so far as growth is concerned, it might as well be a block of granite. What makes all the difference between the mineral kingdom on the one hand, and the animal and vegetable kingdoms on the other hand, is the mysterious thing called “life,” not the mere materials of which the various objects are built up. It is no doubt true that the materials associated with plants and animals, and thus involved in the processes of life, are frequently of 28