INTRODUCTION TO SOCIOLOGY 619
stances which do not come exclusively from without. These latter substances are, on the contrary, manufactured in the body of the plant by the aid of more simple materials borrowed from nature. This is a new point of view which is destined to throw light on the sociological problem. The growth of the plant consists in the addition of a definite structure, as in the case of the crystal, but the plant grows by interior addition. One finds neither in the soil, nor in the water, nor in the air the compounds characteristic of the mass of the plant: albumen, gluten, starch, cellulose, and fatty matter. All the crude inorganic materials in them are furnished, however, by the atmosphere and by the soil : oxygen, nitrogen, carbonic acid, ammonia and water, argil and silica, lime, iron, potash, phosphorus, sulphur, etc. The plant divides all this primary material into different portions, in order to assimilate them, and to reunite them into new combina- tions at the interior of its structure-manufactory, where the new molecules distribute themselves among the old ones.
This is not all. In contrast with minerals, plants continue their development until a portion of their substance is detached in the form of seed or germ, and thus they reproduce their species. The same is true of the living animal. It is necessary, however, to note that most of the substances which the animal assimilates are provided directly by other animals and by plants. The animal also detaches a part of its substance, the egg, which gives birth to a similar animal.
The form of every animal and of every plant is, then, the product of the same relationships that we have indicated for the crystals. It results from the equilibration between two factors, the one internal, the other external. There is only this differ- ence : the equilibration is more complex. The internal factor adapts itself spontaneously to the more special conditions, from which results life.
Consequently, it is easy to understand that, in the inferior forms of life, the individuals are not distinguished from the species, any more than the crystals are. They have no individu- ality. Thus, in the kingdom of protista, intermediate between the vegetable kingdom and the animal kingdom, and including
