664 THE AMERICAN JOURNAL OF SOCIOLOGY
both happy and unhappy. The comparative study of their social constitutions causes therefore the symptoms of health or of disease to be recognized, and, by consequence, the means of effecting a cure.
On the other hand, nations are composed not of individuals, but of families. The work of observation, which would be vague, undefined, and unable to lead to any conclusion if it had to be extended in one locality to individuals of different sex and age, becomes precise, limited, and conclusive as soon as it has for its object families. This is an evident fact ; it belongs to the very nature of that social unity of which the physical and moral organization of man furnishes the principle, and it is in this fact that the practical efficacy of the Le Play method of family monographs resides.
II.
1. Elasticity of the Le Play method. The application of the method of monographs does not require that the observer con- fine himself to one locality, to one class, or to one determined family. The principal advantage which it offers is that of per- mitting one to ascertain in a short time the customs of any country whatever. Not only is it not necessary to be located in that country, but one can even study it with success at a dis- tance if he has under his eyes a family that was born in it and lived in it for a long time.
Likewise one may observe indifferently any one of the agri- cultural or industrial classes of a locality. However, in a region which has not yet been described it is preferable to fix one's attention upon the peasants ; that is, upon the little agricultural proprietors who, with their families, employ upon their estate the whole of their time, without being obliged to work outside in the quality of hired persons. This class is always the fun damental element of a civilization. Thanks to the nature of its labors and habits, which result from the ownership of land, it preserves better than the others the imprint of the local genius.
2. Choice of the family to observe. In a determined class
