Common country and common political institutions resulting as they do in common ideas, common interests and common habits, are the true source of national life; and as such of vast political importance. But they have small and sometimes no connection with the profound physiological questions of race and consanguinity; and from the physiological standpoint are of little count. It is not only possible that the most pure-blooded descendant of the Romans still existing may be some inhabitant of Treves or Marseilles; but it is more than possible that not one man or woman with the blood of the folk who founded the city on the Seven Hill exists among the herd who creep round the Capitol to-day. Languages, and the remnants of languages, in civilized or semi-civilized conditions, remain often in places where they arose, when the tribes of men who framed them have passed away; and except among purely barbarous nations, who exterminate all whom they subdue, a common language, or the absence of a common language, forms no criterion of blood relationships. The empty shell of a mollusc may lie on the spot where it lived long after the creature has died, or been eaten out of it; and he is an unwary naturalist who, picking it up, and finding it filled with the creatures who may have taken up their abode in it, imagines there is any necessary organic relation between the shell and its inhabitants. Like the unscientific naturalist, the popular mind is quite satisfied where it finds persons using a common language to suppose racial unity and descent; and, where there is no common language, the opposite; while these things often merely signify conquest or contact. Thus the nations of Europe are far more homogeneous from the physiological and racial standpoint than our sharply marked differences of language and political institutions would suggest.[35]