All these animals lived side by side during the greater part of the quaternary period. They afterwards became by degrees either extinct or separated. At the commencement of the present period, France, in which at one time they were all to be found, only retains the horse; and we must admit further, with M. Toussaint, that our beasts of burden and draught, are descended from fossil species, an opinion which is far from universal amongst palæontologists. We may remark in passing, that the same uncertainty exists upon the subject of the spotted hyæna and the grizzly bear, regarded by some palæontologists as _races_ referable to the cave species. Man was, in Europe, the contemporary of all these species. The phenomena which have given to these countries their latest characters, have not always had the same violence, nor have they either commenced or terminated abruptly. They offered periods of repose and of relative activity, till the time when the continents assumed their definite proportions, when the glaciers were first confined within their present limits. The modifications of living beings accord with these oscillations of the inorganic world. The principal animal species seem to predominate in turn; the human races appear in succession, increase and decline. During the deposition of the _lower alluvium_ (bas niveaux) of our valleys, the mammoth, rhinoceros, and great carnivora, seem to have played the principal part. Man disputed the ground with them, and fed upon their flesh. The struggle against the conditions of life, and the wild beasts of the ancient world was terrible. The race of these primitive times bears in a high degree the mark of this savage nature. During the period in which the _mean inferior alluvium_ (_moyens niveaux inférieurs_) were formed, the great animal species still inhabited the whole of Europe. The number of their representatives seems, however, to be diminishing; less formidable species begin to multiply, and the horse, in particular, forms, at least in places, large herds, which offered an abundant source of nourishment to man. The latter was represented especially by a race endowed with remarkable aptitudes. At first, we find it struggling with as much vigour as the preceding one, and under almost identical conditions; but, by degrees, perfecting all its methods of action, and adapting them to the new conditions introduced by the advance of time.