The share which this cause had in the spreading of the plague over the whole earth was certainly very great; and the opinion that the black death might have been excluded from Western Europe, by good regulations, similar to those which are now in use, would have all the support of modern experience, provided it could be proved that this plague had been actually imported from the East; or that the oriental plague in general, whenever it appears in Europe, has its origin in Asia or Egypt. Such a proof, however, can by no means be produced so as to enforce conviction. The plague was, however, known in Europe before nations were united by the bonds of commerce and social intercourse; hence there is ground for supposing that it sprung up spontaneously, in consequence of the rude manner of living and the uncultivated state of the earth; influences which peculiarly favor the origin of severe diseases. We need not go back to the earlier centuries, for the fourteenth itself, before it had half expired, was visited by five or six pestilences. If, therefore, we consider the peculiar property of the plague, that in countries which it has once visited it remains for a long time in a milder form, and that the epidemic influences of 1342, when it had appeared for the last time, were particularly favorable to its unperceived continuance, till 1348, we come to the notion that in this eventful year also, the germs of plague existed in Southern Europe, which might be vivified by atmospherical deteriorations. Thus, at least in part, the black plague may have originated in Europe itself. The corruption of the atmosphere came from the East; but the disease itself came not upon the wings of the wind, but was only excited and increased by the atmosphere where it had previously existed. This source of the black plague was not, however, the only one; for, far more powerful than the excitement of the latent elements of the plague by atmospheric influences was the effect of the contagion communicated from one people to another, on the great roads, and in the harbors of the Mediterranean. From China, the route of the caravans lay to the north of the Caspian Sea, through Central Asia to Tauris. Here ships were ready to take the produce of the East to Constantinople, the capital of commerce and the medium of connection between Asia, Europe, and Africa. Other caravans went from India to Asia Minor, and touched at the cities south of the Caspian Sea, and lastly from Bagdad, through Arabia to Egypt; also the maritime communication on the Red Sea, from India to Arabia and Egypt, was not inconsiderable. In all these directions contagion made its way; and doubtless Constantinople and the harbors of Asia Minor are to be regarded as the _foci_ of infection; whence it radiated to the most distant seaports and islands.