These variations in the population of Europe have been attended with changes in distribution.  The centre of population has passed northward since the establishment of Christianity in the Roman Empire.  It has since passed westward, in consequence of the development of manufacturing industry.

We may now examine somewhat more minutely the character of the resistances which thus, for a thousand years, kept the population of Europe stationary.  The surface of the Continent was for the most part covered with pathless forests; here and there it was dotted with monasteries and towns.  In the lowlands and along the river-courses were fens, sometimes hundreds of miles in extent, exhaling their pestiferous miasms, and spreading agues far and wide.  In Paris and London, the houses were of wood daubed with clay, and thatched with straw or reeds.  They had no windows, and, until the invention of the saw-mill, very few had wooden floors.  The luxury of a carpet was unknown; some straw, scattered in the room, supplied its place.  There were no chimneys; the smoke of the ill-fed, cheerless fire escaped through a hole in the roof.  In such habitations there was scarcely any protection from the weather.  No attempt was made at drainage, but the putrefying garbage and rubbish were simply thrown out of the door.  Men, women, and children, slept in the same apartment; not unfrequently, domestic animals were their companions; in such a confusion of the family, it was impossible that modesty or morality could be maintained.  The bed was usually a bag of straw, a wooden log served as a pillow.  Personal cleanliness was utterly unknown; great officers of state, even dignitaries so high as the Archbishop of Canterbury, swarmed with vermin; such, it is related, was the condition of Thomas a Becket, the antagonist of an English king.  To conceal personal impurity, perfumes were necessarily and profusely used.  The citizen clothed himself in leather, a garment which, with its ever-accumulating impurity, might last for many years.  He was considered to be in circumstances of ease, if he could procure fresh meat once a week for his dinner.  The streets had no sewers; they were without pavement or lamps.  After nightfall, the chamber-shatters were thrown open, and slops unceremoniously emptied down, to the discomfiture of the wayfarer tracking his path through the narrow streets, with his dismal lantern in his hand.

Aeneas Sylvius, who afterward became Pope Pius ii., and was therefore a very competent and impartial writer, has left us a graphic account of a journey he made to the British Islands, about 1430.  He describes the houses of the peasantry as constructed of stones put together without mortar; the roofs were of turf, a stiffened bull’s-hide served for a door.  The food consisted of coarse vegetable products, such as peas, and even the bark of trees.  In some places they were unacquainted with bread.