There arose a series of special laws to determine the status of laborers which became the basis of the great slave codes. As the free European white artisans poured in, these labor codes gradually came to distinguish between slavery based on race and free labor. The slave codes greatly weakened the family ties and largely destroyed the family as a center of government or of economic organization. They made the plantation the center of economic life and left more or less religious autonomy. They provided punishment by physical torture, death or sale, but they always left some minimum of incentive by which the slave could have the beginnings of private possession. In this way the economic organization was provided by which the middle classes of the world were supplied with a cheap sweetening material derived from sugar cane; a cheap luxury, tobacco; larger quantities of rice; and finally, and above all, a cheap and universal material for clothing, cotton. These were things that all men wanted who had anything to offer in labor or materials for the satisfaction of their wants. The cost of raising them was a labor cost almost entirely because land in America was at that time endless in fertility and extent. The old world trade therefore which sought luxuries in clothing, precious metal and stones, spices, etc., for the rich, transformed itself to a world-wide trade in necessities incomparably richer and bigger than its medieval predecessor because of its enormous basis of demand. Its first appearance was in the slave trade where the demand for the new American crops showed itself in a demand for the labor necessary to raise them; thus the slave trade itself was at the bottom of the rise of great commerce, and the beginning of modern international commerce. This trade stimulated invention and was stimulated by it. The wellbeing of European workers increased and their minds were stimulated. Economic and political revolution followed, to which America fell heir. New immigrants poured in. New conceptions of religion, government and work arose and at the bottom of it all and one of its efficient causes was the toil of the increasing millions of black slaves.