The regulations which attempted to confine the oppression of the Indians within bearable limits were persistently violated, not only by private individuals, but by the corregidors themselves. Kidnapping was reduced to a system, and often all the male adults of a village were dragged off to work in the mines, leaving only the women and children to till the fields. The corregidors went into partnership with merchants, and the poor Indians were compelled to purchase articles for which they had no use, and thrown into slavery to work out the debt if they failed to pay. The wiser viceroys did not waste their energies in vain efforts to mitigate the profitable abuses. They devoted their attention rather to the exaction of the last penny of taxes, to be spent in maintaining the horde of office-holders, or to be remitted to Spain. So rigidly was taxation enforced and so successful were the Spaniards in finding rich mines of silver, gold, and mercury, that early in the seventeenth century the revenue had reached the sum--enormous in those days of low prices--of nearly five hundred thousand pounds, of which about half was regularly sent to Madrid. Foreign nations could not effectively interfere with Spain's commercial and fiscal monopoly. The Isthmus was in her hands, and the voyage through Magellan's Straits or around Cape Horn was too stormy and uncertain for the slow, clumsy ships of that age, and only a few English and Dutch expeditions, half-trading, half-piratical, ravaged the coast towns in the seventeenth century. The most memorable event of Peru's history during the seventeenth century was the revelation of the sovereign virtues of quinine. The Lima physicians were unable to cure the Countess of Chinchon, the viceroy's wife, of a stubborn attack of malarial fever, but the rector of the Jesuit college had received some fragments of an unknown bark from a Jesuit missionary to whom they had been given by an Indian in the mountain wilds of southern Ecuador. Doses of this quickly restored the vice-queen, and when Linnaeus named the world's plants in scientific order, he called the genus to which the tree belongs chinchona, from the viceroy, through whom its virtues had come to notice.