The Polish students were eager to become acquainted with the new ideas, they absorbed them readily, and on their visits home or their final return they disseminated them in their own country. So great was the exodus of Polish students to German and other foreign universities, and so great the danger of infecting the country with the new religious doctrines and practices through the channel of intellectual intercommunication that the reactionary elements in the country found it necessary to force the king to pass laws forbidding the Polish youth to frequent foreign universities infected with heresy or suspected of such infection.[229] It is of great interest to note that in the sixteenth century Polish students were registered in considerable numbers in nearly every German and Swiss university of any consequence. They were at Wittenberg, Leipzig, Königsberg,[230] Frankfort on the Oder, Heidelberg, Herborn, Altdorf, Marburg, Freiburg, Würzburg, Dillingen, Mainz, Ingolstadt, Zurich, and Basel.[231] The German universities most largely attended by Poles were Wittenberg, Leipzig, Königsberg, and Frankfort on the Oder. The number of Polish students registered in these institutions of learning in the course of the sixteenth century was over two thousand.[232] At Heidelberg there were in the course of the century about one hundred and sixty-five Polish students,[233] at Altdorf, from its foundation in 1575 until 1617, two hundred and seventy,[234] at Marburg, from 1527 to 1628, about seventy,[235] and at Basel, from 1549 to 1570, also about seventy.[236] At Wittenberg we find representatives of prominent Cracow families among Luther’s students as early as 1520.[237] By the end of the same decade the number of Polish students in that university had considerably increased, and there were found among them Stanislaus Orzechowski, Stanislaus Warszewicki, I. Krotowski, I. Lipczyński, three Górkas, two Ostrorogs, Tomicki, and Grudziński.[238] After 1530 the sons of the Polish nobility flocked to Wittenberg in steadily growing numbers.[239]