Historian Webster Tarpley has done some extensive research on the history of the Venetians - their philosophy, the creation of the Order of Jesuits, their infiltration into the Royalty in Europe and their effect on other aspects of history in the rest of the world.
Tarpley touches on this in one of his interviews with Alex Jones concerning Climate-gate (video below)...
"It’s the mentality of the Venetians in this sense:
Back in the 1200 & 1300s, the Venetians, and the Genoese & certain other banking centers, were lending money to the crown heads of Europe. And they were imposing levels of interest (usuary) that forced the kings & the rulers to increase the tax burden on the peasantry of Europe so they got less & less to eat, and that meant that they were visited by malnutrition and all kinds of diseases that accompany that. By the time the contagion arrived, presumably from the Far East, of the Black Death, there were no natural defenses left., and the epidemic had free reign. That killed about a third of the population of Europe."