Which statement is true regarding blood transfusions? Blood transfusions were common practice in the seventeenth century. They routinely infused human blood into animals. Blood transfusions were performed by infusing sheep's blood into humans; in the eighteenth century, they were common and highly successful. In the seventeenth century, blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century. A blood transfusion is a lifesaving procedure that was developed and perfected in the nineteenth century.