As far back as the mid-Seventeenth Century, physicians attempted blood transfusions, albeit only in extreme circumstances. The earliest attempted transfusions employed animals as the donors. Later, in the Nineteenth Century, blood was usually transferred directly from a healthy individual to a patient through a rubber tube with hypodermic needles at each end. Physicians were perplexed by the seemingly random results. Some transplant recipients survived while many others did not. The discovery of blood types in the early Twentieth Century is what finally led doctors to understand how transfusions could consistently save lives.