Foucault gave numerous examples of biopolitical control when he first mentioned the concept in 1976. These examples include "ratio of births to deaths, the rate of reproduction, the fertility of a population, and so on." He contrasted this method of social control with political power in the Middle Ages. Whereas in the Middle Ages pandemics made death a permanent and perpetual part of life, this was then shifted around the end of the 18th century with the introduction of milieu into the biological sciences. Foucault then gives different contrasts to the then physical sciences in which the industrialisation of the population was coming to the fore through the concept of work, where Foucault then argues power starts to become a target for this milieu by the 17th century. The development of vaccines and medicines dealing with public hygiene allowed death to be held (and/or withheld) from certain populations. This was the introduction of "more subtle, more rational mechanisms: insurance, individual and collective savings, safety measures, and so on."