Machina Carnis

The greater part of the eighteenth century brought no fundamental contributions to the elucidation of contractility in living organisms. A deeper understanding of the chemistry of inorganic and organic matter was really pre-requisite for this, and great strides now began to be made in these directions.

THE CHEMICAL BACKGROUND

The quantitative study of gases (which had begun with Robert Boyle in 1660) was continued vigorously during this next century, and interpreted in terms of the phlogiston theory of Stahl, enunciated in 1697. This theory explained combustion as due to the presence in combustible material of a principle of inflammability (sometimes credited with negative weight) termed phlogiston; material supporting combustion did so in virtue of its power to absorb phlogiston, and this principle was lost during combustion. The work of Black on fixed air (carbon dioxide) in 1755; of Cavendish between 1766 and 1784 on fixed air, inflammable air (hydrogen) phlogisticated air (nitrogen) and dephlogisticated air (oxygen); and of Priestley on dephlogisticated air may be specially mentioned. In 1774 Priestley prepared purified dephlogisticated air (to which Lavoisier a little later gave the name oxygen) by heating red oxide of mercury; he showed that this gas was better than common air for supporting combustion and life.

Lavoisier had also intensively studied calcination, and had shown that in this process tin for example gained in weight, while the air in which it was contained lost equally in weight and also diminished in volume.