The experiments here detailed relate, in the first place, to the relative capacities of venous and arterial blood for heat; secondly, the comparative temperature of these fluids in different parts of the body during life is attempted to be ascertained; and thirdly, the author states those conclusions which he thinks may be drawn from his experiments. In his first experiments he endeavours to discover the relative capacities by the times of cooling equal volumes of venous and arterial blood, regard being also had to the specific gravities of each. When blood was taken from the jugular vein of a lamb, and after the fibrin had been separated from it by stirring with a wooden spatula, its specific gravity was found to be 1050, that of arterial blood from the same lamb, similarly treated, being 1047. The quantity of each taken for experiment was the same, contained in the same vessel, and heated to the same degree. An equal quantity of water in this vessel had cooled from 120° to 80° in ninety-one minutes; arterial blood cooled, through the same interval, in eighty-nine minutes; and venous blood in eighty-eight minutes: and hence the author infers the capacity of venous blood to be to that of arterial as 92 to 93⋅7, that of water being 100. By other experiments made on various mixtures of these fluids with each other at different temperatures, he estimates the proportion to be 93 to 93⋅7.