Hydraulics,

3

6

is shorter and the Bore larger. On the.contrary, if a Pipe be inserted perpendicu-larly

Force of Resilition in the Blood spouting from Veinsand Arteries in Bleeding; the Force by which theChyle ascends from the Receptaculutn by the Thoracic.Duct to the Left Subclavian Vein, or by which theBlood ascends from the lowest Parts of the Body to theHeart. In short, nothing in the Animal Oeconomy canbe well understood but by an Acquaintance with theHydraulic Laws of Fluids : For an animal Body is themost curious and compounded Hydraulic Machine inNature.

10. A signal Example of the Use of Hydraulics in thisRespect I shall produce from the admirable Experimentof Dr. Hales in his Hamajlatics. The Doctor causeda Mare to be tied down alive, and laid open the LeftCrural Artery, in which he inserted a Brass Tube, andon that fix’d a Glass Tube; and then cutting the Liga-ture on the Artery, the Blood rose in the Tube in anInstant about 4 Feet, and continued to rise till it attain-ed the Height of 8 Feet and 3 Inches. In a Geldinghe tried the same Experiment, and the Blood rose tothe Height of 9 Feet 8 Inches : This was in the fameArtery as before. In another Mare he fix’d a Pipe andT ube into an Incision of the Left Jugular Vein, and theBlood rose to 4I Feet; and then he fix’d it in the LestCarotid Artery, where the Blood rose to 9 Feet and6 Inches. In an Artery of a Doe it rose to 4 Feet 2Inches ; in a Dog, to 6 Feet 8 Inches ; in a Sheep,to 6 Feet 51 Inches ; and he conjectures that it wistvery probably rife in a Man to the Height of 7 Feet and6 Inches.

11. Now to estimate the Force with which the LeftVentricle of the Heart (of the first Mare) propell’d th®Blood, the Doctor found by means of injected WaX,that the Capacity of the Ventricle was 10 Cubic Inches,and the Surface on the Inside was equal to 26 Squai' eInches ; also the Area of the greatest Section of th® .Ventricle from Apex to Base was 6,83 Square Inches tConsequently the whole Pressure upon the internal Sur-