The Heart As A Machine

The heart is probably the most efficiënt jiece of physioal apparatus known. From i purely inechanicul point ol view it issomching like eight times a-; efficiënt as the best team engine. It may Le depcribed, nichanically, as little more tban a doublé force )ump, f'urnished with two reservoir and ;wo pipea of ouifluw ; atid the niain probem of its action is bydro-dynaniical. The eft ventricle lian a capacity of about three Minees; it beat 75 times a minute; and :he work done in overcoiuing the resistance )f the circulating fystem is equivalent to iftinjj its charge ol'a little short of ten feet 9.923 ft.) The average weight of the heart ,8 a little under ten ounces (9.39 oz.) The iaily work of the left ventricle is, in round Dumbers, ninety foot tons ; adding the work jf the right ventricle, the work of the entire srgan is nearly one hundred and twentySvefoot-tons. The bourly work of the heart iccordingly equivalent to lifiing itself 20,000 feet an hour. An active mountain climber can average 1,000 feet of a? cent an hour, orone-twentieth of the work of the heart. The prize Alp engine" Bavaria" lifteditsownweight ,7u() teet mi hour, thus demonstiating nnly one-eighth the efliciency of the heart. Four elements have to be considered in estiniating the heart's work : (1) the statical pressure of the blood column equal to the animal's height, which hasto besustained; (2) the force consumed in overcotuing the inertia of the blood-viiijs ; (3) the resistance offered by the capillary vessels; (4) the I'riction iu the heart k-elf. This is, in a state of health, kept at it.s minimum by the lubricated serous meuibrane of the