the two valves; and the valve in the rear of the current now begun (the tricuspid) would open, and the water rush in to fill the vacuum in the india-rubber ventricle, to be again pressed forward by the next grasp of the hand; and thus--the fire (representing respiration) being kept up, and the alternate grasping and relaxing of the hand (representing the heart's regular impulse)--a perpetual circulation might be made to go on;[1] but not without another condition of the problem. And it was in performing this experiment that a truth was discovered, which, had it been known, many who have ignorantly lost their lives might have preserved them. When the fluid in the apparatus became equally, or nearly as much, heated at the extreme parts of the circulating tube as at the heating vessel, then the motive power of expansion ceased, and (the hand's impulse being too weak of itself to carry it on) circulation failed; but it was restored by putting snow or ice around the extreme parts of the tube. How often have we heard of ladies who, having gone into warm baths, have been found dead by their friends, or too nearly so, to be restored.[2] Through ignorance of the cause, no right means would be taken to restore them, such as dashing cold water upon the exterior, with simultaneous efforts to produce, in fresh air and in proper position, such artificial respiration as leads to the natural. Where no internal lesions have occurred, there is every reason to believe that such measures might produce restoration. My imperfect machines gave me to see how much might be done for this important part of physiology by a more perfect apparatus. Mine was merely horizontal--but one might be made to take as many positions as are natural to the human frame; and how many facts might such an one elicit concerning the effects of position on the circulation, by which lives might every day be saved! But skilful mechanicians, not ordinary mechanics, are needed, who are men of intellectual capacity, and are furnished with _carte-blanche_ for time and expense.[3]