Common Forcing Pump.
263
Chap. 3.]
The ordinary forcing pump has two valves, as in the annexed figure,which represents it as generally made. The cylinder is placed above thesurface of the water to be raised, and consequently is charged by the pres-sure of the atmosphere ; the machine, therefore, is a compound one, dif-
fering from that last described, whichis purely a forcing pump, the water en-tering its cylinder by gravity alone.The action of the machine now underconsideration is similar to that of thesyringe: when the piston is raised theair in the pipe below the cylinder rushesthrough the valve and is expelled onthe descent of the piston through dieother valve in the ascending or dis-charging pipe; and on a repetition ofthe strokes of the piston, water rises inthe suction pipe, enters the cylinder,and is expelled in the like manner.Pumps of this kindare sometimes placedin the yards of dwelling houses, thesuction pipe extending into a well, andthe ascending one to a cistern in theupper parts of the building. In thesecases a cock is generally inserted a lit-tle above the valve in the ascendingpipe to supply water if required in thevicinity of the pump.
The beautiful instrument used of late years to transfer liquids into andfrom the human stomach is a modification of the above machine. It cannotwith propriety be named a syringe, for as it is furnished with valves, it is,in every respect, a pump. Having been employed with much success inwithdrawing poison from the stomach, it is now justly classed among theessential apparatus of the surgeon. Its origin and history are detailed ina pamphlet published by its inventor, Mr. John Read, of England, whodevised it in 1819, and in the following year obtained a patent for it underthe name of a “Stomach and Enema Pump.” After visiting London twice in vain for the purpose of procuring suitable tubes, he tried to getsome made in the country, but failed. On a third visit to the metropolishe obtained an indifferent one which he thought might answer, and afteradapting it to a pump, “ I then [he observes] presented it to Sir Astley Cooper , who asked me for what purpose it was intended ; I told him itwas intended for the removal of fluid poisons from the human stomach;after a few minutes inspection of the instrument, Sir A. made the follow-ing reply :—‘ about three weeks ago I was called to attend a young ladyabout 10 o’clock in the morning who had taken opium; I gave her sul-phate of copper, sulphate of zinc and other things: I sat by her untileight in the evening, when she died ! If I had been in possession of thisInstrument at the time, I could have relieved her in five minutes, and havesaved her life.’ After many questions how I came to think of such athing, which I satisfactorily explained, he said ‘ what can 1 do for you Vmy answer was—the publicity of your opinion is all I wish : he replied,‘ that you shall soon have and he ordered me to meet him the next dayat G-uy’s Hospital at one o’clock, when he proposed to try an experimenton a dog; but as no dog could be procured, [that day,] Sir Astley pro-posed Friday at the same hour; when I attended as before, and a dog
No. 118. Common Forcing Pump.