Experimental psychology and its bearing upon culture . the plethysmograph or (savethe mark!) sphygmoplethysmograph (Fig. 56) we getnot only the pulse, but the changes in the generalvolume of a limb. The principle here applied is asold as Archimedes — that if anything is immersed inwater, the level of the water will rise according tothe volume of the object we put into it. If we en-close the forearm, for instance, within a glass cylin-der, and, through a small opening at the top, likethe neck of a bottle, pour in tepid water until thecylinder is full, the height of the water in this open-ing is
Experimental psychology and its bearing upon culture . the plethysmograph or (savethe mark!) sphygmoplethysmograph (Fig. 56) we getnot only the pulse, but the changes in the generalvolume of a limb. The principle here applied is asold as Archimedes — that if anything is immersed inwater, the level of the water will rise according tothe volume of the object we put into it. If we en-close the forearm, for instance, within a glass cylin-der, and, through a small opening at the top, likethe neck of a bottle, pour in tepid water until thecylinder is full, the height of the water in this open-ing is found to vary from time to time, according tothe mental state of the person whose arm is in thevessel; and, by means of a simple pneumatic contri-vance, these changes of the waters level can be madeto write their own record on a sheet of moving this way we get a somewhat compHcated line,every rise of which denotes that the arm at thatmoment expanded, while a fall implies that its volumediminished. In the accompanying record (Fig. 57) the. Fig. 55. — Sphygmograph.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectpsychol, bookyear1903
