Certain Molar Movements of the Human Body produced by the Circulation of the Blood.

A PERSON standing erect in a perfectly easy posture on the bed of an ordinary spring weighing-machine, and maintaining, as far as possible, perfect stillness, will be found, if the instrument is delicately adjusted, to impart a rhythmic movement to the index, synchronous with the pulse and according to the following rule:-At each occurrence of systole in the heart, the needle will be vigorously deflected toward the zero point of the dial, and in the intervals of systolic action will return by a slower movement to the starting point; this point nearly coinciding with the point at which the needle would rest if the subject were laid horizontally on the bed of the instrument. The return of the needle is effected by a series of secondary vibrations which appear to bear an appreciable but imperfect analogy to corresponding features in the sphygmograph. This phenomenon may very easily be verified, but in repeating the experiment it should be borne in mind that the following are desiderata:-That the skeleton of the subject be brought as nearly as possible into contact with the instrument and that the hipand knee-joints be so disposed as to secure the maximum possible of rigidity in a perpendicular direction. It does not appear that this phenomenon has heretofore been anticipated by any process of theorising, or turned to any useful account. It may therefore be permitted me to point out what may prove to be its phenomenal cause and practical consequences. As to its cause-When the heart is contracting it propels blood in all directions; but the greatest column is propelled downward, along the aorta, almost in the direction of the axis of the body. If, therefore, we disregard all blood that is propelled upward, and make a compensating abatement from that which is propelled downward, there will remain a certain mass of blood which at each contraction of the heart is forced